linux-kernel - [PATCH AUTOSEL 4.4 09/30] media: mt9p031: Fix corrupted frame after restarting stream

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Message-Id: <20211109010918.1192063-9-sashal@kernel.org>
Date:   Mon,  8 Nov 2021 20:08:57 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Dirk Bender <d.bender@...tec.de>,
        Stefan Riedmueller <s.riedmueller@...tec.de>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Mauro Carvalho Chehab <mchehab+huawei@...nel.org>,
        Sasha Levin <sashal@...nel.org>,
        laurent.pinchart@...asonboard.com, mchehab@...nel.org,
        linux-media@...r.kernel.org
Subject: [PATCH AUTOSEL 4.4 09/30] media: mt9p031: Fix corrupted frame after restarting stream

From: Dirk Bender <d.bender@...tec.de>

[ Upstream commit 0961ba6dd211a4a52d1dd4c2d59be60ac2dc08c7 ]

To prevent corrupted frames after starting and stopping the sensor its
datasheet specifies a specific pause sequence to follow:

Stopping:
	Set Pause_Restart Bit -> Set Restart Bit -> Set Chip_Enable Off

Restarting:
	Set Chip_Enable On -> Clear Pause_Restart Bit

The Restart Bit is cleared automatically and must not be cleared
manually as this would cause undefined behavior.

Signed-off-by: Dirk Bender <d.bender@...tec.de>
Signed-off-by: Stefan Riedmueller <s.riedmueller@...tec.de>
Signed-off-by: Sakari Ailus <sakari.ailus@...ux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/media/i2c/mt9p031.c | 28 +++++++++++++++++++++++++++-
 1 file changed, 27 insertions(+), 1 deletion(-)

diff --git a/drivers/media/i2c/mt9p031.c b/drivers/media/i2c/mt9p031.c
index 0db15f528ac1c..fb60c9f42cb60 100644
--- a/drivers/media/i2c/mt9p031.c
+++ b/drivers/media/i2c/mt9p031.c
@@ -81,7 +81,9 @@
 #define		MT9P031_PIXEL_CLOCK_INVERT		(1 << 15)
 #define		MT9P031_PIXEL_CLOCK_SHIFT(n)		((n) << 8)
 #define		MT9P031_PIXEL_CLOCK_DIVIDE(n)		((n) << 0)
-#define MT9P031_FRAME_RESTART				0x0b
+#define MT9P031_RESTART					0x0b
+#define		MT9P031_FRAME_PAUSE_RESTART		(1 << 1)
+#define		MT9P031_FRAME_RESTART			(1 << 0)
 #define MT9P031_SHUTTER_DELAY				0x0c
 #define MT9P031_RST					0x0d
 #define		MT9P031_RST_ENABLE			1
@@ -448,9 +450,23 @@ static int mt9p031_set_params(struct mt9p031 *mt9p031)
 static int mt9p031_s_stream(struct v4l2_subdev *subdev, int enable)
 {
 	struct mt9p031 *mt9p031 = to_mt9p031(subdev);
+	struct i2c_client *client = v4l2_get_subdevdata(subdev);
+	int val;
 	int ret;
 
 	if (!enable) {
+		/* enable pause restart */
+		val = MT9P031_FRAME_PAUSE_RESTART;
+		ret = mt9p031_write(client, MT9P031_RESTART, val);
+		if (ret < 0)
+			return ret;
+
+		/* enable restart + keep pause restart set */
+		val |= MT9P031_FRAME_RESTART;
+		ret = mt9p031_write(client, MT9P031_RESTART, val);
+		if (ret < 0)
+			return ret;
+
 		/* Stop sensor readout */
 		ret = mt9p031_set_output_control(mt9p031,
 						 MT9P031_OUTPUT_CONTROL_CEN, 0);
@@ -470,6 +486,16 @@ static int mt9p031_s_stream(struct v4l2_subdev *subdev, int enable)
 	if (ret < 0)
 		return ret;
 
+	/*
+	 * - clear pause restart
+	 * - don't clear restart as clearing restart manually can cause
+	 *   undefined behavior
+	 */
+	val = MT9P031_FRAME_RESTART;
+	ret = mt9p031_write(client, MT9P031_RESTART, val);
+	if (ret < 0)
+		return ret;
+
 	return mt9p031_pll_enable(mt9p031);
 }
 
-- 
2.33.0