Re: [PATCH 4/4] arm64: dts: qcom: x1e80100-dell-xps13-9345: introduce EC

[Aleksandrs Vinarskis]

On Wednesday, April 1st, 2026 at 11:21, Konrad Dybcio <konrad.dybcio@xxxxxxxxxxxxxxxx> wrote:

> On 4/1/26 9:33 AM, Aleksandrs Vinarskis wrote:
> > Describe embedded controller, its interrupt and required thermal zones.
> > Add EC's reset GPIO to reserved range, as triggering it during device
> > operation leads to unrecoverable and unusable state.
> >
> > Signed-off-by: Aleksandrs Vinarskis <alex@xxxxxxxxxxxxx>
> > ---
>
> [...]
>
> > +		io-channels = <&pmk8550_vadc PM8350_ADC7_GPIO3_100K_PU(1)>,
> > +			      <&pmk8550_vadc PM8350_ADC7_GPIO4_100K_PU(1)>,
> > +			      <&pmk8550_vadc PM8350_ADC7_AMUX_THM1_100K_PU(1)>,
> > +			      <&pmk8550_vadc PM8350_ADC7_AMUX_THM2_100K_PU(1)>,
> > +			      <&pmk8550_vadc PM8350_ADC7_AMUX_THM3_100K_PU(1)>,
> > +			      <&pmk8550_vadc PM8350_ADC7_AMUX_THM4_100K_PU(1)>,
> > +			      <&pmk8550_vadc PM8350_ADC7_AMUX_THM5_100K_PU(1)>;
> > +
> > +		io-channel-names = "sys_therm0", "sys_therm1", "sys_therm2",
> > +				   "sys_therm3", "sys_therm4", "sys_therm5",
> > +				   "sys_therm6";
>
> nit: one a line please, without a separating \n between x and x-names

Will drop \n. One a line as in:
io-channel-names = "sys_therm0",
                   "sys_therm1",
                   "sys_therm2",
                    ...
?

>
> [...]
>
> > +&pmk8550_vadc {
> > +	/* sys_therm0, around DRAM */
>
> another nit: I think repeating the name set in the label in each comment
> is a little excessive

Will drop,

>
> [...]
>
> >  &tlmm {
> >  	gpio-reserved-ranges = <44 4>,  /* SPI11 (TPM) */
> > +			       <65 1>,  /* EC Reset */
>
> Is that a "this may not be accessed" or rather "you can, but it has dire
> consequences"?

The latter. Triggering EC reset appears to leave it in un-initialized state.
When analyzing i2c dumps I noticed UEFI sends some data to EC prior to
Windows driver loading, I am assuming its required for EC configuration.
When resetting EC from userpsace:
- Keyboard, Trackpad, touch-row power is out. WiFi connection drops. Dell's
  UEFI allows disabling many peripherals, EC can 'veto' their resets and/or
  power supplies. It appears in default reset state it kill some/all outputs
- Holding power button does not reboot laptop, it looks as if it asserts and
  holds EC in reset until released. During this time fans spin to max speed.
- Device can be recovered only by disassembly and battery removal.

>
> Would the EC driver/binding benefit from having a reference to that pin?

It will not be used by the driver, and it would greatly inconvenience user
if triggered manually. I would make the reset pin as inaccessible as
possible, but if you say its cleaner to reference it to EC driver and just
not use it, I could do that as well.

Thanks for fast review,
Alex  

>
> Konrad
>