From: Sumit Batra <[email protected]>
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 <[email protected]>
Signed-off-by: Vikas Bansal <[email protected]>
diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index 7d34cbf..7363dee 100644
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -3110,7 +3110,9 @@ 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)
+ field |= TRB_CHAIN;
} else {
/* FIXME - add check for ZERO_PACKET flag before this */
td->last_trb = ep_ring->enqueue;
Hello.
On 12/21/2015 03:46 PM, Vikas Bansal wrote:
> From: Sumit Batra <[email protected]>
>
> 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 <[email protected]>
> Signed-off-by: Vikas Bansal <[email protected]>
> diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
> index 7d34cbf..7363dee 100644
> --- a/drivers/usb/host/xhci-ring.c
> +++ b/drivers/usb/host/xhci-ring.c
> @@ -3110,7 +3110,9 @@ 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)
Indent with 2 extra tabs ISO 1 please -- it'll be easier on the eyes
(blends with the next statement otherwise).
> + field |= TRB_CHAIN;
> } else {
> /* FIXME - add check for ZERO_PACKET flag before this */
> td->last_trb = ep_ring->enqueue;
MBR, Sergei