linux-kernel - Re: [PATCH v2] arm64: dts: qcom: sm8250-edo: Panel framebuffer is 2.5k instead of 4k

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Message-ID: <057386c7-a7cf-14cb-d564-1b30e79806f6@collabora.com>
Date:   Wed, 14 Jun 2023 15:13:44 +0200
From:   AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
To:     Konrad Dybcio <konrad.dybcio@...aro.org>,
        Marijn Suijten <marijn.suijten@...ainline.org>,
        phone-devel@...r.kernel.org, ~postmarketos/upstreaming@...ts.sr.ht,
        Martin Botka <martin.botka@...ainline.org>,
        Jami Kettunen <jami.kettunen@...ainline.org>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] arm64: dts: qcom: sm8250-edo: Panel framebuffer is
 2.5k instead of 4k

Il 14/06/23 14:43, Konrad Dybcio ha scritto:
> On 14.06.2023 14:40, Marijn Suijten wrote:
>> On 2023-06-07 09:15:08, AngeloGioacchino Del Regno wrote:
>>> Il 07/06/23 00:52, Konrad Dybcio ha scritto:
>>>>
>>>>
>>>> On 6.06.2023 23:14, Marijn Suijten wrote:
>>>>> The framebuffer configuration for edo pdx203, written in edo dtsi (which
>>>>> is overwritten in pdx206 dts for its smaller panel) has to use a
>>>>> 1096x2560 configuration as this is what the panel (and framebuffer area)
>>>>> has been initialized to.  Downstream userspace also has access to (and
>>>>> uses) this 2.5k mode by default, and only switches the panel to 4k when
>>>>> requested.
>>>>>
>>>>> This is similar to commit be8de06dc397 ("arm64: dts: qcom:
>>>>> sm8150-kumano: Panel framebuffer is 2.5k instead of 4k") which fixed the
>>>>> same for the previous generation Sony platform.
>>>>>
>>>>> Fixes: 69cdb97ef652 ("arm64: dts: qcom: sm8250: Add support for SONY Xperia 1 II / 5 II (Edo platform)")
>>>>> Signed-off-by: Marijn Suijten <marijn.suijten@...ainline.org>
>>>>> ---
>>>> And so I derped again.
>>>>
>>>> Reviewed-by: Konrad Dybcio <konrad.dybcio@...aro.org>
>>>
>>> I would've liked more to see a commit saying "replace simple-framebuffer with xxxx"
>>> (where xxxx is DSI panel, etc) but that will as well do for now... :-)
>>
>> Fwiw we could keep it around as MDSS "gracefully" takes over when it
>> probes a little bit later with fbcon over DRM/KMS, and it sometimes
>> helps reading what is up when something fails before or during MDSS
>> probe.
> I believe we should do this. Perhaps even add some early code to drm/msm
> that'd read out the address (and other configuration) from the mdp hw and
> set it up automagically.
> 

As far as I remember, some bootloaders are reading devicetrees to setup the display
at boot with "continuous splash", that's why I would be for *replacing* the simple
framebuffer with the mdss-dsi.

Adding early code to drm/msm to read out the address and check the state of the HW
before pushing an early framebuffer would be a definitive solution for that corner
case. Good call, Konrad.

Cheers,
Angelo

> Konrad
>>
>> - Marijn
>>
>>> Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
>>>
>>>>
>>>> Konrad
>>>>>
>>>>> Changes since v2:
>>>>> - Rename griffin (copy-paste from related patch) to pdx203 in comment.
>>>>>
>>>>>    arch/arm64/boot/dts/qcom/sm8250-sony-xperia-edo.dtsi | 7 ++++---
>>>>>    1 file changed, 4 insertions(+), 3 deletions(-)
>>>>>
>>>>> diff --git a/arch/arm64/boot/dts/qcom/sm8250-sony-xperia-edo.dtsi b/arch/arm64/boot/dts/qcom/sm8250-sony-xperia-edo.dtsi
>>>>> index 3d22be747f042..8f867f841cb83 100644
>>>>> --- a/arch/arm64/boot/dts/qcom/sm8250-sony-xperia-edo.dtsi
>>>>> +++ b/arch/arm64/boot/dts/qcom/sm8250-sony-xperia-edo.dtsi
>>>>> @@ -54,9 +54,10 @@ chosen {
>>>>>    		framebuffer: framebuffer@...00000 {
>>>>>    			compatible = "simple-framebuffer";
>>>>>    			reg = <0 0x9c000000 0 0x2300000>;
>>>>> -			width = <1644>;
>>>>> -			height = <3840>;
>>>>> -			stride = <(1644 * 4)>;
>>>>> +			/* pdx203 BL initializes in 2.5k mode, not 4k */
>>>>> +			width = <1096>;
>>>>> +			height = <2560>;
>>>>> +			stride = <(1096 * 4)>;
>>>>>    			format = "a8r8g8b8";
>>>>>    		};
>>>>>    	};
>>>