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

[Sergei Shtylyov]

On 05/23/2016 04:40 PM, Sergei Shtylyov 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".

> > Andrew
> >
> > > [...]

MBR, Sergei