linux-kernel - Re: [RFC/patch 0/2] arm64: boot: dts: qcom: sm8150: enable framebuffer for Surface Duo

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Date:   Fri, 17 Dec 2021 18:16:05 +0100
From:   Konrad Dybcio <konrad.dybcio@...ainline.org>
To:     Felipe Balbi <balbi@...nel.org>, Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>
Cc:     Rob Herring <robh+dt@...nel.org>, linux-arm-msm@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        Felipe Balbi <felipe.balbi@...rosoft.com>,
        Gustave Monce <gustave.monce@...look.com>
Subject: Re: [RFC/patch 0/2] arm64: boot: dts: qcom: sm8150: enable
 framebuffer for Surface Duo


On 17.12.2021 13:57, Felipe Balbi wrote:
> From: Felipe Balbi <felipe.balbi@...rosoft.com>
>
> Hi folks,
>
> I'm trying to enable the framebuffer on Microsoft Surface Duo. Looking
> through some internal docs, it came to my attention that the bootloader
> will fill up the framebuffer address and size to a memory node names
> splash_region. Adding the node, I can see the address of the
> framebuffer. Creating the relevant framebuffer device using
> simple-framebuffer, I can't see it working. Tried dd if=/dev/urandom
> of=/dev/fb0 and fb-test. None of which manage to get rid of what's
> already on the screen, put there by the bootloader (platform Logo).
>
> Wondering if any of you have seen a behavior such as this and how did
> you manage to get framebuffer working on SM8150 (I see at least Sony
> Xperia has the node).
>
> Felipe Balbi (2):
>   arm64: boot: dts: qcom: sm8150: add a label for reserved-memory
>   arm64: boot: dts: qcom: surface duo: add minimal framebuffer
>
>  .../dts/qcom/sm8150-microsoft-surface-duo.dts | 19 +++++++++++++++++++
>  arch/arm64/boot/dts/qcom/sm8150.dtsi          |  2 +-
>  2 files changed, 20 insertions(+), 1 deletion(-)

Hi,


this issue is totally unique to the Duo and your bootloader configuration.


Gus (CCd, co-author of Lumia 950/XL patches) and I were dissecting this precise

issue (albeit for a different usecase) and in our testing it turned out that XBL likely

kills the display stack upon exiting Boot Services and jumping to LinuxLoader. This may

be a bug that comes from the legacy of this device, as exiting Boot Services would

be rather undesirable in that scenario..


One fix would be to ask the bootloader team to look into it and fix it from there,

otherwise you'd have to bring up the display using the DPU1 driver, or perhaps in a

third-stage-bootloader (pls don't do it for the sanity of us all :D)


You can see the thing happening during the boot animation when the Microsoft

logo goes black for a split second and then it reappears with the "Powered by Android"

splash a short while after.


P.S I don't have this device and I'm only speaking on behalf of what we discovered

on Gus's one.


Konrad