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

[Andreas Kemnade]

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