Hello.
On 12/21/2015 3:15 PM, Vikas Bansal wrote:
From: Sumit Batra <sumit.batra@xxxxxxxxxxx>
Pre-Condition
URB with Scatter Gather list is queued to bulk OUT endpoint.
Every buffer in scatter gather list is not a multiple of maximum packet size for that endpoint(short packet).
CHAIN bit is set for all TRBs in a TD so that the DMA happens to all of them at once.
Issue
DMA operation copies all the CHAINED TRBs at contiguous device memory.
But since the original packet was a short packet, so the actual data is re-aligned after this DMA operation.
At device end this re-aligned data causes data integrity issue with applications like ICMP ping.
Solution
Don't set the CHAINED bit for these TRBs, if their buffers are not a multiple of maximum packet size.
This will reduce the benefit in throughput as required from a scatter gather implementation, but this reduces the CPU utilization.
And solves the data integrity issue on Device End
Signed-off-by: Sumit Batra <sumit.batra@xxxxxxxxxxx>
Signed-off-by: Vikas Bansal <vikas.bansal@xxxxxxxxxxx>
diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index 7d34cbf..862d7cd 100644
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -3110,7 +3110,8 @@ static int queue_bulk_sg_tx(struct xhci_hcd *xhci, gfp_t mem_flags,
* TRB to indicate it's the last TRB in the chain.
*/
if (num_trbs > 1) {
- field |= TRB_CHAIN;
+ if(this_sg_len % usb_endpoint_maxp(&urb->ep->desc) == 0)
Space needed after *if*. Please run your patches thru scripts/checkpatch.pl.
[...]
MBR, Sergei
--
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
