| The Linux NCR53C8XX/SYM53C8XX drivers README file | |
| Written by Gerard Roudier <[email protected]> | |
| 21 Rue Carnot | |
| 95170 DEUIL LA BARRE - FRANCE | |
| 29 May 1999 | |
| =============================================================================== | |
| 1. Introduction | |
| 2. Supported chips and SCSI features | |
| 3. Advantages of the enhanced 896 driver | |
| 3.1 Optimized SCSI SCRIPTS | |
| 3.2 New features of the SYM53C896 (64 bit PCI dual LVD SCSI controller) | |
| 4. Memory mapped I/O versus normal I/O | |
| 5. Tagged command queueing | |
| 6. Parity checking | |
| 7. Profiling information | |
| 8. Control commands | |
| 8.1 Set minimum synchronous period | |
| 8.2 Set wide size | |
| 8.3 Set maximum number of concurrent tagged commands | |
| 8.4 Set order type for tagged command | |
| 8.5 Set debug mode | |
| 8.6 Clear profile counters | |
| 8.7 Set flag (no_disc) | |
| 8.8 Set verbose level | |
| 8.9 Reset all logical units of a target | |
| 8.10 Abort all tasks of all logical units of a target | |
| 9. Configuration parameters | |
| 10. Boot setup commands | |
| 10.1 Syntax | |
| 10.2 Available arguments | |
| 10.2.1 Master parity checking | |
| 10.2.2 Scsi parity checking | |
| 10.2.3 Scsi disconnections | |
| 10.2.4 Special features | |
| 10.2.5 Ultra SCSI support | |
| 10.2.6 Default number of tagged commands | |
| 10.2.7 Default synchronous period factor | |
| 10.2.8 Negotiate synchronous with all devices | |
| 10.2.9 Verbosity level | |
| 10.2.10 Debug mode | |
| 10.2.11 Burst max | |
| 10.2.12 LED support | |
| 10.2.13 Max wide | |
| 10.2.14 Differential mode | |
| 10.2.15 IRQ mode | |
| 10.2.16 Reverse probe | |
| 10.2.17 Fix up PCI configuration space | |
| 10.2.18 Serial NVRAM | |
| 10.2.19 Check SCSI BUS | |
| 10.2.20 Exclude a host from being attached | |
| 10.2.21 Suggest a default SCSI id for hosts | |
| 10.2.22 Enable use of IMMEDIATE ARBITRATION | |
| 10.3 Advised boot setup commands | |
| 10.4 PCI configuration fix-up boot option | |
| 10.5 Serial NVRAM support boot option | |
| 10.6 SCSI BUS checking boot option | |
| 10.7 IMMEDIATE ARBITRATION boot option | |
| 11. Some constants and flags of the ncr53c8xx.h header file | |
| 12. Installation | |
| 13. Architecture dependent features | |
| 14. Known problems | |
| 14.1 Tagged commands with Iomega Jaz device | |
| 14.2 Device names change when another controller is added | |
| 14.3 Using only 8 bit devices with a WIDE SCSI controller. | |
| 14.4 Possible data corruption during a Memory Write and Invalidate | |
| 14.5 IRQ sharing problems | |
| 15. SCSI problem troubleshooting | |
| 15.1 Problem tracking | |
| 15.2 Understanding hardware error reports | |
| 16. Synchronous transfer negotiation tables | |
| 16.1 Synchronous timings for 53C875 and 53C860 Ultra-SCSI controllers | |
| 16.2 Synchronous timings for fast SCSI-2 53C8XX controllers | |
| 17. Serial NVRAM support (by Richard Waltham) | |
| 17.1 Features | |
| 17.2 Symbios NVRAM layout | |
| 17.3 Tekram NVRAM layout | |
| 18. Support for Big Endian | |
| 18.1 Big Endian CPU | |
| 18.2 NCR chip in Big Endian mode of operations | |
| =============================================================================== | |
| 1. Introduction | |
| The initial Linux ncr53c8xx driver has been a port of the ncr driver from | |
| FreeBSD that has been achieved in November 1995 by: | |
| Gerard Roudier <[email protected]> | |
| The original driver has been written for 386bsd and FreeBSD by: | |
| Wolfgang Stanglmeier <[email protected]> | |
| Stefan Esser <[email protected]> | |
| It is now available as a bundle of 2 drivers: | |
| - ncr53c8xx generic driver that supports all the SYM53C8XX family including | |
| the earliest 810 rev. 1, the latest 896 (2 channel LVD SCSI controller) and | |
| the new 895A (1 channel LVD SCSI controller). | |
| - sym53c8xx enhanced driver (a.k.a. 896 drivers) that drops support of oldest | |
| chips in order to gain advantage of new features, as LOAD/STORE instructions | |
| available since the 810A and hardware phase mismatch available with the | |
| 896 and the 895A. | |
| You can find technical information about the NCR 8xx family in the | |
| PCI-HOWTO written by Michael Will and in the SCSI-HOWTO written by | |
| Drew Eckhardt. | |
| Information about new chips is available at LSILOGIC web server: | |
| http://www.lsilogic.com/ | |
| SCSI standard documentations are available at SYMBIOS ftp server: | |
| ftp://ftp.symbios.com/ | |
| Useful SCSI tools written by Eric Youngdale are available at tsx-11: | |
| ftp://tsx-11.mit.edu/pub/linux/ALPHA/scsi/scsiinfo-X.Y.tar.gz | |
| ftp://tsx-11.mit.edu/pub/linux/ALPHA/scsi/scsidev-X.Y.tar.gz | |
| These tools are not ALPHA but quite clean and work quite well. | |
| It is essential you have the 'scsiinfo' package. | |
| This short documentation describes the features of the generic and enhanced | |
| drivers, configuration parameters and control commands available through | |
| the proc SCSI file system read / write operations. | |
| This driver has been tested OK with linux/i386, Linux/Alpha and Linux/PPC. | |
| Latest driver version and patches are available at: | |
| ftp://ftp.tux.org/pub/people/gerard-roudier | |
| or | |
| ftp://ftp.symbios.com/mirror/ftp.tux.org/pub/tux/roudier/drivers | |
| I am not a native speaker of English and there are probably lots of | |
| mistakes in this README file. Any help will be welcome. | |
| 2. Supported chips and SCSI features | |
| The following features are supported for all chips: | |
| Synchronous negotiation | |
| Disconnection | |
| Tagged command queuing | |
| SCSI parity checking | |
| Master parity checking | |
| "Wide negotiation" is supported for chips that allow it. The | |
| following table shows some characteristics of NCR 8xx family chips | |
| and what drivers support them. | |
| Supported by Supported by | |
| On board the generic the enhanced | |
| Chip SDMS BIOS Wide SCSI std. Max. sync driver driver | |
| ---- --------- ---- --------- ---------- ------------ ------------- | |
| 810 N N FAST10 10 MB/s Y N | |
| 810A N N FAST10 10 MB/s Y Y | |
| 815 Y N FAST10 10 MB/s Y N | |
| 825 Y Y FAST10 20 MB/s Y N | |
| 825A Y Y FAST10 20 MB/s Y Y | |
| 860 N N FAST20 20 MB/s Y Y | |
| 875 Y Y FAST20 40 MB/s Y Y | |
| 876 Y Y FAST20 40 MB/s Y Y | |
| 895 Y Y FAST40 80 MB/s Y Y | |
| 895A Y Y FAST40 80 MB/s Y Y | |
| 896 Y Y FAST40 80 MB/s Y Y | |
| 897 Y Y FAST40 80 MB/s Y Y | |
| 1510D Y Y FAST40 80 MB/s Y Y | |
| 1010 Y Y FAST80 160 MB/s N Y | |
| 1010_66* Y Y FAST80 160 MB/s N Y | |
| * Chip supports 33MHz and 66MHz PCI buses. | |
| Summary of other supported features: | |
| Module: allow to load the driver | |
| Memory mapped I/O: increases performance | |
| Profiling information: read operations from the proc SCSI file system | |
| Control commands: write operations to the proc SCSI file system | |
| Debugging information: written to syslog (expert only) | |
| Scatter / gather | |
| Shared interrupt | |
| Boot setup commands | |
| Serial NVRAM: Symbios and Tekram formats | |
| 3. Advantages of the enhanced 896 driver | |
| 3.1 Optimized SCSI SCRIPTS. | |
| The 810A, 825A, 875, 895, 896 and 895A support new SCSI SCRIPTS instructions | |
| named LOAD and STORE that allow to move up to 1 DWORD from/to an IO register | |
| to/from memory much faster that the MOVE MEMORY instruction that is supported | |
| by the 53c7xx and 53c8xx family. | |
| The LOAD/STORE instructions support absolute and DSA relative addressing | |
| modes. The SCSI SCRIPTS had been entirely rewritten using LOAD/STORE instead | |
| of MOVE MEMORY instructions. | |
| 3.2 New features of the SYM53C896 (64 bit PCI dual LVD SCSI controller) | |
| The 896 and the 895A allows handling of the phase mismatch context from | |
| SCRIPTS (avoids the phase mismatch interrupt that stops the SCSI processor | |
| until the C code has saved the context of the transfer). | |
| Implementing this without using LOAD/STORE instructions would be painful | |
| and I didn't even want to try it. | |
| The 896 chip supports 64 bit PCI transactions and addressing, while the | |
| 895A supports 32 bit PCI transactions and 64 bit addressing. | |
| The SCRIPTS processor of these chips is not true 64 bit, but uses segment | |
| registers for bit 32-63. Another interesting feature is that LOAD/STORE | |
| instructions that address the on-chip RAM (8k) remain internal to the chip. | |
| Due to the use of LOAD/STORE SCRIPTS instructions, this driver does not | |
| support the following chips: | |
| - SYM53C810 revision < 0x10 (16) | |
| - SYM53C815 all revisions | |
| - SYM53C825 revision < 0x10 (16) | |
| 4. Memory mapped I/O versus normal I/O | |
| Memory mapped I/O has less latency than normal I/O. Since | |
| linux-1.3.x, memory mapped I/O is used rather than normal I/O. Memory | |
| mapped I/O seems to work fine on most hardware configurations, but | |
| some poorly designed motherboards may break this feature. | |
| The configuration option CONFIG_SCSI_NCR53C8XX_IOMAPPED forces the | |
| driver to use normal I/O in all cases. | |
| 5. Tagged command queueing | |
| Queuing more than 1 command at a time to a device allows it to perform | |
| optimizations based on actual head positions and its mechanical | |
| characteristics. This feature may also reduce average command latency. | |
| In order to really gain advantage of this feature, devices must have | |
| a reasonable cache size (No miracle is to be expected for a low-end | |
| hard disk with 128 KB or less). | |
| Some known SCSI devices do not properly support tagged command queuing. | |
| Generally, firmware revisions that fix this kind of problems are available | |
| at respective vendor web/ftp sites. | |
| All I can say is that the hard disks I use on my machines behave well with | |
| this driver with tagged command queuing enabled: | |
| - IBM S12 0662 | |
| - Conner 1080S | |
| - Quantum Atlas I | |
| - Quantum Atlas II | |
| If your controller has NVRAM, you can configure this feature per target | |
| from the user setup tool. The Tekram Setup program allows to tune the | |
| maximum number of queued commands up to 32. The Symbios Setup only allows | |
| to enable or disable this feature. | |
| The maximum number of simultaneous tagged commands queued to a device | |
| is currently set to 8 by default. This value is suitable for most SCSI | |
| disks. With large SCSI disks (>= 2GB, cache >= 512KB, average seek time | |
| <= 10 ms), using a larger value may give better performances. | |
| The sym53c8xx driver supports up to 255 commands per device, and the | |
| generic ncr53c8xx driver supports up to 64, but using more than 32 is | |
| generally not worth-while, unless you are using a very large disk or disk | |
| array. It is noticeable that most of recent hard disks seem not to accept | |
| more than 64 simultaneous commands. So, using more than 64 queued commands | |
| is probably just resource wasting. | |
| If your controller does not have NVRAM or if it is managed by the SDMS | |
| BIOS/SETUP, you can configure tagged queueing feature and device queue | |
| depths from the boot command-line. For example: | |
| ncr53c8xx=tags:4/t2t3q15-t4q7/t1u0q32 | |
| will set tagged commands queue depths as follow: | |
| - target 2 all luns on controller 0 --> 15 | |
| - target 3 all luns on controller 0 --> 15 | |
| - target 4 all luns on controller 0 --> 7 | |
| - target 1 lun 0 on controller 1 --> 32 | |
| - all other target/lun --> 4 | |
| In some special conditions, some SCSI disk firmwares may return a | |
| QUEUE FULL status for a SCSI command. This behaviour is managed by the | |
| driver using the following heuristic: | |
| - Each time a QUEUE FULL status is returned, tagged queue depth is reduced | |
| to the actual number of disconnected commands. | |
| - Every 1000 successfully completed SCSI commands, if allowed by the | |
| current limit, the maximum number of queueable commands is incremented. | |
| Since QUEUE FULL status reception and handling is resource wasting, the | |
| driver notifies by default this problem to user by indicating the actual | |
| number of commands used and their status, as well as its decision on the | |
| device queue depth change. | |
| The heuristic used by the driver in handling QUEUE FULL ensures that the | |
| impact on performances is not too bad. You can get rid of the messages by | |
| setting verbose level to zero, as follow: | |
| 1st method: boot your system using 'ncr53c8xx=verb:0' option. | |
| 2nd method: apply "setverbose 0" control command to the proc fs entry | |
| corresponding to your controller after boot-up. | |
| 6. Parity checking | |
| The driver supports SCSI parity checking and PCI bus master parity | |
| checking. These features must be enabled in order to ensure safe data | |
| transfers. However, some flawed devices or mother boards will have | |
| problems with parity. You can disable either PCI parity or SCSI parity | |
| checking by entering appropriate options from the boot command line. | |
| (See 10: Boot setup commands). | |
| 7. Profiling information | |
| Profiling information is available through the proc SCSI file system. | |
| Since gathering profiling information may impact performances, this | |
| feature is disabled by default and requires a compilation configuration | |
| option to be set to Y. | |
| The device associated with a host has the following pathname: | |
| /proc/scsi/ncr53c8xx/N (N=0,1,2 ....) | |
| Generally, only 1 board is used on hardware configuration, and that device is: | |
| /proc/scsi/ncr53c8xx/0 | |
| However, if the driver has been made as module, the number of the | |
| hosts is incremented each time the driver is loaded. | |
| In order to display profiling information, just enter: | |
| cat /proc/scsi/ncr53c8xx/0 | |
| and you will get something like the following text: | |
| ------------------------------------------------------- | |
| General information: | |
| Chip NCR53C810, device id 0x1, revision id 0x2 | |
| IO port address 0x6000, IRQ number 10 | |
| Using memory mapped IO at virtual address 0x282c000 | |
| Synchronous transfer period 25, max commands per lun 4 | |
| Profiling information: | |
| num_trans = 18014 | |
| num_kbytes = 671314 | |
| num_disc = 25763 | |
| num_break = 1673 | |
| num_int = 1685 | |
| num_fly = 18038 | |
| ms_setup = 4940 | |
| ms_data = 369940 | |
| ms_disc = 183090 | |
| ms_post = 1320 | |
| ------------------------------------------------------- | |
| General information is easy to understand. The device ID and the | |
| revision ID identify the SCSI chip as follows: | |
| Chip Device id Revision Id | |
| ---- --------- ----------- | |
| 810 0x1 < 0x10 | |
| 810A 0x1 >= 0x10 | |
| 815 0x4 | |
| 825 0x3 < 0x10 | |
| 860 0x6 | |
| 825A 0x3 >= 0x10 | |
| 875 0xf | |
| 895 0xc | |
| The profiling information is updated upon completion of SCSI commands. | |
| A data structure is allocated and zeroed when the host adapter is | |
| attached. So, if the driver is a module, the profile counters are | |
| cleared each time the driver is loaded. The "clearprof" command | |
| allows you to clear these counters at any time. | |
| The following counters are available: | |
| ("num" prefix means "number of", | |
| "ms" means milli-seconds) | |
| num_trans | |
| Number of completed commands | |
| Example above: 18014 completed commands | |
| num_kbytes | |
| Number of kbytes transferred | |
| Example above: 671 MB transferred | |
| num_disc | |
| Number of SCSI disconnections | |
| Example above: 25763 SCSI disconnections | |
| num_break | |
| number of script interruptions (phase mismatch) | |
| Example above: 1673 script interruptions | |
| num_int | |
| Number of interrupts other than "on the fly" | |
| Example above: 1685 interruptions not "on the fly" | |
| num_fly | |
| Number of interrupts "on the fly" | |
| Example above: 18038 interruptions "on the fly" | |
| ms_setup | |
| Elapsed time for SCSI commands setups | |
| Example above: 4.94 seconds | |
| ms_data | |
| Elapsed time for data transfers | |
| Example above: 369.94 seconds spent for data transfer | |
| ms_disc | |
| Elapsed time for SCSI disconnections | |
| Example above: 183.09 seconds spent disconnected | |
| ms_post | |
| Elapsed time for command post processing | |
| (time from SCSI status get to command completion call) | |
| Example above: 1.32 seconds spent for post processing | |
| Due to the 1/100 second tick of the system clock, "ms_post" time may | |
| be wrong. | |
| In the example above, we got 18038 interrupts "on the fly" and only | |
| 1673 script breaks generally due to disconnections inside a segment | |
| of the scatter list. | |
| 8. Control commands | |
| Control commands can be sent to the driver with write operations to | |
| the proc SCSI file system. The generic command syntax is the | |
| following: | |
| echo "<verb> <parameters>" >/proc/scsi/ncr53c8xx/0 | |
| (assumes controller number is 0) | |
| Using "all" for "<target>" parameter with the commands below will | |
| apply to all targets of the SCSI chain (except the controller). | |
| Available commands: | |
| 8.1 Set minimum synchronous period factor | |
| setsync <target> <period factor> | |
| target: target number | |
| period: minimum synchronous period. | |
| Maximum speed = 1000/(4*period factor) except for special | |
| cases below. | |
| Specify a period of 255, to force asynchronous transfer mode. | |
| 10 means 25 nano-seconds synchronous period | |
| 11 means 30 nano-seconds synchronous period | |
| 12 means 50 nano-seconds synchronous period | |
| 8.2 Set wide size | |
| setwide <target> <size> | |
| target: target number | |
| size: 0=8 bits, 1=16bits | |
| 8.3 Set maximum number of concurrent tagged commands | |
| settags <target> <tags> | |
| target: target number | |
| tags: number of concurrent tagged commands | |
| must not be greater than SCSI_NCR_MAX_TAGS (default: 8) | |
| 8.4 Set order type for tagged command | |
| setorder <order> | |
| order: 3 possible values: | |
| simple: use SIMPLE TAG for all operations (read and write) | |
| ordered: use ORDERED TAG for all operations | |
| default: use default tag type, | |
| SIMPLE TAG for read operations | |
| ORDERED TAG for write operations | |
| 8.5 Set debug mode | |
| setdebug <list of debug flags> | |
| Available debug flags: | |
| alloc: print info about memory allocations (ccb, lcb) | |
| queue: print info about insertions into the command start queue | |
| result: print sense data on CHECK CONDITION status | |
| scatter: print info about the scatter process | |
| scripts: print info about the script binding process | |
| tiny: print minimal debugging information | |
| timing: print timing information of the NCR chip | |
| nego: print information about SCSI negotiations | |
| phase: print information on script interruptions | |
| Use "setdebug" with no argument to reset debug flags. | |
| 8.6 Clear profile counters | |
| clearprof | |
| The profile counters are automatically cleared when the amount of | |
| data transferred reaches 1000 GB in order to avoid overflow. | |
| The "clearprof" command allows you to clear these counters at any time. | |
| 8.7 Set flag (no_disc) | |
| setflag <target> <flag> | |
| target: target number | |
| For the moment, only one flag is available: | |
| no_disc: not allow target to disconnect. | |
| Do not specify any flag in order to reset the flag. For example: | |
| - setflag 4 | |
| will reset no_disc flag for target 4, so will allow it disconnections. | |
| - setflag all | |
| will allow disconnection for all devices on the SCSI bus. | |
| 8.8 Set verbose level | |
| setverbose #level | |
| The driver default verbose level is 1. This command allows to change | |
| th driver verbose level after boot-up. | |
| 8.9 Reset all logical units of a target | |
| resetdev <target> | |
| target: target number | |
| The driver will try to send a BUS DEVICE RESET message to the target. | |
| (Only supported by the SYM53C8XX driver and provided for test purpose) | |
| 8.10 Abort all tasks of all logical units of a target | |
| cleardev <target> | |
| target: target number | |
| The driver will try to send a ABORT message to all the logical units | |
| of the target. | |
| (Only supported by the SYM53C8XX driver and provided for test purpose) | |
| 9. Configuration parameters | |
| If the firmware of all your devices is perfect enough, all the | |
| features supported by the driver can be enabled at start-up. However, | |
| if only one has a flaw for some SCSI feature, you can disable the | |
| support by the driver of this feature at linux start-up and enable | |
| this feature after boot-up only for devices that support it safely. | |
| CONFIG_SCSI_NCR53C8XX_IOMAPPED (default answer: n) | |
| Answer "y" if you suspect your mother board to not allow memory mapped I/O. | |
| May slow down performance a little. This option is required by | |
| Linux/PPC and is used no matter what you select here. Linux/PPC | |
| suffers no performance loss with this option since all IO is memory | |
| mapped anyway. | |
| CONFIG_SCSI_NCR53C8XX_DEFAULT_TAGS (default answer: 8) | |
| Default tagged command queue depth. | |
| CONFIG_SCSI_NCR53C8XX_MAX_TAGS (default answer: 8) | |
| This option allows you to specify the maximum number of tagged commands | |
| that can be queued to a device. The maximum supported value is 32. | |
| CONFIG_SCSI_NCR53C8XX_SYNC (default answer: 5) | |
| This option allows you to specify the frequency in MHz the driver | |
| will use at boot time for synchronous data transfer negotiations. | |
| This frequency can be changed later with the "setsync" control command. | |
| 0 means "asynchronous data transfers". | |
| CONFIG_SCSI_NCR53C8XX_FORCE_SYNC_NEGO (default answer: n) | |
| Force synchronous negotiation for all SCSI-2 devices. | |
| Some SCSI-2 devices do not report this feature in byte 7 of inquiry | |
| response but do support it properly (TAMARACK scanners for example). | |
| CONFIG_SCSI_NCR53C8XX_NO_DISCONNECT (default and only reasonable answer: n) | |
| If you suspect a device of yours does not properly support disconnections, | |
| you can answer "y". Then, all SCSI devices will never disconnect the bus | |
| even while performing long SCSI operations. | |
| CONFIG_SCSI_NCR53C8XX_SYMBIOS_COMPAT | |
| Genuine SYMBIOS boards use GPIO0 in output for controller LED and GPIO3 | |
| bit as a flag indicating singled-ended/differential interface. | |
| If all the boards of your system are genuine SYMBIOS boards or use | |
| BIOS and drivers from SYMBIOS, you would want to enable this option. | |
| This option must NOT be enabled if your system has at least one 53C8XX | |
| based scsi board with a vendor-specific BIOS. | |
| For example, Tekram DC-390/U, DC-390/W and DC-390/F scsi controllers | |
| use a vendor-specific BIOS and are known to not use SYMBIOS compatible | |
| GPIO wiring. So, this option must not be enabled if your system has | |
| such a board installed. | |
| CONFIG_SCSI_NCR53C8XX_NVRAM_DETECT | |
| Enable support for reading the serial NVRAM data on Symbios and | |
| some Symbios compatible cards, and Tekram DC390W/U/F cards. Useful for | |
| systems with more than one Symbios compatible controller where at least | |
| one has a serial NVRAM, or for a system with a mixture of Symbios and | |
| Tekram cards. Enables setting the boot order of host adaptors | |
| to something other than the default order or "reverse probe" order. | |
| Also enables Symbios and Tekram cards to be distinguished so | |
| CONFIG_SCSI_NCR53C8XX_SYMBIOS_COMPAT may be set in a system with a | |
| mixture of Symbios and Tekram cards so the Symbios cards can make use of | |
| the full range of Symbios features, differential, led pin, without | |
| causing problems for the Tekram card(s). | |
| 10. Boot setup commands | |
| 10.1 Syntax | |
| Setup commands can be passed to the driver either at boot time or as a | |
| string variable using 'insmod'. | |
| A boot setup command for the ncr53c8xx (sym53c8xx) driver begins with the | |
| driver name "ncr53c8xx="(sym53c8xx). The kernel syntax parser then expects | |
| an optional list of integers separated with comma followed by an optional | |
| list of comma-separated strings. Example of boot setup command under lilo | |
| prompt: | |
| lilo: linux root=/dev/hda2 ncr53c8xx=tags:4,sync:10,debug:0x200 | |
| - enable tagged commands, up to 4 tagged commands queued. | |
| - set synchronous negotiation speed to 10 Mega-transfers / second. | |
| - set DEBUG_NEGO flag. | |
| Since comma seems not to be allowed when defining a string variable using | |
| 'insmod', the driver also accepts <space> as option separator. | |
| The following command will install driver module with the same options as | |
| above. | |
| insmod ncr53c8xx.o ncr53c8xx="tags:4 sync:10 debug:0x200" | |
| For the moment, the integer list of arguments is discarded by the driver. | |
| It will be used in the future in order to allow a per controller setup. | |
| Each string argument must be specified as "keyword:value". Only lower-case | |
| characters and digits are allowed. | |
| In a system that contains multiple 53C8xx adapters insmod will install the | |
| specified driver on each adapter. To exclude a chip use the 'excl' keyword. | |
| The sequence of commands, | |
| insmod sym53c8xx sym53c8xx=excl:0x1400 | |
| insmod ncr53c8xx | |
| installs the sym53c8xx driver on all adapters except the one at IO port | |
| address 0x1400 and then installs the ncr53c8xx driver to the adapter at IO | |
| port address 0x1400. | |
| 10.2 Available arguments | |
| 10.2.1 Master parity checking | |
| mpar:y enabled | |
| mpar:n disabled | |
| 10.2.2 Scsi parity checking | |
| spar:y enabled | |
| spar:n disabled | |
| 10.2.3 Scsi disconnections | |
| disc:y enabled | |
| disc:n disabled | |
| 10.2.4 Special features | |
| Only apply to 810A, 825A, 860, 875 and 895 controllers. | |
| Have no effect with other ones. | |
| specf:y (or 1) enabled | |
| specf:n (or 0) disabled | |
| specf:3 enabled except Memory Write And Invalidate | |
| The default driver setup is 'specf:3'. As a consequence, option 'specf:y' | |
| must be specified in the boot setup command to enable Memory Write And | |
| Invalidate. | |
| 10.2.5 Ultra SCSI support | |
| Only apply to 860, 875, 895, 895a, 896, 1010 and 1010_66 controllers. | |
| Have no effect with other ones. | |
| ultra:n All ultra speeds enabled | |
| ultra:2 Ultra2 enabled | |
| ultra:1 Ultra enabled | |
| ultra:0 Ultra speeds disabled | |
| 10.2.6 Default number of tagged commands | |
| tags:0 (or tags:1 ) tagged command queuing disabled | |
| tags:#tags (#tags > 1) tagged command queuing enabled | |
| #tags will be truncated to the max queued commands configuration parameter. | |
| This option also allows to specify a command queue depth for each device | |
| that support tagged command queueing. | |
| Example: | |
| ncr53c8xx=tags:10/t2t3q16-t5q24/t1u2q32 | |
| will set devices queue depth as follow: | |
| - controller #0 target #2 and target #3 -> 16 commands, | |
| - controller #0 target #5 -> 24 commands, | |
| - controller #1 target #1 logical unit #2 -> 32 commands, | |
| - all other logical units (all targets, all controllers) -> 10 commands. | |
| 10.2.7 Default synchronous period factor | |
| sync:255 disabled (asynchronous transfer mode) | |
| sync:#factor | |
| #factor = 10 Ultra-2 SCSI 40 Mega-transfers / second | |
| #factor = 11 Ultra-2 SCSI 33 Mega-transfers / second | |
| #factor < 25 Ultra SCSI 20 Mega-transfers / second | |
| #factor < 50 Fast SCSI-2 | |
| In all cases, the driver will use the minimum transfer period supported by | |
| controllers according to NCR53C8XX chip type. | |
| 10.2.8 Negotiate synchronous with all devices | |
| (force sync nego) | |
| fsn:y enabled | |
| fsn:n disabled | |
| 10.2.9 Verbosity level | |
| verb:0 minimal | |
| verb:1 normal | |
| verb:2 too much | |
| 10.2.10 Debug mode | |
| debug:0 clear debug flags | |
| debug:#x set debug flags | |
| #x is an integer value combining the following power-of-2 values: | |
| DEBUG_ALLOC 0x1 | |
| DEBUG_PHASE 0x2 | |
| DEBUG_POLL 0x4 | |
| DEBUG_QUEUE 0x8 | |
| DEBUG_RESULT 0x10 | |
| DEBUG_SCATTER 0x20 | |
| DEBUG_SCRIPT 0x40 | |
| DEBUG_TINY 0x80 | |
| DEBUG_TIMING 0x100 | |
| DEBUG_NEGO 0x200 | |
| DEBUG_TAGS 0x400 | |
| DEBUG_FREEZE 0x800 | |
| DEBUG_RESTART 0x1000 | |
| You can play safely with DEBUG_NEGO. However, some of these flags may | |
| generate bunches of syslog messages. | |
| 10.2.11 Burst max | |
| burst:0 burst disabled | |
| burst:255 get burst length from initial IO register settings. | |
| burst:#x burst enabled (1<<#x burst transfers max) | |
| #x is an integer value which is log base 2 of the burst transfers max. | |
| The NCR53C875 and NCR53C825A support up to 128 burst transfers (#x = 7). | |
| Other chips only support up to 16 (#x = 4). | |
| This is a maximum value. The driver set the burst length according to chip | |
| and revision ids. By default the driver uses the maximum value supported | |
| by the chip. | |
| 10.2.12 LED support | |
| led:1 enable LED support | |
| led:0 disable LED support | |
| Donnot enable LED support if your scsi board does not use SDMS BIOS. | |
| (See 'Configuration parameters') | |
| 10.2.13 Max wide | |
| wide:1 wide scsi enabled | |
| wide:0 wide scsi disabled | |
| Some scsi boards use a 875 (ultra wide) and only supply narrow connectors. | |
| If you have connected a wide device with a 50 pins to 68 pins cable | |
| converter, any accepted wide negotiation will break further data transfers. | |
| In such a case, using "wide:0" in the bootup command will be helpful. | |
| 10.2.14 Differential mode | |
| diff:0 never set up diff mode | |
| diff:1 set up diff mode if BIOS set it | |
| diff:2 always set up diff mode | |
| diff:3 set diff mode if GPIO3 is not set | |
| 10.2.15 IRQ mode | |
| irqm:0 always open drain | |
| irqm:1 same as initial settings (assumed BIOS settings) | |
| irqm:2 always totem pole | |
| irqm:0x10 driver will not use IRQF_SHARED flag when requesting irq | |
| (Bits 0x10 and 0x20 can be combined with hardware irq mode option) | |
| 10.2.16 Reverse probe | |
| revprob:n probe chip ids from the PCI configuration in this order: | |
| 810, 815, 820, 860, 875, 885, 895, 896 | |
| revprob:y probe chip ids in the reverse order. | |
| 10.2.17 Fix up PCI configuration space | |
| pcifix:<option bits> | |
| Available option bits: | |
| 0x0: No attempt to fix PCI configuration space registers values. | |
| 0x1: Set PCI cache-line size register if not set. | |
| 0x2: Set write and invalidate bit in PCI command register. | |
| 0x4: Increase if necessary PCI latency timer according to burst max. | |
| Use 'pcifix:7' in order to allow the driver to fix up all PCI features. | |
| 10.2.18 Serial NVRAM | |
| nvram:n do not look for serial NVRAM | |
| nvram:y test controllers for onboard serial NVRAM | |
| (alternate binary form) | |
| mvram=<bits options> | |
| 0x01 look for NVRAM (equivalent to nvram=y) | |
| 0x02 ignore NVRAM "Synchronous negotiation" parameters for all devices | |
| 0x04 ignore NVRAM "Wide negotiation" parameter for all devices | |
| 0x08 ignore NVRAM "Scan at boot time" parameter for all devices | |
| 0x80 also attach controllers set to OFF in the NVRAM (sym53c8xx only) | |
| 10.2.19 Check SCSI BUS | |
| buschk:<option bits> | |
| Available option bits: | |
| 0x0: No check. | |
| 0x1: Check and do not attach the controller on error. | |
| 0x2: Check and just warn on error. | |
| 0x4: Disable SCSI bus integrity checking. | |
| 10.2.20 Exclude a host from being attached | |
| excl=<io_address> | |
| Prevent host at a given io address from being attached. | |
| For example 'ncr53c8xx=excl:0xb400,excl:0xc000' indicate to the | |
| ncr53c8xx driver not to attach hosts at address 0xb400 and 0xc000. | |
| 10.2.21 Suggest a default SCSI id for hosts | |
| hostid:255 no id suggested. | |
| hostid:#x (0 < x < 7) x suggested for hosts SCSI id. | |
| If a host SCSI id is available from the NVRAM, the driver will ignore | |
| any value suggested as boot option. Otherwise, if a suggested value | |
| different from 255 has been supplied, it will use it. Otherwise, it will | |
| try to deduce the value previously set in the hardware and use value | |
| 7 if the hardware value is zero. | |
| 10.2.22 Enable use of IMMEDIATE ARBITRATION | |
| (only supported by the sym53c8xx driver. See 10.7 for more details) | |
| iarb:0 do not use this feature. | |
| iarb:#x use this feature according to bit fields as follow: | |
| bit 0 (1) : enable IARB each time the initiator has been reselected | |
| when it arbitrated for the SCSI BUS. | |
| (#x >> 4) : maximum number of successive settings of IARB if the initiator | |
| win arbitration and it has other commands to send to a device. | |
| Boot fail safe | |
| safe:y load the following assumed fail safe initial setup | |
| master parity disabled mpar:n | |
| scsi parity enabled spar:y | |
| disconnections not allowed disc:n | |
| special features disabled specf:n | |
| ultra scsi disabled ultra:n | |
| force sync negotiation disabled fsn:n | |
| reverse probe disabled revprob:n | |
| PCI fix up disabled pcifix:0 | |
| serial NVRAM enabled nvram:y | |
| verbosity level 2 verb:2 | |
| tagged command queuing disabled tags:0 | |
| synchronous negotiation disabled sync:255 | |
| debug flags none debug:0 | |
| burst length from BIOS settings burst:255 | |
| LED support disabled led:0 | |
| wide support disabled wide:0 | |
| settle time 10 seconds settle:10 | |
| differential support from BIOS settings diff:1 | |
| irq mode from BIOS settings irqm:1 | |
| SCSI BUS check do not attach on error buschk:1 | |
| immediate arbitration disabled iarb:0 | |
| 10.3 Advised boot setup commands | |
| If the driver has been configured with default options, the equivalent | |
| boot setup is: | |
| ncr53c8xx=mpar:y,spar:y,disc:y,specf:3,fsn:n,ultra:2,fsn:n,revprob:n,verb:1\ | |
| tags:0,sync:50,debug:0,burst:7,led:0,wide:1,settle:2,diff:0,irqm:0 | |
| For an installation diskette or a safe but not fast system, | |
| boot setup can be: | |
| ncr53c8xx=safe:y,mpar:y,disc:y | |
| ncr53c8xx=safe:y,disc:y | |
| ncr53c8xx=safe:y,mpar:y | |
| ncr53c8xx=safe:y | |
| My personal system works flawlessly with the following equivalent setup: | |
| ncr53c8xx=mpar:y,spar:y,disc:y,specf:1,fsn:n,ultra:2,fsn:n,revprob:n,verb:1\ | |
| tags:32,sync:12,debug:0,burst:7,led:1,wide:1,settle:2,diff:0,irqm:0 | |
| The driver prints its actual setup when verbosity level is 2. You can try | |
| "ncr53c8xx=verb:2" to get the "static" setup of the driver, or add "verb:2" | |
| to your boot setup command in order to check the actual setup the driver is | |
| using. | |
| 10.4 PCI configuration fix-up boot option | |
| pcifix:<option bits> | |
| Available option bits: | |
| 0x1: Set PCI cache-line size register if not set. | |
| 0x2: Set write and invalidate bit in PCI command register. | |
| Use 'pcifix:3' in order to allow the driver to fix both PCI features. | |
| These options only apply to new SYMBIOS chips 810A, 825A, 860, 875 | |
| and 895 and are only supported for Pentium and 486 class processors. | |
| Recent SYMBIOS 53C8XX scsi processors are able to use PCI read multiple | |
| and PCI write and invalidate commands. These features require the | |
| cache line size register to be properly set in the PCI configuration | |
| space of the chips. On the other hand, chips will use PCI write and | |
| invalidate commands only if the corresponding bit is set to 1 in the | |
| PCI command register. | |
| Not all PCI bioses set the PCI cache line register and the PCI write and | |
| invalidate bit in the PCI configuration space of 53C8XX chips. | |
| Optimized PCI accesses may be broken for some PCI/memory controllers or | |
| make problems with some PCI boards. | |
| This fix-up worked flawlessly on my previous system. | |
| (MB Triton HX / 53C875 / 53C810A) | |
| I use these options at my own risks as you will do if you decide to | |
| use them too. | |
| 10.5 Serial NVRAM support boot option | |
| nvram:n do not look for serial NVRAM | |
| nvram:y test controllers for onboard serial NVRAM | |
| This option can also been entered as an hexadecimal value that allows | |
| to control what information the driver will get from the NVRAM and what | |
| information it will ignore. | |
| For details see '17. Serial NVRAM support'. | |
| When this option is enabled, the driver tries to detect all boards using | |
| a Serial NVRAM. This memory is used to hold user set up parameters. | |
| The parameters the driver is able to get from the NVRAM depend on the | |
| data format used, as follow: | |
| Tekram format Symbios format | |
| General and host parameters | |
| Boot order N Y | |
| Host SCSI ID Y Y | |
| SCSI parity checking Y Y | |
| Verbose boot messages N Y | |
| SCSI devices parameters | |
| Synchronous transfer speed Y Y | |
| Wide 16 / Narrow Y Y | |
| Tagged Command Queuing enabled Y Y | |
| Disconnections enabled Y Y | |
| Scan at boot time N Y | |
| In order to speed up the system boot, for each device configured without | |
| the "scan at boot time" option, the driver forces an error on the | |
| first TEST UNIT READY command received for this device. | |
| Some SDMS BIOS revisions seem to be unable to boot cleanly with very fast | |
| hard disks. In such a situation you cannot configure the NVRAM with | |
| optimized parameters value. | |
| The 'nvram' boot option can be entered in hexadecimal form in order | |
| to ignore some options configured in the NVRAM, as follow: | |
| mvram=<bits options> | |
| 0x01 look for NVRAM (equivalent to nvram=y) | |
| 0x02 ignore NVRAM "Synchronous negotiation" parameters for all devices | |
| 0x04 ignore NVRAM "Wide negotiation" parameter for all devices | |
| 0x08 ignore NVRAM "Scan at boot time" parameter for all devices | |
| 0x80 also attach controllers set to OFF in the NVRAM (sym53c8xx only) | |
| Option 0x80 is only supported by the sym53c8xx driver and is disabled by | |
| default. Result is that, by default (option not set), the sym53c8xx driver | |
| will not attach controllers set to OFF in the NVRAM. | |
| The ncr53c8xx always tries to attach all the controllers. Option 0x80 has | |
| not been added to the ncr53c8xx driver, since it has been reported to | |
| confuse users who use this driver since a long time. If you desire a | |
| controller not to be attached by the ncr53c8xx driver at Linux boot, you | |
| must use the 'excl' driver boot option. | |
| 10.6 SCSI BUS checking boot option. | |
| When this option is set to a non-zero value, the driver checks SCSI lines | |
| logic state, 100 micro-seconds after having asserted the SCSI RESET line. | |
| The driver just reads SCSI lines and checks all lines read FALSE except RESET. | |
| Since SCSI devices shall release the BUS at most 800 nano-seconds after SCSI | |
| RESET has been asserted, any signal to TRUE may indicate a SCSI BUS problem. | |
| Unfortunately, the following common SCSI BUS problems are not detected: | |
| - Only 1 terminator installed. | |
| - Misplaced terminators. | |
| - Bad quality terminators. | |
| On the other hand, either bad cabling, broken devices, not conformant | |
| devices, ... may cause a SCSI signal to be wrong when te driver reads it. | |
| 10.7 IMMEDIATE ARBITRATION boot option | |
| This option is only supported by the SYM53C8XX driver (not by the NCR53C8XX). | |
| SYMBIOS 53C8XX chips are able to arbitrate for the SCSI BUS as soon as they | |
| have detected an expected disconnection (BUS FREE PHASE). For this process | |
| to be started, bit 1 of SCNTL1 IO register must be set when the chip is | |
| connected to the SCSI BUS. | |
| When this feature has been enabled for the current connection, the chip has | |
| every chance to win arbitration if only devices with lower priority are | |
| competing for the SCSI BUS. By the way, when the chip is using SCSI id 7, | |
| then it will for sure win the next SCSI BUS arbitration. | |
| Since, there is no way to know what devices are trying to arbitrate for the | |
| BUS, using this feature can be extremely unfair. So, you are not advised | |
| to enable it, or at most enable this feature for the case the chip lost | |
| the previous arbitration (boot option 'iarb:1'). | |
| This feature has the following advantages: | |
| a) Allow the initiator with ID 7 to win arbitration when it wants so. | |
| b) Overlap at least 4 micro-seconds of arbitration time with the execution | |
| of SCRIPTS that deal with the end of the current connection and that | |
| starts the next job. | |
| Hmmm... But (a) may just prevent other devices from reselecting the initiator, | |
| and delay data transfers or status/completions, and (b) may just waste | |
| SCSI BUS bandwidth if the SCRIPTS execution lasts more than 4 micro-seconds. | |
| The use of IARB needs the SCSI_NCR_IARB_SUPPORT option to have been defined | |
| at compile time and the 'iarb' boot option to have been set to a non zero | |
| value at boot time. It is not that useful for real work, but can be used | |
| to stress SCSI devices or for some applications that can gain advantage of | |
| it. By the way, if you experience badnesses like 'unexpected disconnections', | |
| 'bad reselections', etc... when using IARB on heavy IO load, you should not | |
| be surprised, because force-feeding anything and blocking its arse at the | |
| same time cannot work for a long time. :-)) | |
| 11. Some constants and flags of the ncr53c8xx.h header file | |
| Some of these are defined from the configuration parameters. To | |
| change other "defines", you must edit the header file. Do that only | |
| if you know what you are doing. | |
| SCSI_NCR_SETUP_SPECIAL_FEATURES (default: defined) | |
| If defined, the driver will enable some special features according | |
| to chip and revision id. | |
| For 810A, 860, 825A, 875 and 895 scsi chips, this option enables | |
| support of features that reduce load of PCI bus and memory accesses | |
| during scsi transfer processing: burst op-code fetch, read multiple, | |
| read line, prefetch, cache line, write and invalidate, | |
| burst 128 (875 only), large dma fifo (875 only), offset 16 (875 only). | |
| Can be changed by the following boot setup command: | |
| ncr53c8xx=specf:n | |
| SCSI_NCR_IOMAPPED (default: not defined) | |
| If defined, normal I/O is forced. | |
| SCSI_NCR_SHARE_IRQ (default: defined) | |
| If defined, request shared IRQ. | |
| SCSI_NCR_MAX_TAGS (default: 8) | |
| Maximum number of simultaneous tagged commands to a device. | |
| Can be changed by "settags <target> <maxtags>" | |
| SCSI_NCR_SETUP_DEFAULT_SYNC (default: 50) | |
| Transfer period factor the driver will use at boot time for synchronous | |
| negotiation. 0 means asynchronous. | |
| Can be changed by "setsync <target> <period factor>" | |
| SCSI_NCR_SETUP_DEFAULT_TAGS (default: 8) | |
| Default number of simultaneous tagged commands to a device. | |
| < 1 means tagged command queuing disabled at start-up. | |
| SCSI_NCR_ALWAYS_SIMPLE_TAG (default: defined) | |
| Use SIMPLE TAG for read and write commands. | |
| Can be changed by "setorder <ordered|simple|default>" | |
| SCSI_NCR_SETUP_DISCONNECTION (default: defined) | |
| If defined, targets are allowed to disconnect. | |
| SCSI_NCR_SETUP_FORCE_SYNC_NEGO (default: not defined) | |
| If defined, synchronous negotiation is tried for all SCSI-2 devices. | |
| Can be changed by "setsync <target> <period>" | |
| SCSI_NCR_SETUP_MASTER_PARITY (default: defined) | |
| If defined, master parity checking is enabled. | |
| SCSI_NCR_SETUP_SCSI_PARITY (default: defined) | |
| If defined, SCSI parity checking is enabled. | |
| SCSI_NCR_PROFILE_SUPPORT (default: not defined) | |
| If defined, profiling information is gathered. | |
| SCSI_NCR_MAX_SCATTER (default: 128) | |
| Scatter list size of the driver ccb. | |
| SCSI_NCR_MAX_TARGET (default: 16) | |
| Max number of targets per host. | |
| SCSI_NCR_MAX_HOST (default: 2) | |
| Max number of host controllers. | |
| SCSI_NCR_SETTLE_TIME (default: 2) | |
| Number of seconds the driver will wait after reset. | |
| SCSI_NCR_TIMEOUT_ALERT (default: 3) | |
| If a pending command will time out after this amount of seconds, | |
| an ordered tag is used for the next command. | |
| Avoids timeouts for unordered tagged commands. | |
| SCSI_NCR_CAN_QUEUE (default: 7*SCSI_NCR_MAX_TAGS) | |
| Max number of commands that can be queued to a host. | |
| SCSI_NCR_CMD_PER_LUN (default: SCSI_NCR_MAX_TAGS) | |
| Max number of commands queued to a host for a device. | |
| SCSI_NCR_SG_TABLESIZE (default: SCSI_NCR_MAX_SCATTER-1) | |
| Max size of the Linux scatter/gather list. | |
| SCSI_NCR_MAX_LUN (default: 8) | |
| Max number of LUNs per target. | |
| 12. Installation | |
| This driver is part of the linux kernel distribution. | |
| Driver files are located in the sub-directory "drivers/scsi" of the | |
| kernel source tree. | |
| Driver files: | |
| README.ncr53c8xx : this file | |
| ChangeLog.ncr53c8xx : change log | |
| ncr53c8xx.h : definitions | |
| ncr53c8xx.c : the driver code | |
| New driver versions are made available separately in order to allow testing | |
| changes and new features prior to including them into the linux kernel | |
| distribution. The following URL provides information on latest available | |
| patches: | |
| ftp://ftp.tux.org/pub/people/gerard-roudier/README | |
| 13. Architecture dependent features. | |
| <Not yet written> | |
| 14. Known problems | |
| 14.1 Tagged commands with Iomega Jaz device | |
| I have not tried this device, however it has been reported to me the | |
| following: This device is capable of Tagged command queuing. However | |
| while spinning up, it rejects Tagged commands. This behaviour is | |
| conforms to 6.8.2 of SCSI-2 specifications. The current behaviour of | |
| the driver in that situation is not satisfying. So do not enable | |
| Tagged command queuing for devices that are able to spin down. The | |
| other problem that may appear is timeouts. The only way to avoid | |
| timeouts seems to edit linux/drivers/scsi/sd.c and to increase the | |
| current timeout values. | |
| 14.2 Device names change when another controller is added. | |
| When you add a new NCR53C8XX chip based controller to a system that already | |
| has one or more controllers of this family, it may happen that the order | |
| the driver registers them to the kernel causes problems due to device | |
| name changes. | |
| When at least one controller uses NvRAM, SDMS BIOS version 4 allows you to | |
| define the order the BIOS will scan the scsi boards. The driver attaches | |
| controllers according to BIOS information if NvRAM detect option is set. | |
| If your controllers do not have NvRAM, you can: | |
| - Ask the driver to probe chip ids in reverse order from the boot command | |
| line: ncr53c8xx=revprob:y | |
| - Make appropriate changes in the fstab. | |
| - Use the 'scsidev' tool from Eric Youngdale. | |
| 14.3 Using only 8 bit devices with a WIDE SCSI controller. | |
| When only 8 bit NARROW devices are connected to a 16 bit WIDE SCSI controller, | |
| you must ensure that lines of the wide part of the SCSI BUS are pulled-up. | |
| This can be achieved by ENABLING the WIDE TERMINATOR portion of the SCSI | |
| controller card. | |
| The TYAN 1365 documentation revision 1.2 is not correct about such settings. | |
| (page 10, figure 3.3). | |
| 14.4 Possible data corruption during a Memory Write and Invalidate | |
| This problem is described in SYMBIOS DEL 397, Part Number 69-039241, ITEM 4. | |
| In some complex situations, 53C875 chips revision <= 3 may start a PCI | |
| Write and Invalidate Command at a not cache-line-aligned 4 DWORDS boundary. | |
| This is only possible when Cache Line Size is 8 DWORDS or greater. | |
| Pentium systems use a 8 DWORDS cache line size and so are concerned by | |
| this chip bug, unlike i486 systems that use a 4 DWORDS cache line size. | |
| When this situation occurs, the chip may complete the Write and Invalidate | |
| command after having only filled part of the last cache line involved in | |
| the transfer, leaving to data corruption the remainder of this cache line. | |
| Not using Write And Invalidate obviously gets rid of this chip bug, and so | |
| it is now the default setting of the driver. | |
| However, for people like me who want to enable this feature, I have added | |
| part of a work-around suggested by SYMBIOS. This work-around resets the | |
| addressing logic when the DATA IN phase is entered and so prevents the bug | |
| from being triggered for the first SCSI MOVE of the phase. This work-around | |
| should be enough according to the following: | |
| The only driver internal data structure that is greater than 8 DWORDS and | |
| that is moved by the SCRIPTS processor is the 'CCB header' that contains | |
| the context of the SCSI transfer. This data structure is aligned on 8 DWORDS | |
| boundary (Pentium Cache Line Size), and so is immune to this chip bug, at | |
| least on Pentium systems. | |
| But the conditions of this bug can be met when a SCSI read command is | |
| performed using a buffer that is 4 DWORDS but not cache-line aligned. | |
| This cannot happen under Linux when scatter/gather lists are used since | |
| they only refer to system buffers that are well aligned. So, a work around | |
| may only be needed under Linux when a scatter/gather list is not used and | |
| when the SCSI DATA IN phase is reentered after a phase mismatch. | |
| 15. SCSI problem troubleshooting | |
| 15.1 Problem tracking | |
| Most SCSI problems are due to a non conformant SCSI bus or to buggy | |
| devices. If unfortunately you have SCSI problems, you can check the | |
| following things: | |
| - SCSI bus cables | |
| - terminations at both end of the SCSI chain | |
| - linux syslog messages (some of them may help you) | |
| If you do not find the source of problems, you can configure the | |
| driver with no features enabled. | |
| - only asynchronous data transfers | |
| - tagged commands disabled | |
| - disconnections not allowed | |
| Now, if your SCSI bus is ok, your system have every chance to work | |
| with this safe configuration but performances will not be optimal. | |
| If it still fails, then you can send your problem description to | |
| appropriate mailing lists or news-groups. Send me a copy in order to | |
| be sure I will receive it. Obviously, a bug in the driver code is | |
| possible. | |
| My email address: Gerard Roudier <[email protected]> | |
| Allowing disconnections is important if you use several devices on | |
| your SCSI bus but often causes problems with buggy devices. | |
| Synchronous data transfers increases throughput of fast devices like | |
| hard disks. Good SCSI hard disks with a large cache gain advantage of | |
| tagged commands queuing. | |
| Try to enable one feature at a time with control commands. For example: | |
| - echo "setsync all 25" >/proc/scsi/ncr53c8xx/0 | |
| Will enable fast synchronous data transfer negotiation for all targets. | |
| - echo "setflag 3" >/proc/scsi/ncr53c8xx/0 | |
| Will reset flags (no_disc) for target 3, and so will allow it to disconnect | |
| the SCSI Bus. | |
| - echo "settags 3 8" >/proc/scsi/ncr53c8xx/0 | |
| Will enable tagged command queuing for target 3 if that device supports it. | |
| Once you have found the device and the feature that cause problems, just | |
| disable that feature for that device. | |
| 15.2 Understanding hardware error reports | |
| When the driver detects an unexpected error condition, it may display a | |
| message of the following pattern. | |
| sym53c876-0:1: ERROR (0:48) (1-21-65) (f/95) @ (script 7c0:19000000). | |
| sym53c876-0: script cmd = 19000000 | |
| sym53c876-0: regdump: da 10 80 95 47 0f 01 07 75 01 81 21 80 01 09 00. | |
| Some fields in such a message may help you understand the cause of the | |
| problem, as follows: | |
| sym53c876-0:1: ERROR (0:48) (1-21-65) (f/95) @ (script 7c0:19000000). | |
| ............A.........B.C....D.E..F....G.H.......I.....J...K....... | |
| Field A : target number. | |
| SCSI ID of the device the controller was talking with at the moment the | |
| error occurs. | |
| Field B : DSTAT io register (DMA STATUS) | |
| Bit 0x40 : MDPE Master Data Parity Error | |
| Data parity error detected on the PCI BUS. | |
| Bit 0x20 : BF Bus Fault | |
| PCI bus fault condition detected | |
| Bit 0x01 : IID Illegal Instruction Detected | |
| Set by the chip when it detects an Illegal Instruction format | |
| on some condition that makes an instruction illegal. | |
| Bit 0x80 : DFE Dma Fifo Empty | |
| Pure status bit that does not indicate an error. | |
| If the reported DSTAT value contains a combination of MDPE (0x40), | |
| BF (0x20), then the cause may be likely due to a PCI BUS problem. | |
| Field C : SIST io register (SCSI Interrupt Status) | |
| Bit 0x08 : SGE SCSI GROSS ERROR | |
| Indicates that the chip detected a severe error condition | |
| on the SCSI BUS that prevents the SCSI protocol from functioning | |
| properly. | |
| Bit 0x04 : UDC Unexpected Disconnection | |
| Indicates that the device released the SCSI BUS when the chip | |
| was not expecting this to happen. A device may behave so to | |
| indicate the SCSI initiator that an error condition not reportable using the SCSI protocol has occurred. | |
| Bit 0x02 : RST SCSI BUS Reset | |
| Generally SCSI targets do not reset the SCSI BUS, although any | |
| device on the BUS can reset it at any time. | |
| Bit 0x01 : PAR Parity | |
| SCSI parity error detected. | |
| On a faulty SCSI BUS, any error condition among SGE (0x08), UDC (0x04) and | |
| PAR (0x01) may be detected by the chip. If your SCSI system sometimes | |
| encounters such error conditions, especially SCSI GROSS ERROR, then a SCSI | |
| BUS problem is likely the cause of these errors. | |
| For fields D,E,F,G and H, you may look into the sym53c8xx_defs.h file | |
| that contains some minimal comments on IO register bits. | |
| Field D : SOCL Scsi Output Control Latch | |
| This register reflects the state of the SCSI control lines the | |
| chip want to drive or compare against. | |
| Field E : SBCL Scsi Bus Control Lines | |
| Actual value of control lines on the SCSI BUS. | |
| Field F : SBDL Scsi Bus Data Lines | |
| Actual value of data lines on the SCSI BUS. | |
| Field G : SXFER SCSI Transfer | |
| Contains the setting of the Synchronous Period for output and | |
| the current Synchronous offset (offset 0 means asynchronous). | |
| Field H : SCNTL3 Scsi Control Register 3 | |
| Contains the setting of timing values for both asynchronous and | |
| synchronous data transfers. | |
| Understanding Fields I, J, K and dumps requires to have good knowledge of | |
| SCSI standards, chip cores functionnals and internal driver data structures. | |
| You are not required to decode and understand them, unless you want to help | |
| maintain the driver code. | |
| 16. Synchronous transfer negotiation tables | |
| Tables below have been created by calling the routine the driver uses | |
| for synchronisation negotiation timing calculation and chip setting. | |
| The first table corresponds to Ultra chips 53875 and 53C860 with 80 MHz | |
| clock and 5 clock divisors. | |
| The second one has been calculated by setting the scsi clock to 40 Mhz | |
| and using 4 clock divisors and so applies to all NCR53C8XX chips in fast | |
| SCSI-2 mode. | |
| Periods are in nano-seconds and speeds are in Mega-transfers per second. | |
| 1 Mega-transfers/second means 1 MB/s with 8 bits SCSI and 2 MB/s with | |
| Wide16 SCSI. | |
| 16.1 Synchronous timings for 53C895, 53C875 and 53C860 SCSI controllers | |
| ---------------------------------------------- | |
| Negotiated NCR settings | |
| Factor Period Speed Period Speed | |
| ------ ------ ------ ------ ------ | |
| 10 25 40.000 25 40.000 (53C895 only) | |
| 11 30.2 33.112 31.25 32.000 (53C895 only) | |
| 12 50 20.000 50 20.000 | |
| 13 52 19.230 62 16.000 | |
| 14 56 17.857 62 16.000 | |
| 15 60 16.666 62 16.000 | |
| 16 64 15.625 75 13.333 | |
| 17 68 14.705 75 13.333 | |
| 18 72 13.888 75 13.333 | |
| 19 76 13.157 87 11.428 | |
| 20 80 12.500 87 11.428 | |
| 21 84 11.904 87 11.428 | |
| 22 88 11.363 93 10.666 | |
| 23 92 10.869 93 10.666 | |
| 24 96 10.416 100 10.000 | |
| 25 100 10.000 100 10.000 | |
| 26 104 9.615 112 8.888 | |
| 27 108 9.259 112 8.888 | |
| 28 112 8.928 112 8.888 | |
| 29 116 8.620 125 8.000 | |
| 30 120 8.333 125 8.000 | |
| 31 124 8.064 125 8.000 | |
| 32 128 7.812 131 7.619 | |
| 33 132 7.575 150 6.666 | |
| 34 136 7.352 150 6.666 | |
| 35 140 7.142 150 6.666 | |
| 36 144 6.944 150 6.666 | |
| 37 148 6.756 150 6.666 | |
| 38 152 6.578 175 5.714 | |
| 39 156 6.410 175 5.714 | |
| 40 160 6.250 175 5.714 | |
| 41 164 6.097 175 5.714 | |
| 42 168 5.952 175 5.714 | |
| 43 172 5.813 175 5.714 | |
| 44 176 5.681 187 5.333 | |
| 45 180 5.555 187 5.333 | |
| 46 184 5.434 187 5.333 | |
| 47 188 5.319 200 5.000 | |
| 48 192 5.208 200 5.000 | |
| 49 196 5.102 200 5.000 | |
| 16.2 Synchronous timings for fast SCSI-2 53C8XX controllers | |
| ---------------------------------------------- | |
| Negotiated NCR settings | |
| Factor Period Speed Period Speed | |
| ------ ------ ------ ------ ------ | |
| 25 100 10.000 100 10.000 | |
| 26 104 9.615 125 8.000 | |
| 27 108 9.259 125 8.000 | |
| 28 112 8.928 125 8.000 | |
| 29 116 8.620 125 8.000 | |
| 30 120 8.333 125 8.000 | |
| 31 124 8.064 125 8.000 | |
| 32 128 7.812 131 7.619 | |
| 33 132 7.575 150 6.666 | |
| 34 136 7.352 150 6.666 | |
| 35 140 7.142 150 6.666 | |
| 36 144 6.944 150 6.666 | |
| 37 148 6.756 150 6.666 | |
| 38 152 6.578 175 5.714 | |
| 39 156 6.410 175 5.714 | |
| 40 160 6.250 175 5.714 | |
| 41 164 6.097 175 5.714 | |
| 42 168 5.952 175 5.714 | |
| 43 172 5.813 175 5.714 | |
| 44 176 5.681 187 5.333 | |
| 45 180 5.555 187 5.333 | |
| 46 184 5.434 187 5.333 | |
| 47 188 5.319 200 5.000 | |
| 48 192 5.208 200 5.000 | |
| 49 196 5.102 200 5.000 | |
| 17. Serial NVRAM (added by Richard Waltham: [email protected]) | |
| 17.1 Features | |
| Enabling serial NVRAM support enables detection of the serial NVRAM included | |
| on Symbios and some Symbios compatible host adaptors, and Tekram boards. The | |
| serial NVRAM is used by Symbios and Tekram to hold set up parameters for the | |
| host adaptor and its attached drives. | |
| The Symbios NVRAM also holds data on the boot order of host adaptors in a | |
| system with more than one host adaptor. This enables the order of scanning | |
| the cards for drives to be changed from the default used during host adaptor | |
| detection. | |
| This can be done to a limited extent at the moment using "reverse probe" but | |
| this only changes the order of detection of different types of cards. The | |
| NVRAM boot order settings can do this as well as change the order the same | |
| types of cards are scanned in, something "reverse probe" cannot do. | |
| Tekram boards using Symbios chips, DC390W/F/U, which have NVRAM are detected | |
| and this is used to distinguish between Symbios compatible and Tekram host | |
| adaptors. This is used to disable the Symbios compatible "diff" setting | |
| incorrectly set on Tekram boards if the CONFIG_SCSI_53C8XX_SYMBIOS_COMPAT | |
| configuration parameter is set enabling both Symbios and Tekram boards to be | |
| used together with the Symbios cards using all their features, including | |
| "diff" support. ("led pin" support for Symbios compatible cards can remain | |
| enabled when using Tekram cards. It does nothing useful for Tekram host | |
| adaptors but does not cause problems either.) | |
| 17.2 Symbios NVRAM layout | |
| typical data at NVRAM address 0x100 (53c810a NVRAM) | |
| ----------------------------------------------------------- | |
| 00 00 | |
| 64 01 | |
| 8e 0b | |
| 00 30 00 00 00 00 07 00 00 00 00 00 00 00 07 04 10 04 00 00 | |
| 04 00 0f 00 00 10 00 50 00 00 01 00 00 62 | |
| 04 00 03 00 00 10 00 58 00 00 01 00 00 63 | |
| 04 00 01 00 00 10 00 48 00 00 01 00 00 61 | |
| 00 00 00 00 00 00 00 00 00 00 00 00 00 00 | |
| 0f 00 08 08 64 00 0a 00 | |
| 0f 00 08 08 64 00 0a 00 | |
| 0f 00 08 08 64 00 0a 00 | |
| 0f 00 08 08 64 00 0a 00 | |
| 0f 00 08 08 64 00 0a 00 | |
| 0f 00 08 08 64 00 0a 00 | |
| 0f 00 08 08 64 00 0a 00 | |
| 0f 00 08 08 64 00 0a 00 | |
| 0f 00 08 08 64 00 0a 00 | |
| 0f 00 08 08 64 00 0a 00 | |
| 0f 00 08 08 64 00 0a 00 | |
| 0f 00 08 08 64 00 0a 00 | |
| 0f 00 08 08 64 00 0a 00 | |
| 0f 00 08 08 64 00 0a 00 | |
| 0f 00 08 08 64 00 0a 00 | |
| 0f 00 08 08 64 00 0a 00 | |
| 00 00 00 00 00 00 00 00 | |
| 00 00 00 00 00 00 00 00 | |
| 00 00 00 00 00 00 00 00 | |
| 00 00 00 00 00 00 00 00 | |
| 00 00 00 00 00 00 00 00 | |
| 00 00 00 00 00 00 00 00 | |
| 00 00 00 00 00 00 00 00 | |
| 00 00 00 00 00 00 00 00 | |
| 00 00 00 00 00 00 00 00 | |
| 00 00 00 00 00 00 00 00 | |
| 00 00 00 00 00 00 00 00 | |
| 00 00 00 00 00 00 00 00 | |
| 00 00 00 00 00 00 00 00 | |
| 00 00 00 00 00 00 00 00 | |
| 00 00 00 00 00 00 00 00 | |
| 00 00 00 00 00 00 00 00 | |
| 00 00 00 00 00 00 00 00 | |
| 00 00 00 00 00 00 00 00 | |
| 00 00 00 00 00 00 00 00 | |
| fe fe | |
| 00 00 | |
| 00 00 | |
| ----------------------------------------------------------- | |
| NVRAM layout details | |
| NVRAM Address 0x000-0x0ff not used | |
| 0x100-0x26f initialised data | |
| 0x270-0x7ff not used | |
| general layout | |
| header - 6 bytes, | |
| data - 356 bytes (checksum is byte sum of this data) | |
| trailer - 6 bytes | |
| --- | |
| total 368 bytes | |
| data area layout | |
| controller set up - 20 bytes | |
| boot configuration - 56 bytes (4x14 bytes) | |
| device set up - 128 bytes (16x8 bytes) | |
| unused (spare?) - 152 bytes (19x8 bytes) | |
| --- | |
| total 356 bytes | |
| ----------------------------------------------------------- | |
| header | |
| 00 00 - ?? start marker | |
| 64 01 - byte count (lsb/msb excludes header/trailer) | |
| 8e 0b - checksum (lsb/msb excludes header/trailer) | |
| ----------------------------------------------------------- | |
| controller set up | |
| 00 30 00 00 00 00 07 00 00 00 00 00 00 00 07 04 10 04 00 00 | |
| | | | | | |
| | | | -- host ID | |
| | | | | |
| | | --Removable Media Support | |
| | | 0x00 = none | |
| | | 0x01 = Bootable Device | |
| | | 0x02 = All with Media | |
| | | | |
| | --flag bits 2 | |
| | 0x00000001= scan order hi->low | |
| | (default 0x00 - scan low->hi) | |
| --flag bits 1 | |
| 0x00000001 scam enable | |
| 0x00000010 parity enable | |
| 0x00000100 verbose boot msgs | |
| remaining bytes unknown - they do not appear to change in my | |
| current set up for any of the controllers. | |
| default set up is identical for 53c810a and 53c875 NVRAM | |
| (Removable Media added Symbios BIOS version 4.09) | |
| ----------------------------------------------------------- | |
| boot configuration | |
| boot order set by order of the devices in this table | |
| 04 00 0f 00 00 10 00 50 00 00 01 00 00 62 -- 1st controller | |
| 04 00 03 00 00 10 00 58 00 00 01 00 00 63 2nd controller | |
| 04 00 01 00 00 10 00 48 00 00 01 00 00 61 3rd controller | |
| 00 00 00 00 00 00 00 00 00 00 00 00 00 00 4th controller | |
| | | | | | | | | | |
| | | | | | | ---- PCI io port adr | |
| | | | | | --0x01 init/scan at boot time | |
| | | | | --PCI device/function number (0xdddddfff) | |
| | | ----- ?? PCI vendor ID (lsb/msb) | |
| ----PCI device ID (lsb/msb) | |
| ?? use of this data is a guess but seems reasonable | |
| remaining bytes unknown - they do not appear to change in my | |
| current set up | |
| default set up is identical for 53c810a and 53c875 NVRAM | |
| ----------------------------------------------------------- | |
| device set up (up to 16 devices - includes controller) | |
| 0f 00 08 08 64 00 0a 00 - id 0 | |
| 0f 00 08 08 64 00 0a 00 | |
| 0f 00 08 08 64 00 0a 00 | |
| 0f 00 08 08 64 00 0a 00 | |
| 0f 00 08 08 64 00 0a 00 | |
| 0f 00 08 08 64 00 0a 00 | |
| 0f 00 08 08 64 00 0a 00 | |
| 0f 00 08 08 64 00 0a 00 | |
| 0f 00 08 08 64 00 0a 00 | |
| 0f 00 08 08 64 00 0a 00 | |
| 0f 00 08 08 64 00 0a 00 | |
| 0f 00 08 08 64 00 0a 00 | |
| 0f 00 08 08 64 00 0a 00 | |
| 0f 00 08 08 64 00 0a 00 | |
| 0f 00 08 08 64 00 0a 00 | |
| 0f 00 08 08 64 00 0a 00 - id 15 | |
| | | | | | | | |
| | | | | ----timeout (lsb/msb) | |
| | | | --synch period (0x?? 40 Mtrans/sec- fast 40) (probably 0x28) | |
| | | | (0x30 20 Mtrans/sec- fast 20) | |
| | | | (0x64 10 Mtrans/sec- fast ) | |
| | | | (0xc8 5 Mtrans/sec) | |
| | | | (0x00 asynchronous) | |
| | | -- ?? max sync offset (0x08 in NVRAM on 53c810a) | |
| | | (0x10 in NVRAM on 53c875) | |
| | --device bus width (0x08 narrow) | |
| | (0x10 16 bit wide) | |
| --flag bits | |
| 0x00000001 - disconnect enabled | |
| 0x00000010 - scan at boot time | |
| 0x00000100 - scan luns | |
| 0x00001000 - queue tags enabled | |
| remaining bytes unknown - they do not appear to change in my | |
| current set up | |
| ?? use of this data is a guess but seems reasonable | |
| (but it could be max bus width) | |
| default set up for 53c810a NVRAM | |
| default set up for 53c875 NVRAM - bus width - 0x10 | |
| - sync offset ? - 0x10 | |
| - sync period - 0x30 | |
| ----------------------------------------------------------- | |
| ?? spare device space (32 bit bus ??) | |
| 00 00 00 00 00 00 00 00 (19x8bytes) | |
| . | |
| . | |
| 00 00 00 00 00 00 00 00 | |
| default set up is identical for 53c810a and 53c875 NVRAM | |
| ----------------------------------------------------------- | |
| trailer | |
| fe fe - ? end marker ? | |
| 00 00 | |
| 00 00 | |
| default set up is identical for 53c810a and 53c875 NVRAM | |
| ----------------------------------------------------------- | |
| 17.3 Tekram NVRAM layout | |
| nvram 64x16 (1024 bit) | |
| Drive settings | |
| Drive ID 0-15 (addr 0x0yyyy0 = device setup, yyyy = ID) | |
| (addr 0x0yyyy1 = 0x0000) | |
| x x x x x x x x x x x x x x x x | |
| | | | | | | | | | | |
| | | | | | | | | ----- parity check 0 - off | |
| | | | | | | | | 1 - on | |
| | | | | | | | | | |
| | | | | | | | ------- sync neg 0 - off | |
| | | | | | | | 1 - on | |
| | | | | | | | | |
| | | | | | | --------- disconnect 0 - off | |
| | | | | | | 1 - on | |
| | | | | | | | |
| | | | | | ----------- start cmd 0 - off | |
| | | | | | 1 - on | |
| | | | | | | |
| | | | | -------------- tagged cmds 0 - off | |
| | | | | 1 - on | |
| | | | | | |
| | | | ---------------- wide neg 0 - off | |
| | | | 1 - on | |
| | | | | |
| --------------------------- sync rate 0 - 10.0 Mtrans/sec | |
| 1 - 8.0 | |
| 2 - 6.6 | |
| 3 - 5.7 | |
| 4 - 5.0 | |
| 5 - 4.0 | |
| 6 - 3.0 | |
| 7 - 2.0 | |
| 7 - 2.0 | |
| 8 - 20.0 | |
| 9 - 16.7 | |
| a - 13.9 | |
| b - 11.9 | |
| Global settings | |
| Host flags 0 (addr 0x100000, 32) | |
| x x x x x x x x x x x x x x x x | |
| | | | | | | | | | | | | | |
| | | | | | | | | ----------- host ID 0x00 - 0x0f | |
| | | | | | | | | | |
| | | | | | | | ----------------------- support for 0 - off | |
| | | | | | | | > 2 drives 1 - on | |
| | | | | | | | | |
| | | | | | | ------------------------- support drives 0 - off | |
| | | | | | | > 1Gbytes 1 - on | |
| | | | | | | | |
| | | | | | --------------------------- bus reset on 0 - off | |
| | | | | | power on 1 - on | |
| | | | | | | |
| | | | | ----------------------------- active neg 0 - off | |
| | | | | 1 - on | |
| | | | | | |
| | | | -------------------------------- imm seek 0 - off | |
| | | | 1 - on | |
| | | | | |
| | | ---------------------------------- scan luns 0 - off | |
| | | 1 - on | |
| | | | |
| -------------------------------------- removable 0 - disable | |
| as BIOS dev 1 - boot device | |
| 2 - all | |
| Host flags 1 (addr 0x100001, 33) | |
| x x x x x x x x x x x x x x x x | |
| | | | | | | | |
| | | | --------- boot delay 0 - 3 sec | |
| | | | 1 - 5 | |
| | | | 2 - 10 | |
| | | | 3 - 20 | |
| | | | 4 - 30 | |
| | | | 5 - 60 | |
| | | | 6 - 120 | |
| | | | | |
| --------------------------- max tag cmds 0 - 2 | |
| 1 - 4 | |
| 2 - 8 | |
| 3 - 16 | |
| 4 - 32 | |
| Host flags 2 (addr 0x100010, 34) | |
| x x x x x x x x x x x x x x x x | |
| | | |
| ----- F2/F6 enable 0 - off ??? | |
| 1 - on ??? | |
| checksum (addr 0x111111) | |
| checksum = 0x1234 - (sum addr 0-63) | |
| ---------------------------------------------------------------------------- | |
| default nvram data: | |
| 0x0037 0x0000 0x0037 0x0000 0x0037 0x0000 0x0037 0x0000 | |
| 0x0037 0x0000 0x0037 0x0000 0x0037 0x0000 0x0037 0x0000 | |
| 0x0037 0x0000 0x0037 0x0000 0x0037 0x0000 0x0037 0x0000 | |
| 0x0037 0x0000 0x0037 0x0000 0x0037 0x0000 0x0037 0x0000 | |
| 0x0f07 0x0400 0x0001 0x0000 0x0000 0x0000 0x0000 0x0000 | |
| 0x0000 0x0000 0x0000 0x0000 0x0000 0x0000 0x0000 0x0000 | |
| 0x0000 0x0000 0x0000 0x0000 0x0000 0x0000 0x0000 0x0000 | |
| 0x0000 0x0000 0x0000 0x0000 0x0000 0x0000 0x0000 0xfbbc | |
| 18. Support for Big Endian | |
| The PCI local bus has been primarily designed for x86 architecture. | |
| As a consequence, PCI devices generally expect DWORDS using little endian | |
| byte ordering. | |
| 18.1 Big Endian CPU | |
| In order to support NCR chips on a Big Endian architecture the driver has to | |
| perform byte reordering each time it is needed. This feature has been | |
| added to the driver by Cort <[email protected]> and is available in driver | |
| version 2.5 and later ones. For the moment Big Endian support has only | |
| been tested on Linux/PPC (PowerPC). | |
| 18.2 NCR chip in Big Endian mode of operations | |
| It can be read in SYMBIOS documentation that some chips support a special | |
| Big Endian mode, on paper: 53C815, 53C825A, 53C875, 53C875N, 53C895. | |
| This mode of operations is not software-selectable, but needs pin named | |
| BigLit to be pulled-up. Using this mode, most of byte reorderings should | |
| be avoided when the driver is running on a Big Endian CPU. | |
| Driver version 2.5 is also, in theory, ready for this feature. | |
| =============================================================================== | |
| End of NCR53C8XX driver README file |