Merge pull request #50 from MaxKrummenacher/4.14-2.0.x-imx

4.14 2.0.x imx

1 files changed, 12 insertions, 14 deletions

diff --git a/drivers/usb/storage/scsiglue.c b/drivers/usb/storage/scsiglue.c
index 13f2c051dbf2..afb4b0bf47b3 100644
--- a/drivers/usb/storage/scsiglue.c
+++ b/drivers/usb/storage/scsiglue.c
@@ -81,6 +81,7 @@ static const char* host_info(struct Scsi_Host *host)
 static int slave_alloc (struct scsi_device *sdev)
 {
 	struct us_data *us = host_to_us(sdev->host);
+	int maxp;
 
 	/*
 	 * Set the INQUIRY transfer length to 36.  We don't use any of
@@ -90,20 +91,17 @@ static int slave_alloc (struct scsi_device *sdev)
 	sdev->inquiry_len = 36;
 
 	/*
-	 * USB has unusual DMA-alignment requirements: Although the
-	 * starting address of each scatter-gather element doesn't matter,
-	 * the length of each element except the last must be divisible
-	 * by the Bulk maxpacket value.  There's currently no way to
-	 * express this by block-layer constraints, so we'll cop out
-	 * and simply require addresses to be aligned at 512-byte
-	 * boundaries.  This is okay since most block I/O involves
-	 * hardware sectors that are multiples of 512 bytes in length,
-	 * and since host controllers up through USB 2.0 have maxpacket
-	 * values no larger than 512.
-	 *
-	 * But it doesn't suffice for Wireless USB, where Bulk maxpacket
-	 * values can be as large as 2048.  To make that work properly
-	 * will require changes to the block layer.
+	 * USB has unusual scatter-gather requirements: the length of each
+	 * scatterlist element except the last must be divisible by the
+	 * Bulk maxpacket value.  Fortunately this value is always a
+	 * power of 2.  Inform the block layer about this requirement.
+	 */
+	maxp = usb_maxpacket(us->pusb_dev, us->recv_bulk_pipe, 0);
+	blk_queue_virt_boundary(sdev->request_queue, maxp - 1);
+
+	/*
+	 * Some host controllers may have alignment requirements.
+	 * We'll play it safe by requiring 512-byte alignment always.
 	 */
 	blk_queue_update_dma_alignment(sdev->request_queue, (512 - 1));