Re: [PATCH 3/5] arm64: dts: qcom: sc7180: Start the trogdor eDP/touchscreen regulator on

[Matthias Kaehlcke]

On Thu, Dec 08, 2022 at 11:20:04AM -0800, Douglas Anderson wrote:
> Now that we've added the `off-on-delay-us` for the touchpanel
> regulator, we can see that we're actually hitting that delay at
> bootup. I saw about 200 ms of delay.
> 
> Let's avoid that delay by starting the regulator on. We'll only do
> this for eDP devices for the time being.
> 
> NOTE: we _won't_ do this for homestar. Homestar's panel really likes
> to be power cycled. It's why the Linux driver for this panel has a
> pm_runtime_put_sync_suspend() when the panel is being unprepared but
> the normal panel-edp driver doesn't. It's also why this hardware has a
> separate power rail for eDP vs. touchscreen, unlike all the other
> trogdor boards. We won't start homestar's regulator on. While this
> could mean a slight delay on homestar, it is probably a _correct_
> delay. The bootloader might have left the regulator on (it does so in
> dev and recovery modes), so if we turned the regulator off at probe
> time and we actually hit the delay then we were probably violating T12
> in the panel spec.
> 
> Signed-off-by: Douglas Anderson <dianders@xxxxxxxxxxxx>

Reviewed-by: Matthias Kaehlcke <mka@xxxxxxxxxxxx>