Hi Stefan, On Mon, Oct 05, 2020 at 11:28:21AM +0200, Stefan Riedmüller wrote: > On 02.10.20 02:05, Laurent Pinchart wrote: > > On Wed, Sep 30, 2020 at 12:51:33PM +0200, Stefan Riedmueller wrote: > >> From: Dirk Bender <[email protected]> > >> > >> 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 <[email protected]> > >> Signed-off-by: Stefan Riedmueller <[email protected]> > >> --- > >> 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?
That's fine with me if required, although I don't see where this is indicated in the datasheet, but I may have missed it. > >> + > >> + /* 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. > > >> + ret = mt9p031_write(client, MT9P031_FRAME_RESTART, val); > >> + if (ret < 0) > >> + return ret; > >> + > >> return mt9p031_pll_enable(mt9p031); > >> } > >> -- Regards, Laurent Pinchart
