Re: [PATCH] arm64: dts: qcom: sdm845-oneplus: add panel rails to simplefb

[Sam Day]

Hey Konrad,

On Tuesday, 30 June 2026 at 12:24 AM, Konrad Dybcio <konrad.dybcio@xxxxxxxxxxxxxxxx> wrote:

> On 6/20/26 1:15 AM, Sam Day wrote:
> > Hello Konrad,
> >
> > On Saturday, 20 June 2026 at 1:11 AM, Konrad Dybcio <konrad.dybcio@xxxxxxxxxxxxxxxx> wrote:
> >
> >> On 6/16/26 7:27 AM, Sam Day via B4 Relay wrote:
> >>> From: Sam Day <me@xxxxxxxxxxx>
> >>>
> >>> These regulators are marked regulator-boot-on, but that doesn't
> >>> guarantee they'll stay alive as long as the simplefb does. Adding the
> >>> explicit supplies ensures that booting with MDSS disabled doesn't
> >>> switch the panel off 30 seconds after boot.
> >>
> >> Why would you boot without MDSS if you want the panel to function?
> >
> > For my particular use-case [1] I'm trying to avoid taking over the display
> > hardware entirely, and use simplefb until kexecing into the real kernel. In
> > this case the user might halt in a pre-boot menu UI for a while.
> >
> > I can also imagine this being similarly useful for "recovery kernel" use-cases
> > where again, it may not be desirable to assume control of MDSS/MDP/DSI blocks.
> >
> > [1]: https://github.com/samcday/pocketboot
> 
> Can you handle this by adding a panel = <&display_panel> property
> under simplefb, pointing to the display panel defined in the same
> file?

No, that won't work because display_panel is a child of mdss_dsi0, which is
a child of mdss. So if those nodes are disabled (which is what I'm trying to
achieve), fw_devlink will defer probing simplefb.

BR,
-Sam

> 
> Konrad
>