linux-kernel - [PATCH 3.16 178/305] usb: musb: Stop bulk endpoint while queue is rotated

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Message-ID: <lsq.1471110171.476937233@decadent.org.uk>
Date:	Sat, 13 Aug 2016 18:42:51 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org, "Bin Liu" <b-liu@...com>,
	"Greg Kroah-Hartman" <gregkh@...uxfoundation.org>,
	"Andrew Goodbody" <andrew.goodbody@...brionix.com>
Subject: [PATCH 3.16 178/305] usb: musb: Stop bulk endpoint while queue is
 rotated

3.16.37-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Andrew Goodbody <andrew.goodbody@...brionix.com>

commit 7b2c17f829545df27a910e8d82e133c21c9a8c9c upstream.

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>
Signed-off-by: Bin Liu <b-liu@...com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/usb/musb/musb_host.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

--- a/drivers/usb/musb/musb_host.c
+++ b/drivers/usb/musb/musb_host.c
@@ -949,9 +949,15 @@ static void musb_bulk_nak_timeout(struct
 	if (is_in) {
 		dma = is_dma_capable() ? ep->rx_channel : NULL;
 
-		/* clear nak timeout bit */
+		/*
+		 * Need to stop the transaction by clearing REQPKT first
+		 * then the NAK Timeout bit ref MUSBMHDRC USB 2.0 HIGH-SPEED
+		 * DUAL-ROLE CONTROLLER Programmer's Guide, section 9.2.2
+		 */
 		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);