On Thu, 20 Nov 2008, FUJITA Tomonori wrote:

quoted text
> We have been used 4GB for long time if dma_mask is zero (I guess we
> use 4GB as kinda the default dma address limit at several places). The
> majority of drivers (such as pci) sets properly dev->dma_mask so the
> patch might not change anything but suddenly changing the
> long-standing rule in an odd way (use BLK_BOUNCE_HIGH if dma_mask is
> zero) doesn't sound a good idea to me.
> 
> Why not calling blk_queue_bounce_limit() in the slave_configure hook?
> I think that it's the common way for SCSI LLDs with odd bounce limit.

Thomas, here's a patch to do what Tomonori suggests.  Try replacing the 
old patch with this one.

Alan Stern


Index: usb-2.6/drivers/usb/storage/scsiglue.c
===================================================================
--- usb-2.6.orig/drivers/usb/storage/scsiglue.c
+++ usb-2.6/drivers/usb/storage/scsiglue.c
@@ -129,6 +129,14 @@ static int slave_configure(struct scsi_d
 					      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. */

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