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media: mt9p031: Fix corrupted frame after restarting stream 

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>
This commit is contained in:
Dirk Bender 2021-07-26 09:35:15 +02:00 committed by Mauro Carvalho Chehab
parent ae47ee5fc4
commit 0961ba6dd2
1 changed files with 27 additions and 1 deletions
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28
drivers/media/i2c/mt9p031.c
View File

@ -79,7 +79,9 @@
#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
@ -456,9 +458,23 @@ 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);
@ -478,6 +494,16 @@ 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);
}