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

[Sergei Shtylyov]

On 05/20/2016 08:06 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
> > > ---
> > >  drivers/usb/musb/musb_host.c | 2 ++
> > >  1 file changed, 2 insertions(+)
> > >
> > > diff --git a/drivers/usb/musb/musb_host.c
> > > b/drivers/usb/musb/musb_host.c index 30e0d65..777ff30 100644
> > > --- a/drivers/usb/musb/musb_host.c
> > > +++ b/drivers/usb/musb/musb_host.c
> > > @@ -999,6 +999,8 @@ 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;
> > > +		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);
> >
> >     Can we not clear both in one write?
>
> Section 16.3.8.2.2.1.2 of the TRM says to clear REQPKT before DATAERR_NAKTIMEOUT.

   Right, the MUSB programmer's guide also says that. Then a comment wouldn't 
hurt here.

> Andrew

MBR, Sergei