linux-kernel - Re: [PATCH v4 0/6] drm: lcdif: Add i.MX93 LCDIF support

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Message-ID: <ed28bbda-16b6-043b-5310-8ac0e8ebd900@prevas.dk>
Date:   Mon, 20 Feb 2023 13:18:59 +0100
From:   Rasmus Villemoes <rasmus.villemoes@...vas.dk>
To:     Alexander Stein <alexander.stein@...tq-group.com>,
        dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        Liu Ying <victor.liu@....com>
Cc:     marex@...x.de, stefan@...er.ch, airlied@...il.com, daniel@...ll.ch,
        robh+dt@...nel.org, krzysztof.kozlowski+dt@...aro.org,
        shawnguo@...nel.org, s.hauer@...gutronix.de, kernel@...gutronix.de,
        festevam@...il.com, linux-imx@....com,
        krzysztof.kozlowski@...aro.org, LW@...o-electronics.de
Subject: Re: [PATCH v4 0/6] drm: lcdif: Add i.MX93 LCDIF support

On 17/02/2023 09.18, Alexander Stein wrote:
> Hi Liu,
> 
> Am Freitag, 17. Februar 2023, 07:54:01 CET schrieb Liu Ying:
>> Hi,
>>
>> This patch set aims to add i.MX93 LCDIF display controller support
>> in the existing LCDIF DRM driver.  The LCDIF embedded in i.MX93 SoC
>> is essentially the same to those embedded in i.MX8mp SoC.  Through
>> internal bridges, i.MX93 LCDIF may drive a MIPI DSI display or a LVDS
>> display or a parallel display.
>>
>> Patch 1/6 adds device tree binding support for i.MX93 LCDIF in the
>> existing fsl,lcdif.yaml.
>>
>> Patch 2/6 drops lcdif->bridge NULL pointer check as a cleanup patch.
>>
>> Patch 3/6~5/6 prepare for adding i.MX93 LCDIF support step by step.
>>
>> Patch 6/6 adds i.MX93 LCDIF compatible string as the last step of
>> adding i.MX93 LCDIF support.
> 
> Thanks for the series. I could test this on my TQMa93xxLA/MBa93xxCA with a 
> single LVDS display attached, so no DSI or parallel display. Hence I could not 
> test the bus format and flags checks, but they look okay.
> So you can add
> Tested-by: Alexander Stein <alexander.stein@...tq-group.com>
> to the whole series as well.
> 
> One thing I noticed is that, sometimes it seems that before probing lcdif my 
> system completely freezes. Adding some debug output it seems that's during 
> powering up the IMX93_MEDIABLK_PD_LCDIF power domain there is some race 
> condition. But adding more more detailed output made the problem go away.
> Did you notice something similar? It might be a red hering though.

Interesting. Sounds similar to what I encountered on several
imx8mp-based boards, both the NXP EVK and our custom design, running a
mainline U-Boot and downstream NXP kernel:

https://lore.kernel.org/u-boot/20220823133645.4046432-1-rasmus.villemoes@prevas.dk/

I never really found a real solution, but as the hack I ended up
applying in U-Boot does involve some clock settings, and you apparently
now figured out some connection to "overclocking", I do think these
issues are related.

Rasmus