linux-kernel - RE: [PATCH 2/2] usb: musb: Stop bulk endpoint while queue is rotated

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Message-ID: <7a4fb42ac94140d7a5d34eb1c0b5934b@THHSTE15D2BE2.hs20.net>
Date:	Fri, 20 May 2016 17:06:33 +0000
From:	Andrew Goodbody <andrew.goodbody@...brionix.com>
To:	Sergei Shtylyov <sergei.shtylyov@...entembedded.com>,
	"b-liu@...com" <b-liu@...com>
CC:	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: RE: [PATCH 2/2] usb: musb: Stop bulk endpoint while queue is rotated

> From: Sergei Shtylyov [mailto:sergei.shtylyov@...entembedded.com]
> On 05/20/2016 05:51 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@...brionix.com>
> > Cc: stable@...r.kernel.org
> > ---
> >  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.

Andrew

> [...]
> 
> MBR, Sergei