Messages in this thread | | | Subject | Re: [PATCH v2 5/5] media: mt9p031: Fix corrupted frame after restarting stream | From | Stefan Riedmüller <> | Date | Mon, 5 Oct 2020 11:28:21 +0200 |
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Hi Laurent,
On 02.10.20 02:05, Laurent Pinchart wrote: > Hi Stefan, > > Thank you for the patch. > > On Wed, Sep 30, 2020 at 12:51:33PM +0200, Stefan Riedmueller wrote: >> From: Dirk Bender <d.bender@phytec.de> >> >> To prevent corrupted frames after starting and stopping the sensor it's > > s/it's/its/
thanks, I'll fix that.
> >> 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> >> --- >> No changes in v2 >> --- >> drivers/media/i2c/mt9p031.c | 25 +++++++++++++++++++++++++ >> 1 file changed, 25 insertions(+) >> >> diff --git a/drivers/media/i2c/mt9p031.c b/drivers/media/i2c/mt9p031.c >> index d10457361e6c..d59f66e3dcf3 100644 >> --- a/drivers/media/i2c/mt9p031.c >> +++ b/drivers/media/i2c/mt9p031.c >> @@ -80,6 +80,8 @@ >> #define MT9P031_PIXEL_CLOCK_SHIFT(n) ((n) << 8) >> #define MT9P031_PIXEL_CLOCK_DIVIDE(n) ((n) << 0) >> #define MT9P031_FRAME_RESTART 0x0b >> +#define MT9P031_FRAME_RESTART_SET (1 << 0) >> +#define MT9P031_FRAME_PAUSE_RESTART_SET (1 << 1) > > The fields are named Restart and Pause_Restart, I would drop _SET. Could > you also sort them from MSB to LSB as for the other registers ? Using > BIT() would be good too, although this could be done as an additional > patch to convert all the existing macros.
I'll do that. Also I will rename the register to MT9P031_RESTART and the bits to MT9P031_FRAME_RESTART and MT9P031_FRAME_PAUSE_RESTART.
> >> #define MT9P031_SHUTTER_DELAY 0x0c >> #define MT9P031_RST 0x0d >> #define MT9P031_RST_ENABLE 1 >> @@ -483,9 +485,25 @@ 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) { >> + val = mt9p031_read(client, MT9P031_FRAME_RESTART); > > Do you need to read the register ? Can't you write > MT9P031_FRAME_PAUSE_RESTART_SET and then MT9P031_FRAME_PAUSE_RESTART_SET > | MT9P031_FRAME_RESTART_SET ? And actually, can't we just write both > bits in one go, do we need two writes ?
I think you're right we don't necessarily need to read the registers. The only other bit is not used by the driver.
But I think we do need two separate writes, at least that is what the datasheet states.
So I would drop the read but keep both write, ok?
> >> + >> + /* enable pause restart */ >> + val |= MT9P031_FRAME_PAUSE_RESTART_SET; >> + ret = mt9p031_write(client, MT9P031_FRAME_RESTART, val); >> + if (ret < 0) >> + return ret; >> + >> + /* enable restart + keep pause restart set */ >> + val |= MT9P031_FRAME_RESTART_SET; >> + ret = mt9p031_write(client, MT9P031_FRAME_RESTART, val); >> + if (ret < 0) >> + return ret; >> + >> /* Stop sensor readout */ >> ret = mt9p031_set_output_control(mt9p031, >> MT9P031_OUTPUT_CONTROL_CEN, 0); >> @@ -505,6 +523,13 @@ static int mt9p031_s_stream(struct v4l2_subdev *subdev, int enable) >> if (ret < 0) >> return ret; >> >> + val = mt9p031_read(client, MT9P031_FRAME_RESTART); >> + /* disable reset + pause restart */ >> + val &= ~MT9P031_FRAME_PAUSE_RESTART_SET; > > Same here, I think you can simply write MT9P031_FRAME_PAUSE_RESTART_SET.
I'll drop the read here as well. But I need to make sure, that the Restart Bit is not cleared manually here.
Regards, Stefan
> >> + ret = mt9p031_write(client, MT9P031_FRAME_RESTART, val); >> + if (ret < 0) >> + return ret; >> + >> return mt9p031_pll_enable(mt9p031); >> } >> >
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