linux-kernel - Re: [PATCH v2] arm64: dts: qcom: sdm845-xiaomi-beryllium: Add DSI and panel bits

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Message-ID: <CAMi1Hd3bgDaqsH+txFVEnBc9dsGbrgic5TK7uq4GwqqkM6seiw@mail.gmail.com>
Date:   Fri, 5 Feb 2021 18:45:21 +0530
From:   Amit Pundir <amit.pundir@...aro.org>
To:     Konrad Dybcio <konrad.dybcio@...ainline.org>
Cc:     Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        John Stultz <john.stultz@...aro.org>,
        Sumit Semwal <sumit.semwal@...aro.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        dt <devicetree@...r.kernel.org>,
        lkml <linux-kernel@...r.kernel.org>, phone-devel@...r.kernel.org
Subject: Re: [PATCH v2] arm64: dts: qcom: sdm845-xiaomi-beryllium: Add DSI and
 panel bits

Hi Konrad,

On Thu, 4 Feb 2021 at 19:46, Konrad Dybcio <konrad.dybcio@...ainline.org> wrote:
>
> Hi!
>
> >vreg_l14a_1p88: ldo14 {
> >+                      regulator-min-microvolt = <1800000>;
> >+                      regulator-max-microvolt = <1800000>;
>
> Should probably be renamed to vreg_l14a_1p8 then.

ack.

>
>
> >+      ports {
> >+              port@1 {
> >+                      endpoint {
> >+                              remote-endpoint = <&tianma_nt36672a_in_0>;
> >+                              data-lanes = <0 1 2 3>;
> >+                      };
> >+              };
> >+      };
>
> The endpoint has a label, you can simply use &dsi0_out {};.

I didn't get what you meant there. Care to point to some reference dts
snippet please?

>
> >+              vddpos-supply = <&lab>;
> >+              vddneg-supply = <&ibb>;
>
> With Angelo's latest series [1] merged in, I reckon you should explicitly configure lab/ibb (like in [2]),
> as wrong settings (which CAN BE SET BY THE BOOTLOADER in some instances!!) can lead to hardware damage.

So iirc in the case of beryllium device, these regulators are pre set
by the bootloader and I can't find any reference of we
setting/resetting it explicitly to switch ON the panel and display. So
far default lab/ibb nodes are working fine for us and I'm hesitant to
tinker around anything regulator related that can potentially damage
the hardware. Having said that, I do see lab/ibb nodes being set in
the downstream dts, with relevant soft-start and discharge-resistor
properties and I can try switching to that once the new lab/ibb
changes land upstream.

Regards,
Amit Pundir


>
>
>
> Konrad
>
> [1] https://lore.kernel.org/linux-arm-msm/20210119174421.226541-1-angelogioacchino.delregno@somainline.org/
> [2] https://github.com/SoMainline/linux/commit/4f4853b2e252b5f9d03e90119110aac80258fc53