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 <stern@rowland.harvard.edu>
CC: Matthew Dharm <mdharm-usb@one-eyed-alien.net>
Acked-by: Jens Axboe <jens.axboe@oracle.com>
Tested-by: Thomas Hommel <Thomas.Hommel@gefanuc.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 8 insertions, 0 deletions

diff --git a/drivers/usb/storage/scsiglue.c b/drivers/usb/storage/scsiglue.c
index 1b35e011a34f..e9d6c196a7ab 100644
--- a/drivers/usb/storage/scsiglue.c
+++ b/drivers/usb/storage/scsiglue.c
@@ -129,6 +129,14 @@ static int slave_configure(struct scsi_device *sdev)
                                               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. */