Re: [PATCH 1/7] ARM: dts: imx: keep the SY7636A VCOM on

[Alistair <alistair@alistair23.me>]

On Mon, 2026-10-26 at 08:30 +0100, Andreas Kemnade wrote:
> On Mon, 26 Oct 2026 00:39:12 +0000
> Pablo Mazzini <pmazzini@gmail.com> wrote:
> 
> > The SY7636A hwmon driver turns VCOM on at probe. The reMarkable 2,
> > Kobo
> > Libra H2O and Tolino Vision 5 have had the rails on so far. Mark
> > VCOM
> > always-on before the driver stops doing it.
> > 
> > Signed-off-by: Pablo Mazzini <pmazzini@gmail.com>
> > ---
> >  arch/arm/boot/dts/nxp/imx/e70k02.dtsi           | 1 +
> >  arch/arm/boot/dts/nxp/imx/imx7d-remarkable2.dts | 1 +
> >  2 files changed, 2 insertions(+)
> > 
> > diff --git a/arch/arm/boot/dts/nxp/imx/e70k02.dtsi
> > b/arch/arm/boot/dts/nxp/imx/e70k02.dtsi
> > index dc7ff108aa85..bd9c6c6fa117 100644
> > --- a/arch/arm/boot/dts/nxp/imx/e70k02.dtsi
> > +++ b/arch/arm/boot/dts/nxp/imx/e70k02.dtsi
> > @@ -154,6 +154,7 @@ sy7636: pmic@62 {
> >  		regulators {
> >  			reg_epdpmic: vcom {
> >  				regulator-name = "vcom";
> > +				regulator-always-on;
> >  			};
> >  		};
> >  	};
> No, please not. That regulator is in practice used with a not yet
> upstreamed
> driver for the EPDC on that platform used to deal with the current
> kernels
> fp9931 / tps65185 drivers. So it is very welcome to have it not
> always turned
> on.
> 
> 
> > diff --git a/arch/arm/boot/dts/nxp/imx/imx7d-remarkable2.dts
> > b/arch/arm/boot/dts/nxp/imx/imx7d-remarkable2.dts
> > index ff9d50942884..6cf5603c0752 100644
> > --- a/arch/arm/boot/dts/nxp/imx/imx7d-remarkable2.dts
> > +++ b/arch/arm/boot/dts/nxp/imx/imx7d-remarkable2.dts
> > @@ -327,6 +327,7 @@ sy7636a: pmic@62 {
> >  		regulators {
> >  			reg_epdpmic: vcom {
> >  				regulator-name = "vcom";
> > +				regulator-always-on;
> >  				regulator-boot-on;
> >  			};
> >  		};
> 
> 
> Here the situation is a bit different. If I remember correctly, there
> is some special EPD logic in userspace on top of some ordinary kernel
> display driver. But thesse things are missing is devicetree?! But

Yeah, the kernel just exposes a framebuffer and a special secret sauce
userspace program writes to that.

> that might need to learn to deal with regulator enabling/disabling.
> 
> Regulator always on is probably not desired here, either.

Yeah, I **think** we don't need that

Alistair

> 
> Regards,
> Andreas