RE: [PATCH] media: ov5675: use group write to update digital gain

Cao, Bingbu
2021-12-29T10:00:49Z

Hi Sakari,

Thanks for your review.

________________________
BRs,
Bingbu Cao

> -----Original Message-----
> From: Sakari Ailus <sakari.ailus@linux.intel.com>
> Sent: Wednesday, December 29, 2021 5:42 PM
> To: Cao, Bingbu <bingbu.cao@intel.com>
> Cc: linux-media@vger.kernel.org; Tu, ShawnX <shawnx.tu@intel.com>;
> senozhatsky@chromium.org; tfiga@chromium.org; bingbu.cao@linux.intel.com;
> Yeh, Andy <andy.yeh@intel.com>
> Subject: Re: [PATCH] media: ov5675: use group write to update digital
> gain
>
> Hi Bingbu,
>
> On Wed, Dec 29, 2021 at 04:57:39PM +0800, Bingbu Cao wrote:
> > MWB gain register are used to set gain for each mwb channel mannually.
> > However, it will involve some artifacts at low light environment as
> > gain cannot be applied to each channel synchronously. Update the
> > driver to use group write for digital gain to make the sure RGB
> > digital gain be applied together at frame boundary.
>
> How about the analogue gain and exposure time?
>
> Shouldn't they be applied similarly as well? Adding two more writes
> increases the probability of missing a frame there.

We did not meet issue related to analog gain as the it was applied by only
1 reg write, it looks like same issue we found on ov8856, changing to set
digital gain by only 1 global gain write will fix the problem.

>
> This is of course a trick since the control framework doesn't really
> support this, but I think this support should be added.
>
> --
> Regards,
>
> Sakari Ailus