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

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Message-ID: <1464004844-26553-3-git-send-email-andrew.goodbody@cambrionix.com>
Date:	Mon, 23 May 2016 13:00:44 +0100
From:	Andrew Goodbody <andrew.goodbody@...brionix.com>
To:	<b-liu@...com>
CC:	<gregkh@...uxfoundation.org>, <linux-usb@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>,
	Andrew Goodbody <andrew.goodbody@...brionix.com>,
	<stable@...r.kernel.org>
Subject: [PATCH V2 2/2] usb: musb: Stop bulk endpoint while queue is rotated

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
---
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
+		 * DATAERR_NAKTIMEOUT ref TRM section 16.3.8.2.2.1.2
+		 */
+		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);
 
-- 
2.7.4