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From:   Stefan Riedmueller <s.riedmueller@phytec.de>
To:     Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
        Mauro Carvalho Chehab <mchehab@kernel.org>,
        Rob Herring <robh+dt@kernel.org>
Cc:     Dirk Bender <d.bender@phytec.de>,
        Stefan Riedmueller <s.riedmueller@phytec.de>,
        Sakari Ailus <sakari.ailus@linux.intel.com>,
        linux-media@vger.kernel.org, devicetree@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: [PATCH v6 3/6] media: mt9p031: Fix corrupted frame after restarting stream
Date:   Wed, 14 Jul 2021 15:38:46 +0200
Message-Id: <20210714133849.1041619-4-s.riedmueller@phytec.de>
In-Reply-To: <20210714133849.1041619-1-s.riedmueller@phytec.de>
References: <20210714133849.1041619-1-s.riedmueller@phytec.de>
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From: Dirk Bender <d.bender@phytec.de>

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

Stopping:
	Set Pause=5FRestart Bit -> Set Restart Bit -> Set Chip=5FEnable Off

Restarting:
	Set Chip=5FEnable On -> Clear Pause=5FRestart 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@phytec.de>
Signed-off-by: Stefan Riedmueller <s.riedmueller@phytec.de>
---
 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 ea90aff576ba..ee2777059682 100644
--- a/drivers/media/i2c/mt9p031.c
+++ b/drivers/media/i2c/mt9p031.c
@@ -79,7 +79,9 @@
 #define		MT9P031=5FPIXEL=5FCLOCK=5FINVERT		(1 << 15)
 #define		MT9P031=5FPIXEL=5FCLOCK=5FSHIFT(n)		((n) << 8)
 #define		MT9P031=5FPIXEL=5FCLOCK=5FDIVIDE(n)		((n) << 0)
-#define MT9P031=5FFRAME=5FRESTART				0x0b
+#define MT9P031=5FRESTART					0x0b
+#define		MT9P031=5FFRAME=5FPAUSE=5FRESTART		(1 << 1)
+#define		MT9P031=5FFRAME=5FRESTART			(1 << 0)
 #define MT9P031=5FSHUTTER=5FDELAY				0x0c
 #define MT9P031=5FRST					0x0d
 #define		MT9P031=5FRST=5FENABLE			1
@@ -456,9 +458,23 @@ static int mt9p031=5Fset=5Fparams(struct mt9p031 *mt9p=
031)
 static int mt9p031=5Fs=5Fstream(struct v4l2=5Fsubdev *subdev, int enable)
 {
 	struct mt9p031 *mt9p031 =3D to=5Fmt9p031(subdev);
+	struct i2c=5Fclient *client =3D v4l2=5Fget=5Fsubdevdata(subdev);
+	int val;
 	int ret;
=20
 	if (!enable) {
+		/* enable pause restart */
+		val =3D MT9P031=5FFRAME=5FPAUSE=5FRESTART;
+		ret =3D mt9p031=5Fwrite(client, MT9P031=5FRESTART, val);
+		if (ret < 0)
+			return ret;
+
+		/* enable restart + keep pause restart set */
+		val |=3D MT9P031=5FFRAME=5FRESTART;
+		ret =3D mt9p031=5Fwrite(client, MT9P031=5FRESTART, val);
+		if (ret < 0)
+			return ret;
+
 		/* Stop sensor readout */
 		ret =3D mt9p031=5Fset=5Foutput=5Fcontrol(mt9p031,
 						 MT9P031=5FOUTPUT=5FCONTROL=5FCEN, 0);
@@ -478,6 +494,16 @@ static int mt9p031=5Fs=5Fstream(struct v4l2=5Fsubdev *=
subdev, int enable)
 	if (ret < 0)
 		return ret;
=20
+	/*
+	 * - clear pause restart
+	 * - don't clear restart as clearing restart manually can cause
+	 *   undefined behavior
+	 */
+	val =3D MT9P031=5FFRAME=5FRESTART;
+	ret =3D mt9p031=5Fwrite(client, MT9P031=5FRESTART, val);
+	if (ret < 0)
+		return ret;
+
 	return mt9p031=5Fpll=5Fenable(mt9p031);
 }
=20
--=20
2.25.1