Re: [PATCH v6 3/3] arm64: dts: qcom: x1e80100-dell-xps13-9345: introduce EC

[Liviu Nicoara <lnicoara@thinkoid.org>]

On Thu, 22 Oct 2026 17:07:25 +0000, Aleksandrs Vinarskis wrote:
> I do not think the left charger you identified is correct - how did
> you arrive to that conclusion? Curious to compare to my method.

I am afraid my method was simpler and coarser than yours: one run per
port, nineteen samples ten seconds apart, the charger feeding the
system only (battery at 96 % and not charging), on a 7.2.6 kernel
with all four GPIO channels in one DTB. The deltas over three minutes:

Channel                Left charger   Right charger
0x14b  AMUX2_GPIO          +1.6           -0.9
0x145  AMUX2_THM           +0.1           +3.4
0x146  AMUX3_THM           +0.8           -0.1
0x14a  AMUX1_GPIO          -0.2           +1.3
0x144  AMUX1_THM           -0.1           +0.2
0x148  AMUX5_THM           -0.2           +1.2
0x147  AMUX4_THM           +0.1           +1.8
0x14d  AMUX4_GPIO          +0.0           -0.0

The other channels fell or held while 0x14b rose, so it was not the
board warming as a whole. But 1.6 C in three minutes, against your
2.3 C in ten seconds on the right, might mean that 0x14b is a sensor
somewhere on the left side of the board, not necessarily on the left
port's power path. Under SSD load it moved with 0x146 and fell with
it in cool-down, which puts it close to the SSD. "Left charger" was
my reading of the sign pattern. Your ten-second test is probably the
better discriminator for a sensor on a power path. If nothing answers
the left charger in ten seconds, the simpler reading is that the left
port has no thermistor of its own among these seven.

> pm8550_gpio_02 does NOT clearly follow. In your test you have
> waited multiple minutes, which is enough to heat up a larger
> area on the motherboard.

Agreed. In your left run it was the only channel with a positive
delta while the board drifted down, which is the same weak signal I
had, and no more than that.

On the two AMUX3/AMUX4 GPIO channels: neither carries a thermistor
on this unit, and your tables say the same for yours. 0x14c reads
130.048 C on every sample, the last row of the conversion table,
where the driver clamps a voltage at or below the lowest it knows.
Its input sits near 0 V. Windows' ADC configuration sets up only
PM8550 GPIO3 and GPIO4 as analog inputs, for AMUX1 and AMUX2, so the
pin behind AMUX3 is in its digital default, and PM8550's low GPIOs
read back here as inputs with a 10 uA pull-down. 0x14d held 34.7 C
within 0.1 C through both chargers and two load runs on this unit,
and 35.8 to 36.0 C through every one of your tests, the hairdryer
included. That is a biased pin, not a sensor. Both nodes can go.

> ADC5_GEN3_AMUX1_GPIO_100K_PU - Likely "lpddr5_therm"

I cannot separate 0x14a from 0x144 and 0x148 by heating. Under a
one-core load reading a file from /dev/shm they rose 14.0, 14.4 and
14.2 C in lockstep, while the SoC's mem TSENS zone rose 20 C. Your
RAM stress warmed every PMIC die by 1 to 4 C as well, so it does not
single out 0x14a either. The three sit with the SoC; which one is the
memory I cannot tell.

> Looks more like "sys_therm5" is the actual keyboard thermistor.

Consistent with what I see. 0x147 is the coolest of the seven, 29 C
at idle, and nearly indifferent to board loads: it gained 2.0 C where
0x144 gained 9.2 under SSD I/O, and 2.5 C where 0x144 gained 14.4
under the CPU load. A sensor away from the board, on the skin side,
fits.

On 0x146: under four minutes of direct-I/O reads it rose 8.2 C
against 10.0 C on the NVMe's own sensor, the largest share of any
channel, and it fell at once when the load stopped while the
SoC-side channels kept rising. Under the CPU-only control its share
halved. I would keep "ssd_conn_therm" on it with partial confidence,
but I will not argue if it goes with the others.

> Alternatively, I am leaning to drop the labels for anything we are
> not sure about...

Or just give them pirate names. Jk.

Agreed. 0x145 as the right charger is what both of us measured.
Everything else is a guess until the teardown. Numbering sys_therm
from 1 matches Windows' SYS_THERM1 to 7, so that helps too.

One consequence on my side: the 9345 thermal-zones patch
(20261006185557.23016-1-lnicoara@thinkoid.org) names its zones
chg-left on 0x14b and ssd on 0x146. I will respin it with neutral
names for the zones that are not settled, so the two patches agree.

Happy to test a v7, including a lid close on the EC interrupt line,
which my v6 run did not cover.

I love this laptop, but I will not open it up just to pinpoint the
right thermistors' locations.

Liviu