Re: [PATCH 1/3] media: ov5640: Handle delays when no reset_gpio set

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On Fri, Dec 16, 2022 at 8:09 AM Sakari Ailus
<sakari.ailus@xxxxxxxxxxxxxxx> wrote:
>
> Hi Jai,
>
> Thanks for the set.
>
> On Fri, Dec 16, 2022 at 07:14:07PM +0530, Jai Luthra wrote:
> > Some module manufacturers [1][2] don't expose the RESETB gpio of the
> > sensor directly through the 15-pin FFC connector. Instead wiring ~PWDN
> > as a proxy reset with appropriate delays.
> >
> > In such cases, reset_gpio will not be available to the driver, but it
> > will still be toggled when the sensor is powered on, and thus we should
> > still honor the wait time of >= 5ms + 1ms + 20ms (see figure 2-3 in [3])
> > before attempting any i/o operations over SCCB.
> >
> > [1] https://digilent.com/reference/_media/reference/add-ons/pcam-5c/pcam_5c_sch.pdf
> > [2] https://www.alinx.com/public/upload/file/AN5641_User_Manual.pdf
> > [3] https://cdn.sparkfun.com/datasheets/Sensors/LightImaging/OV5640_datasheet.pdf
> >
> > Fixes: 19a81c1426c1 ("[media] add Omnivision OV5640 sensor driver")
> > Signed-off-by: Jai Luthra <j-luthra@xxxxxx>
> > ---
> >  drivers/media/i2c/ov5640.c | 1 +
> >  1 file changed, 1 insertion(+)
> >
> > diff --git a/drivers/media/i2c/ov5640.c b/drivers/media/i2c/ov5640.c
> > index e0f908af581b..4bb7bf557cfa 100644
> > --- a/drivers/media/i2c/ov5640.c
> > +++ b/drivers/media/i2c/ov5640.c
> > @@ -2466,6 +2466,7 @@ static int ov5640_set_power_on(struct ov5640_dev *sensor)
> >
> >       ov5640_reset(sensor);
> >       ov5640_power(sensor, true);
> > +     usleep_range(26000, 30000);
>
> I think you should only do this if you don't have RESETB pin.
>
> I'm not sure how to best describe this in DT. It's not the same as if you
> didn't have RESETB GPIO.


 Can that function check if (!sensor->reset_gpio) and do the delay
only if reset_gpio is not present?

adam


>
> Cc the devicetree list and Krzysztof.
>
> >
> >       ret = ov5640_init_slave_id(sensor);
> >       if (ret)
>
> --
> Kind regards,
>
> Sakari Ailus



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