linux-kernel - Re: [PATCH V5 5/6] drm: bridge: samsung-dsim: Dynamically configure DPHY timing

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Message-ID: <7a83b8c1-88ff-0ae6-9c3b-d49fc08c7ac0@samsung.com>
Date:   Fri, 12 May 2023 23:02:25 +0200
From:   Marek Szyprowski <m.szyprowski@...sung.com>
To:     Adam Ford <aford173@...il.com>,
        Lucas Stach <l.stach@...gutronix.de>
Cc:     dri-devel@...ts.freedesktop.org, Marek Vasut <marex@...x.de>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        Robert Foss <rfoss@...nel.org>,
        Jonas Karlman <jonas@...boo.se>, aford@...conembedded.com,
        Frieder Schrempf <frieder.schrempf@...tron.de>,
        linux-kernel@...r.kernel.org, Michael Walle <michael@...le.cc>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Andrzej Hajda <andrzej.hajda@...el.com>,
        Chen-Yu Tsai <wenst@...omium.org>,
        Jagan Teki <jagan@...rulasolutions.com>
Subject: Re: [PATCH V5 5/6] drm: bridge: samsung-dsim: Dynamically configure
 DPHY timing

On 12.05.2023 22:00, Adam Ford wrote:
> On Fri, May 12, 2023 at 2:37 PM Lucas Stach <l.stach@...gutronix.de> wrote:
>> Am Samstag, dem 06.05.2023 um 14:24 -0500 schrieb Adam Ford:
>>> The DPHY timings are currently hard coded. Since the input
>>> clock can be variable, the phy timings need to be variable
>>> too.  Add an additional variable to the driver data to enable
>>> this feature to prevent breaking boards that don't support it.
>>>
>>> The phy_mipi_dphy_get_default_config function configures the
>>> DPHY timings in pico-seconds, and a small macro converts those
>>> timings into clock cycles based on the pixel clock rate.
>>>
>> This week I finally had some time to take a deeper look at this series
>> and test it on some of my systems.
> Thanks for testing this!
>> This patch causes issues when the burst clock rate is fixed by
>> supplying the DT entry. Instead of describing the issue below, I'm
>> attaching the patch that makes things work on my system.
> Oops, sorry about that.
>
>> I would appreciate if you could test this one on your side. Feel free
>> to squash it into yours if you find it working properly.
> I reviewed your patch, and it looks like it makes a lot of sense.
> If it works, I'll squash them together and add your name to the sign-off.
>
>> Also I would almost bet that dynamic_dphy is working on the Exynos
>> boards with that fix added. So if anyone with access to those boards
>> would like to give it a shot, we may be able to get rid of the
>> hardcoded PHY parameters altogether, which would be a nice cleanup.
> I wondered the same thing, but I didn't want to create more work for
> Marek S and since there was so much churn getting the original driver
> ported, I thought it would be the safest thing to try to give the
> imx8m m/n/p the features without breaking the Exynos.
>
> Marek S - Do you want me to post this file without the extra checks to
> see if it still works with Exynos?

Feel free to send me patches to test or just point to your 
work-in-progress git repo.


Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland