Re: [PATCH RESEND v2 06/12] drm/sun4i: rgb: Add 1% tolerance to dclk frequency check when bridge is connected

Icenowy Zheng
2019-02-04T16:28:21Z

于 2019年2月5日 GMT+08:00 上午12:26:43, Vasily Khoruzhick <anarsoul-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> 写到:
>On Mon, Feb 4, 2019 at 6:20 AM Maxime Ripard
><maxime.ripard-LDxbnhwyfcJBDgjK7y7TUQ@public.gmane.org> wrote:
>>
>> Hi,
>>
>> On Sun, Feb 03, 2019 at 10:54:55AM -0800, Vasily Khoruzhick wrote:
>> > Clock rate check that was added in commit bb43d40d7c83 ("drm/sun4i:
>rgb:
>> > Validate the clock rate") prevents some panel and bridges from
>working with
>> > sun4i driver.
>> >
>> > Unfortunately, dotclock frequency for some modes are not achievable
>on
>> > sunxi hardware, and there's a slight deviation in rate returned by
>> > clk_round_rate(), so they fail this check.
>> >
>> > Experiments show that panels and bridges work fine with this slight
>> > deviation, e.g. Pinebook that uses ANX6345 bridge with 768p eDP
>panel
>> > requests 73 MHz, gets 72.296MHz instead (0.96% difference) and
>works just
>> > fine.
>> >
>> > This patch adds a 1% tolerence to the dot clock check when bridge
>is
>> > connected.
>> >
>> > Signed-off-by: Vasily Khoruzhick <anarsoul-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
>>
>> I'm not sure we want to make exceptions for all the hardware
>> combination we face, but we should go for something more generic (and
>> easier to maintain instead).
>>
>> IIRC, from the previous discussion, HDMI had a tolerancy requirement
>> in the standard. Do you know if there's such a thing for eDP? That
>> would solve the issue for all the eDP displays at once.
>
>I don't have access to eDP standard - vesa.org says it's available to
>members only.

Try out to grab an old version?

I remember 1.0 is open.

>
>> Maxime
>>
>> --
>> Maxime Ripard, Bootlin
>> Embedded Linux and Kernel engineering
>> https://bootlin.com
>
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