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    Subject[PATCH 5.15 218/917] media: mt9p031: Fix corrupted frame after restarting stream
    Date
    From: Dirk Bender <d.bender@phytec.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@phytec.de>
    Signed-off-by: Stefan Riedmueller <s.riedmueller@phytec.de>
    Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
    Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
    Signed-off-by: Sasha Levin <sashal@kernel.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 6eb88ef997836..3ae1b28c8351b 100644
    --- a/drivers/media/i2c/mt9p031.c
    +++ b/drivers/media/i2c/mt9p031.c
    @@ -78,7 +78,9 @@
    #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
    @@ -444,9 +446,23 @@ 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);
    @@ -466,6 +482,16 @@ 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


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