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Date: Mon, 21 Dec 2015 15:25:05 +0300 From: Sergei Shtylyov <sergei.shtylyov@...entembedded.com> To: Vikas Bansal <vikas.bansal@...sung.com>, mathias.nyman@...el.com, gregkh@...uxfoundation.org, linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org Cc: sumit.batra@...sung.com Subject: Re: [PATCH] BugFix in XHCI controller driver for scatter gather DMA Hello. On 12/21/2015 3:15 PM, Vikas Bansal wrote: > From: Sumit Batra <sumit.batra@...sung.com> > > 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@...sung.com> > Signed-off-by: Vikas Bansal <vikas.bansal@...sung.com> > 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-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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