Re: [PATCH 4/7] regulator: sy7636a: wait for power good, then switch VCOM_EN

[Pablo Mazzini]

It only changes the power-off order (VCOM before the other rails instead
of all together), which made no visible difference. I will drop it in v2
and keep only the power good wait. Splitting VCOM from vposneg can come
later if someone needs it.

On Mon, Oct 26, 2026 at 8:10 AM Andreas Kemnade <andreas@xxxxxxxxxxxx> wrote:
>
> On Mon, 26 Oct 2026 00:39:15 +0000
> Pablo Mazzini <pmazzini@xxxxxxxxx> wrote:
>
> > Wait for power good on enable, as the TPS65185 and FP9931 drivers do.
> >
> which is a good idea that the consumers can relay on the regulators being
> useable when enabled.
>
> > The VCOM_EN line was requested but held low. When it is wired, let it
> > switch VCOM after power good.
> >
> What is the reason for this change? VCOM gets enabled this way, too.
> I added this line just for having the hardware completely documented.
>
> A possible scenario where I could imagine this line being useful:
>
> Calibration of required VCOM voltage, You would turn on everything else,
> do a mode 0 refresh on the EPD and measure some kickback voltage on the
> otherwise inactive VCOM line and have your calculated value for that
> regulator.
>
> To be useful, several things are needed:
> - SY7636a driver needs to model vcom as a separate regulator turning
>   on a vposneg regulator. The TPS65185 driver defines a vposneg regulator.
> - ADC input is needed. The TPS65185 provides (not implemented in the
>   driver yet) such measurement. Of course that can come from another
>   chip.
> - Some (probably userspace logic) to control all of this.
>
> Regards,
> Andreas