Re: [PATCH v2 1/5] media: i2c: imx335: Drop setting of 0x3a00 register

[Umang Jain]

Hi,

On 1/31/24 4:02 PM, Matthias Fend wrote:
> Hi Kieran,
>
> Am 31.01.2024 um 10:52 schrieb Kieran Bingham:
> > Hi Umang,
> >
> > + Cc: Matthias
> >
> > Quoting Umang Jain (2024-01-31 05:52:04)
> > > Register 0x3a00 is a reserved field as per the IMX335 datasheet,
> > > hence shouldn't be set by the driver.
> >
> > We still need to explain more about why we're dropping this register
> > write, and what effects it causes.
> >
> > Matthias - I believe this stemmed from the work you did, and I think I
> > recall that you stated this register write broke the CSI2 configuration?
> >
> > Can you clarify anything here for us please?
>
> yes, that's correct.
>
> Since this driver originally did not work in my setup, I came across 
> this register while searching for differences to my working reference 
> configuration.
> With the default value of this register (0x00), the driver works 
> perfectly. With the value previously written to it by the driver 
> (0x01), I cannot receive any frames.
> The problem may depend on the link frequency used.
> I can only use and test a frequency of 445.5MHz on my hardware. Since 
> only link frequencies of 594MHz were supported so far, this may not 
> have been a problem.
>
> Unfortunately I do not have a description of this register, so I can 
> only speculate about the exact cause.

Is it worth to frame the commit message around this speculation ?

My setup has no effect with this register being set or not.
> ~Matthias
>
> > --
> > Kieran
> >
> >
> > > Signed-off-by: Umang Jain <umang.jain@xxxxxxxxxxxxxxxx>
> > > ---
> > >   drivers/media/i2c/imx335.c | 1 -
> > >   1 file changed, 1 deletion(-)
> > >
> > > diff --git a/drivers/media/i2c/imx335.c b/drivers/media/i2c/imx335.c
> > > index 7a37eb327ff4..927b4806a5d7 100644
> > > --- a/drivers/media/i2c/imx335.c
> > > +++ b/drivers/media/i2c/imx335.c
> > > @@ -249,7 +249,6 @@ static const struct imx335_reg 
> > > mode_2592x1940_regs[] = {
> > >          {0x3794, 0x7a},
> > >          {0x3796, 0xa1},
> > >          {0x37b0, 0x36},
> > > -       {0x3a00, 0x01},
> > >   };
> > >     static const struct imx335_reg raw10_framefmt_regs[] = {
> > > --
> > > 2.41.0