Re: [PATCH 2/2] media: ov5640: Fix auto-exposure disabling

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HI Laurent,

On Thu, Sep 06, 2018 at 08:08:50PM +0300, Laurent Pinchart wrote:
> Hello,
>
> On Tuesday, 14 August 2018 18:45:25 EEST jacopo mondi wrote:
> > On Tue, Aug 07, 2018 at 08:53:23AM +0000, Hugues FRUCHET wrote:
> > > Hi Jacopo,
> > >
> > > In serie "[PATCH 0/5] Fix OV5640 exposure & gain"
> > > https://www.mail-archive.com/linux-media@xxxxxxxxxxxxxxx/msg133269.html
> > > I've tried to collect fixes around exposure/gain, not only the exposure
> > > regression and I would prefer to keep it consistent with the associated
> > > procedure test.
> >
> > You're right. Please see my other reply, I mixed two different issues
> > in this series probably.
> >
> > > Moreover I dislike the internal use of control framework functions to
> > > disable/enable exposure/gain, on my opinion this has to be kept simpler
> > > by just disabling/enabling the right registers.
> >
> > Why that? I thought changing parameters exposed as controls should go
> > through the control framework to ensure consistency. Maybe I'm wrong.
>
> If I understand the driver correctly, auto-exposure has to be disabled
> temporarily when changing format and size, due to internal hardware
> requirements. The sequence should more or less be
>
>  1. Disable auto-exposure
>  2. Configure the format and size
>  3. Restore auto-exposure
>
> This sequence is internal to the driver, and should thus not be visible to
> userspace. Going through the control framework to disable and restore auto-
> exposure would generate control events that would just confuse userspace. For
> that reason I'd keep all this internal with direct register access instead of
> going through the control framework.

Thanks for the clarification.

Please note this series is superseded by Hugues' exposure and gain
fixes one, and my MIPI CSI-2 startup one (as it includes the timings
fix also sent there).

Thanks
   j
>
> > > Would it be possible that you test my 5 patches serie on your side ?
> >
> > I did. I re-based the series on top of my MIPI and timings fixes and
> > it actually solves the exposure issues I didn't know I had :)
> >
> > I'll comment on v2 as well as soon as I'll get an answer from Steve on
> > the CSI-2 issue.
> >
> > > On 07/18/2018 03:04 PM, jacopo mondi wrote:
> > > > Hi again,
> > > >
> > > > On Wed, Jul 18, 2018 at 01:19:03PM +0200, Jacopo Mondi wrote:
> > > >> As of:
> > > >> commit bf4a4b518c20 ("media: ov5640: Don't force the auto exposure
> > > >> state at
> > > >> start time") auto-exposure got disabled before programming new capture
> > > >> modes to the sensor. Unfortunately the function used to do that
> > > >> (ov5640_set_exposure()) does not enable/disable auto-exposure engine
> > > >> through register 0x3503[0] bit, but programs registers [0x3500 -
> > > >> 0x3502] which represent the desired exposure time when running with
> > > >> manual exposure. As a result, auto-exposure was not actually disabled
> > > >> at all.
> > > >>
> > > >> To actually disable auto-exposure, go through the control framework
> > > >> instead of calling ov5640_set_exposure() function directly.
> > > >>
> > > >> Also, as auto-gain and auto-exposure are disabled un-conditionally but
> > > >> only
> > > >> restored to their previous values in ov5640_set_mode_direct() function,
> > > >> move controls restoring so that their value is re-programmed
> > > >> opportunely after either ov5640_set_mode_direct() or
> > > >> ov5640_set_mode_exposure_calc() have been executed.
> > > >>
> > > >> Fixes: bf4a4b518c20 ("media: ov5640: Don't force the auto exposure
> > > >> state at start time") Signed-off-by: Jacopo Mondi <jacopo@xxxxxxxxxx>
> > > >>
> > > >> ---
> > > >> Is it worth doing with auto-gain what we're doing with auto-exposure?
> > > >> Cache the value and then re-program it instead of unconditionally
> > > >> disable/enable it?> >
> > > > I have missed this patch from Hugues that address almost the same
> > > > issue
> > > > https://www.mail-archive.com/linux-media@xxxxxxxxxxxxxxx/msg133264.html
> > > >
> > > > I feel this new one is simpler, and unless we want to avoid going
> > > > through the control framework, it is not worth adding new functions to
> > > > handle auto-exposure as Hugues' patch is doing.
> > > >
> > > > Hugues, do you have comments? Feel free to add your sob or rb tags if
> > > > you like to.
> > > >
> > > > Thanks
> > > >
> > > >     j
> > > >>
> > > >> Thanks
> > > >>
> > > >>    j
> > > >>
> > > >> ---
> > > >> ---
> > > >>
> > > >>   drivers/media/i2c/ov5640.c | 29 +++++++++++++----------------
> > > >>   1 file changed, 13 insertions(+), 16 deletions(-)
> > > >>
> > > >> diff --git a/drivers/media/i2c/ov5640.c b/drivers/media/i2c/ov5640.c
> > > >> index 12b3496..bc75cb7 100644
> > > >> --- a/drivers/media/i2c/ov5640.c
> > > >> +++ b/drivers/media/i2c/ov5640.c
> > > >> @@ -1588,25 +1588,13 @@ static int ov5640_set_mode_exposure_calc(struct
> > > >> ov5640_dev *sensor,> >>
> > > >>    * change mode directly
> > > >>    */
> > > >>
> > > >>   static int ov5640_set_mode_direct(struct ov5640_dev *sensor,
> > > >>
> > > >> -				  const struct ov5640_mode_info *mode,
> > > >> -				  s32 exposure)
> > > >> +				  const struct ov5640_mode_info *mode)
> > > >>
> > > >>   {
> > > >>
> > > >> -	int ret;
> > > >> -
> > > >>
> > > >>   	if (!mode->reg_data)
> > > >>
> > > >>   		return -EINVAL;
> > > >>
> > > >>   	/* Write capture setting */
> > > >>
> > > >> -	ret = ov5640_load_regs(sensor, mode);
> > > >> -	if (ret < 0)
> > > >> -		return ret;
> > > >> -
> > > >> -	/* turn auto gain/exposure back on for direct mode */
> > > >> -	ret = __v4l2_ctrl_s_ctrl(sensor->ctrls.auto_gain, 1);
> > > >> -	if (ret)
> > > >> -		return ret;
> > > >> -
> > > >> -	return __v4l2_ctrl_s_ctrl(sensor->ctrls.auto_exp, exposure);
> > > >> +	return  ov5640_load_regs(sensor, mode);
> > > >>
> > > >>   }
> > > >>
> > > >>   static int ov5640_set_mode(struct ov5640_dev *sensor,
> > > >>
> > > >> @@ -1626,7 +1614,7 @@ static int ov5640_set_mode(struct ov5640_dev
> > > >> *sensor,
> > > >>
> > > >>   		return ret;
> > > >>
> > > >>   	exposure = sensor->ctrls.auto_exp->val;
> > > >>
> > > >> -	ret = ov5640_set_exposure(sensor, V4L2_EXPOSURE_MANUAL);
> > > >> +	ret = __v4l2_ctrl_s_ctrl(sensor->ctrls.auto_exp,
> > > >> V4L2_EXPOSURE_MANUAL);
> > > >>
> > > >>   	if (ret)
> > > >>
> > > >>   		return ret;
> > > >>
> > > >> @@ -1642,12 +1630,21 @@ static int ov5640_set_mode(struct ov5640_dev
> > > >> *sensor,> >>
> > > >>   		 * change inside subsampling or scaling
> > > >>   		 * download firmware directly
> > > >>   		 */
> > > >>
> > > >> -		ret = ov5640_set_mode_direct(sensor, mode, exposure);
> > > >> +		ret = ov5640_set_mode_direct(sensor, mode);
> > > >>
> > > >>   	}
> > > >>
> > > >>   	if (ret < 0)
> > > >>
> > > >>   		return ret;
> > > >>
> > > >> +	/* Restore auto-gain and auto-exposure after mode has changed. */
> > > >> +	ret = __v4l2_ctrl_s_ctrl(sensor->ctrls.auto_gain, 1);
> > > >> +	if (ret)
> > > >> +		return ret;
> > > >> +
> > > >> +	ret = __v4l2_ctrl_s_ctrl(sensor->ctrls.auto_exp, exposure)
> > > >> +	if (ret)
> > > >> +		return ret;
> > > >> +
> > > >>
> > > >>   	ret = ov5640_set_binning(sensor, dn_mode != SCALING);
> > > >>   	if (ret < 0)
> > > >>
> > > >>   		return ret;
> > > >>
> > > >> --
> > > >> 2.7.4
>
>
> --
> Regards,
>
> Laurent Pinchart
>
>
>

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