Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.37 as permitted sender) client-ip=23.128.96.37;
MIME-Version: 1.0
In-Reply-To: <20231213163501.1.I8c20f926d15c9ddc12e423e07df1e89db1105d93@changeid>
References: <20231213163501.1.I8c20f926d15c9ddc12e423e07df1e89db1105d93@changeid>
From:   Stephen Boyd <swboyd@chromium.org>
User-Agent: alot/0.10
Date:   Wed, 13 Dec 2023 17:06:36 -0800
Message-ID: <CAE-0n52vfejT7a9Dh177dvD7G3cCx3paB7i_xgSCi=1Z4aE9nw@mail.gmail.com>
Subject: Re: [PATCH] arm64: dts: qcom: sc7180: Switch pompom to the generic edp-panel
To:     Bjorn Andersson <andersson@kernel.org>,
        Douglas Anderson <dianders@chromium.org>
Cc:     Andy Gross <agross@kernel.org>, Conor Dooley <conor+dt@kernel.org>,
        Hsin-Yi Wang <hsinyi@chromium.org>,
        Konrad Dybcio <konrad.dybcio@linaro.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
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

Quoting Douglas Anderson (2023-12-13 16:35:02)
> 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>
> ---

Reviewed-by: Stephen Boyd <swboyd@chromium.org>