From: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> 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@xxxxxxxxxxxxxxxxxxx> CC: Matthew Dharm <mdharm-usb@xxxxxxxxxxxxxxxxxx> Acked-by: Jens Axboe <jens.axboe@xxxxxxxxxx> Tested-by: Thomas Hommel <Thomas.Hommel@xxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx> --- drivers/usb/storage/scsiglue.c | 8 ++++++++ 1 files changed, 8 insertions(+), 0 deletions(-) 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 @@ 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. */ -- 1.6.0.4 -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
