USB: storage: set bounce limit for non-DMA-capable host controllers
This patch (as1175) makes usb-storage set a SCSI device's
request-queue bounce limit such that all buffers will be located in
addressable memory (i.e., not in high memory) if the host controller's
dma_mask is NULL. This is necessary when the host controller doesn't
support DMA: If a buffer is in high memory then the both the virtual
and DMA addresses produced by the scatter-gather library will be NULL,
preventing the HCD from accessing the buffer's data.
In particular, the isp1760 driver needs this when used on a system
with more than 1 GB of memory.
Signed-off-by: Alan Stern <[email protected]>
CC: Matthew Dharm <[email protected]>
Acked-by: Jens Axboe <[email protected]>
Tested-by: Thomas Hommel <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
diff --git a/drivers/usb/storage/scsiglue.c b/drivers/usb/storage/scsiglue.c
index 1b35e01..e9d6c19 100644
--- a/drivers/usb/storage/scsiglue.c
+++ b/drivers/usb/storage/scsiglue.c
@@ -129,6 +129,14 @@
max_sectors);
}
+ /* Some USB host controllers can't do DMA; they have to use PIO.
+ * They indicate this by setting their dma_mask to NULL. For
+ * such controllers we need to make sure the block layer sets
+ * up bounce buffers in addressable memory.
+ */
+ if (!us->pusb_dev->bus->controller->dma_mask)
+ blk_queue_bounce_limit(sdev->request_queue, BLK_BOUNCE_HIGH);
+
/* We can't put these settings in slave_alloc() because that gets
* called before the device type is known. Consequently these
* settings can't be overridden via the scsi devinfo mechanism. */
