Re: [PATCH] usb: host: xhci-plat: Enable XHCI_SPURIOUS_SUCCESS quirkfor xhci-plat

[George Cherian]

On 6/26/2013 2:32 PM, Felipe Balbi wrote:
> Hi,
>
> On Wed, Jun 26, 2013 at 02:28:57PM +0530, George Cherian wrote:
> > Synopsis xhci controllers with hci_version > 0.96 gives spurious success
> > events on short packet completion. During webcam capture the
> > "ERROR Transfer event TRB DMA ptr not part of current TD" was observed.
> > The same application works fine with synopsis controllers hci_version 0.96.
> >
> > Signed-off-by: George Cherian<george.cherian@xxxxxx>
> > ---
> >   drivers/usb/host/xhci-plat.c | 10 ++++++++++
> >   1 file changed, 10 insertions(+)
> >
> > diff --git a/drivers/usb/host/xhci-plat.c b/drivers/usb/host/xhci-plat.c
> > index 93ad67e..e63c6d3 100644
> > --- a/drivers/usb/host/xhci-plat.c
> > +++ b/drivers/usb/host/xhci-plat.c
> > @@ -25,6 +25,16 @@ static void xhci_plat_quirks(struct device *dev, struct xhci_hcd *xhci)
> >   	 * dev struct in order to setup MSI
> >   	 */
> >   	xhci->quirks |= XHCI_BROKEN_MSI;
> > +
> > +	/*
> > +	 * In some xhci controllers which follows xhci 1.0 spec gives a spurious
> > +	 * success event after a short transfer. This quirk will ignore such
> > +	 * spurious event. Hit this issue in synopsis xhci controllers with
> > +	 * hci_version > 0.96
> > +	 */
> > +
> > +	if (xhci->hci_version > 0x96)
> > +		xhci->quirks |= XHCI_SPURIOUS_SUCCESS;
> >   }
> doesn't look like the correct way to do this. What if enabling that
> quirk on hosts which don't have the quirk cause problems ?
For a controller which does not have this issue will never get a 
spurious success for short packet ( and that too for only ISOCH).

per this commit ad808333d Intel xhci: Ignore spurious successful event.

This spurious successful event behavior isn't technically disallowed by
the xHCI specification, so make the xHCI driver just ignore the spurious
completion event.
> I would suggest adding a platform_data which (in our case) dwc3 will
> pass to xhci-plat. Then you can do proper revision detection of the
> synopsys controller and set the quirk only on the failing hosts.
>
> BTW, do you have the STARS number for this errata ?
No STARS number yet.


Regards
-George
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