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

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Message-ID: <20181209233917.dhtwrpb46y2iyx4m@valkosipuli.retiisi.org.uk>
Date:   Mon, 10 Dec 2018 01:39:17 +0200
From:   sakari.ailus@....fi
To:     Jacopo Mondi <jacopo+renesas@...ndi.org>
Cc:     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 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...

-- 
Regards,

Sakari Ailus