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

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Date:	Fri, 20 May 2016 19:21:12 +0300
From:	Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
To:	Andrew Goodbody <andrew.goodbody@...brionix.com>, b-liu@...com
Cc:	gregkh@...uxfoundation.org, linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH 2/2] usb: musb: Stop bulk endpoint while queue is rotated

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?

[...]

MBR, Sergei