linux-kernel - [PATCH 3.12 106/123] usb: musb: fix cppi channel teardown for isoch transfer

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Message-Id: <bc824592296953d0ab39e657a9f17886575f131e.1446021555.git.jslaby@suse.cz>
Date:	Wed, 28 Oct 2015 14:53:37 +0100
From:	Jiri Slaby <jslaby@...e.cz>
To:	stable@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, Bin Liu <b-liu@...com>,
	Felipe Balbi <balbi@...com>, Oliver Neukum <ONeukum@...e.com>,
	Jiri Slaby <jslaby@...e.cz>
Subject: [PATCH 3.12 106/123] usb: musb: fix cppi channel teardown for isoch transfer

From: Bin Liu <b-liu@...com>

3.12-stable review patch.  If anyone has any objections, please let me know.

===============

commit b431ba8803666e56c1d178a421b3cbc36e8d3d33 upstream.

After a few iterations of start/stop UVC camera streaming, the streaming
stops.

This patch adds 250us delay in the cppi channel abort path to let cppi
drain properly.

Using 50us delay seems to be too aggressive, some webcams are still
broken. 250us is the original value used in TI 3.2 kernel.

Signed-off-by: Bin Liu <b-liu@...com>
Signed-off-by: Felipe Balbi <balbi@...com>
Cc: Oliver Neukum <ONeukum@...e.com>
Signed-off-by: Jiri Slaby <jslaby@...e.cz>
---
 drivers/usb/musb/musb_cppi41.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/usb/musb/musb_cppi41.c b/drivers/usb/musb/musb_cppi41.c
index 1c9c626248fd..2ed1695ff5ad 100644
--- a/drivers/usb/musb/musb_cppi41.c
+++ b/drivers/usb/musb/musb_cppi41.c
@@ -509,6 +509,9 @@ static int cppi41_dma_channel_abort(struct dma_channel *channel)
 	} else {
 		cppi41_set_autoreq_mode(cppi41_channel, EP_MODE_AUTOREQ_NONE);
 
+		/* delay to drain to cppi dma pipeline for isoch */
+		udelay(250);
+
 		csr = musb_readw(epio, MUSB_RXCSR);
 		csr &= ~(MUSB_RXCSR_H_REQPKT | MUSB_RXCSR_DMAENAB);
 		musb_writew(epio, MUSB_RXCSR, csr);
-- 
2.6.2

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