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

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Date:   Wed, 10 Feb 2021 13:51:16 +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,

On Mon, 8 Feb 2021 at 20:11, Konrad Dybcio <konrad.dybcio@...ainline.org> wrote:
>
>
> >>> +      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?
>
> sdm845.dtsi, L4139 as of v5.11-rc7:
>
>
> port@1 {
>                         reg = <1>;
>                         dsi0_out: endpoint {
>                         };
>                     };
>
>
> This means you can essentially do:
>
> &dsi0_out {
>
>     remote-endpoint = <&tianma_nt36672a_in_0>;
>     lanes = <0 1 2 3>;
>
> };
>
>
> in your dt :)
>

Thank you. Added in v3.

>
> >>> +              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
> >
> I understand your concerns, however we actually did find out that at least one device had LAB/IBB set up by the bootloader in a way that could potentially damage the electronics, so I'm just making you aware. If it works as-is, it's probably OK.

Device seem to be booting fine with downstream labibb regulator node
changes, hence added them in v3 as well. Smoke tested on
5.11.0-rc7-next-20210209.

Regards,
Amit Pundir

>
>
> Konrad
>