linux-kernel - Re: [PATCH] v4l2: i2c: ov7670: Fix PLL bypass register values

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Date:   Mon, 10 Dec 2018 08:59:02 +0100
From:   jacopo mondi <jacopo@...ndi.org>
To:     sakari.ailus@....fi
Cc:     Jacopo Mondi <jacopo+renesas@...ndi.org>, corbet@....net,
        mchehab@...nel.org, linux-media@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] v4l2: i2c: ov7670: Fix PLL bypass register values

Hi Sakari,
   thanks for digging this out

On Mon, Dec 10, 2018 at 01:39:17AM +0200, sakari.ailus@....fi wrote:
> Hi Jacopo,
>
> On Fri, Dec 29, 2017 at 01:22:26PM +0100, Jacopo Mondi wrote:
> > The following commits:
> > commit f6dd927f34d6 ("[media] media: ov7670: calculate framerate properly for ov7675")
> > commit 04ee6d92047e ("[media] media: ov7670: add possibility to bypass pll for ov7675")
> > introduced the ability to bypass PLL multiplier and use input clock (xvclk)
> > as pixel clock output frequency for ov7675 sensor.
> >
> > PLL is bypassed using register DBLV[7:6], according to ov7670 and ov7675
> > sensor manuals. Macros used to set DBLV register seem wrong in the
> > driver, as their values do not match what reported in the datasheet.
> >
> > Fix by changing DBLV_* macros to use bits [7:6] and set bits [3:0] to
> > default 0x0a reserved value (according to datasheets).
> >
> > While at there, remove a write to DBLV register in
> > "ov7675_set_framerate()" that over-writes the previous one to the same
> > register that takes "info->pll_bypass" flag into account instead of setting PLL
> > multiplier to 4x unconditionally.
> >
> > And, while at there, since "info->pll_bypass" is only used in
> > set/get_framerate() functions used by ov7675 only, it is not necessary
> > to check for the device id at probe time to make sure that when using
> > ov7670 "info->pll_bypass" is set to false.
> >
> > Signed-off-by: Jacopo Mondi <jacopo+renesas@...ndi.org>
>
> I assume this is still valid and long overdue for merging. :-) No other
> work in the area seem to have been done so I'm picking it up...
>

It should still be valid, and should still apply regardless of its
age :) Is it worth a proper 'Fixes' tag?

Fixes: f6dd927f34d6 ("[media] media: ov7670: calculate framerate properly for ov7675")

Thanks
  j

> --
> Regards,
>
> Sakari Ailus

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