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Message-ID: <f30ba74d-62c9-4f91-929e-a3c6d074deeb@linaro.org>
Date:   Thu, 14 Dec 2023 12:58:04 +0100
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Subject: Re: [PATCH] arm64: dts: qcom: sc7180: Switch pompom to the generic
 edp-panel
Content-Language: en-US
To:     Douglas Anderson <dianders@chromium.org>,
        Bjorn Andersson <andersson@kernel.org>
Cc:     Stephen Boyd <swboyd@chromium.org>, Andy Gross <agross@kernel.org>,
        Conor Dooley <conor+dt@kernel.org>,
        Hsin-Yi Wang <hsinyi@chromium.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Rob Herring <robh+dt@kernel.org>,
        cros-qcom-dts-watchers@chromium.org, devicetree@vger.kernel.org,
        linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org
References: <20231213163501.1.I8c20f926d15c9ddc12e423e07df1e89db1105d93@changeid>
From:   Konrad Dybcio <konrad.dybcio@linaro.org>
In-Reply-To: <20231213163501.1.I8c20f926d15c9ddc12e423e07df1e89db1105d93@changeid>
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On 12/14/23 01:35, Douglas Anderson wrote:
> Pompom has several sources for its panel. Let's switch it to the
> generic edp-panel compatible string to account for this.
> 
> This fixes a problem where the panel wouldn't come up on some pompon
> devices after commit fb3f43d50d9b ("drm/panel-edp: Avoid adding
> multiple preferred modes"). Specifically, some models of pompom have a
> 1920x1080 panel which is _very_ different than the 1366x768 panel
> specified in the dts. Before the recent panel-edp fix on Linux things
> kinda/sorta worked because the panel-edp driver would include both the
> hardcoded and probed mode, AKA:
> 
> * #0 1920x1080
>    60.00 1920 1944 1960 2000 1080 1083 1088 1111 133320
>    flags: nhsync, nvsync; type: preferred, driver
> * #1 1366x768
>    60.00 1366 1406 1438 1500 768 773 778 900 81000
>    flags: nhsync, nvsync; type: preferred, driver
> 
> ...and, at least on ChromeOS, the userspace was consistently picking
> the first mode even though both were marked as "preferred". Now that
> the Linux driver is fixed we only get the hardcoded mode. That means
> we end up trying to drive a 1920x1080 panel at 1366x768 and it doesn't
> work so well.
> 
> Let's switch over to the generic panel-edp.
> 
> Fixes: fb3f43d50d9b ("drm/panel-edp: Avoid adding multiple preferred modes")
> Signed-off-by: Douglas Anderson <dianders@chromium.org>
> ---
Acked-by: Konrad Dybcio <konrad.dybcio@linaro.org>

Konrad