Re: [PATCH 1/2] media: i2c: ov5645: Move the register 0x3008 from ov5645_global_init_setting

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Hi Wolfram,

Thanks for the feedback.

On Tue, Feb 13, 2024 at 10:27 PM Wolfram Sang <wsa@xxxxxxxxxx> wrote:
>
> Hi Biju,
>
> I couldn't find a datasheet for the OV5645 but the one for OV5642 looked
> pretty similar when it comes to the issues mentioned here.

I don't have the data sheet. I am just debugging with a picoscope.

>
> > Testing OV5645 with i2c bus frequency @400kHz on RZ/G2L SMARC EVL platform
> > shows issues like the captured image is either greenish or it is not
> > capturing the image at all. However, It is working ok when the i2c
> > frequency is 100kHz. From this, it is clear that we have a timing issue
> > at high speed. The testing also shows that if we add a delay >= 1 msec
>
> That could match the "VDD stable to sensor stable" delay in the
> datasheet.

I think it is different here. That 1 msec is delay associated with
applying hardware power see [1]

[1]
https://elixir.bootlin.com/linux/latest/source/drivers/media/i2c/ov5645.c#L667


>
> > after register write {0x3008, 0x82}, then the captured image is always
> > good. So, move the register 0x3008 and 0x3103 from ov5645_*_init_setting
> > to a new table ov5645_global_init_setting.
> >
> > Drop the unnecessary entry { 0x3008, 0x42 } from ov5645_*init_setting
> > table at the start.
>
> It seems this is not needed to fix your issue? Then, this would be a
> seperate change with a dedicated reason, I'd think. There is another
> pair of activating power-down mode and immediately disabling it again.
> Either we simplify it, too, or we leave both in place. Or at least make
> sure there wasn't a reason for them. I'd just leave them.

My bad. I thought as per [2], there are 2 writes for 0x3008, so I
should take out the redundant one.
I will restore it.

[2]
https://patchwork.kernel.org/project/linux-renesas-soc/patch/20240126133116.121981-6-biju.das.jz@xxxxxxxxxxxxxx/#25706558

Cheers,
Biju





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