Re: [PATCH V2 2/2] usb: musb: Stop bulk endpoint while queue is rotated

[Sergei Shtylyov]

On 05/23/2016 06:19 PM, Andrew Goodbody wrote:

> > > > > > Ensure that the endpoint is stopped by clearing REQPKT before
> > > > > > clearing DATAERR_NAKTIMEOUT before rotating the queue on the
> > > > > > dedicated bulk endpoint.
> > > > > > This addresses an issue where a race could result in the endpoint
> > > > > > receiving data before it was reprogrammed resulting in a warning
> > > > > > about such data from musb_rx_reinit before it was thrown away.
> > > > > > The data thrown away was a valid packet that had been correctly
> > > > > > ACKed which meant the host and device got out of sync.
> > > > > >
> > > > > > Signed-off-by: Andrew Goodbody
> > <andrew.goodbody@xxxxxxxxxxxxxx>
> > > > > > Cc: stable@xxxxxxxxxxxxxxx
> > > > > > ---
> > > > > > V2 added comment about clearing REQPKT before
> > DATAERR_NAKTIMEOUT
> > > > > >  drivers/usb/musb/musb_host.c | 6 ++++++
> > > > > >  1 file changed, 6 insertions(+)
> > > > > >
> > > > > > diff --git a/drivers/usb/musb/musb_host.c
> > > > > > b/drivers/usb/musb/musb_host.c index 2966596..676cb98 100644
> > > > > > --- a/drivers/usb/musb/musb_host.c
> > > > > > +++ b/drivers/usb/musb/musb_host.c
> > > > > > @@ -997,6 +997,12 @@ static void musb_bulk_nak_timeout(struct
> > musb
> > > > > *musb, struct musb_hw_ep *ep,
> > > > > >          /* clear nak timeout bit */
> > > > > >          rx_csr = musb_readw(epio, MUSB_RXCSR);
> > > > > >          rx_csr |= MUSB_RXCSR_H_WZC_BITS;
> > > > > > +        /*
> > > > > > +         * Need to stop the transaction by clearing REQPKT before
> > > > >
> > > > >     Transcation? Maybe transfer?
> > > >
> > > > The quote from the TRM is "If the DATAERR_NAKTIMEOUT bit is set, the
> > > > controller can be directed either to continue trying this transaction
> > > > (until it times out again) by clearing the DATAERR_NAKTIMEOUT bit or
> > > > to abort the transaction by clearing REQPKT bit before clearing the
> > DATAERR_NAKTIMEOUT bit."
> > > > So 'transaction' is correct.
> > >
> > >    OK.
> > >
> > > > > > +         * DATAERR_NAKTIMEOUT ref TRM section 16.3.8.2.2.1.2
> > > > >
> > > > >     Which TRM? Do you understand that the MUSB core is used by
> > > > > multiple SoCs?
> > > > > I'd recommend referring just to the "abstract" manual or the MUSB
> > > > > programmer's guide (section 9.2.2 if you want an exact ref.).
> > >
> > > > That would be the AM335x Sitara Processors TRM. I don't have the MUSB
> > > > programmer's guide, is it available online somewhere?
> > >
> > >    AFAIK, no.
> > >
> > > > I do not understand what you mean by the "abstract" manual.
> > >
> > >    Just saying "the manual" or "the manuals".
> > >
> > > > Would you be OK with "ref MUSB Programmer's Guide section 9.2.2"
> > >
> > >    Yes.
> >
> >     The full document name is "MUSBMHDRC USB 2.0 HIGH-SPEED DUAL-ROLE
> > CONTROLLER Programmer's Guide".
>
> I moved the comment up to replace the one at the top so the patch now looks like this
>
> 	if (is_in) {
>  		dma = is_dma_capable() ? ep->rx_channel : NULL;
>
> -		/* clear nak timeout bit */
> +		/*
> +		 * Need to stop the transaction by clearing REQPKT first
> +		 * then the NAK Timeout bit ref MUSBMHDRC USB 2.0 HIGH-SPEED
> +		 * DUAL-ROLE CONTROLLER Programmer's Guide, section 9.2.2
> +		 */
>  		rx_csr = musb_readw(epio, MUSB_RXCSR);
>  		rx_csr |= MUSB_RXCSR_H_WZC_BITS;
> +		rx_csr &= ~MUSB_RXCSR_H_REQPKT;
> +		musb_writew(epio, MUSB_RXCSR, rx_csr);
>  		rx_csr &= ~MUSB_RXCSR_DATAERROR;
>  		musb_writew(epio, MUSB_RXCSR, rx_csr);
>
>
> Are you OK with that now?
> Andrew

   Yes, thank you.

MBR, Sergei