Re: [PATCH 4/4] arm64: dts: qcom: qcm6490-fairphone-fp5: Add PM7325 thermals

["Luca Weiss" <luca.weiss@fairphone.com>]

On Wed Oct 18, 2023 at 10:28 PM CEST, Konrad Dybcio wrote:
>
>
> On 10/14/23 19:52, Luca Weiss wrote:
> > On Samstag, 14. Oktober 2023 01:13:29 CEST Konrad Dybcio wrote:
> >> On 13.10.2023 10:09, Luca Weiss wrote:
> >>> Configure the thermals for the QUIET_THERM, CAM_FLASH_THERM, MSM_THERM
> >>> and RFC_CAM_THERM thermistors connected to PM7325.
> >>>
> >>> With this PMIC the software communication to the ADC is going through
> >>> PMK7325 (= PMK8350).
> >>>
> >>> Signed-off-by: Luca Weiss <luca.weiss@fairphone.com>
> >>> ---
> >>>
> >>>   arch/arm64/boot/dts/qcom/qcm6490-fairphone-fp5.dts | 117
> >>>   +++++++++++++++++++++ 1 file changed, 117 insertions(+)
> >>>
> >>> diff --git a/arch/arm64/boot/dts/qcom/qcm6490-fairphone-fp5.dts
> >>> b/arch/arm64/boot/dts/qcom/qcm6490-fairphone-fp5.dts index
> >>> 2c01f799a6b2..d0b1e4e507ff 100644
> >>> --- a/arch/arm64/boot/dts/qcom/qcm6490-fairphone-fp5.dts
> >>> +++ b/arch/arm64/boot/dts/qcom/qcm6490-fairphone-fp5.dts
> >>> @@ -9,6 +9,7 @@
> >>>
> >>>   #define PM7250B_SID 8
> >>>   #define PM7250B_SID1 9
> >>>
> >>> +#include <dt-bindings/iio/qcom,spmi-adc7-pm7325.h>
> >>>
> >>>   #include <dt-bindings/iio/qcom,spmi-adc7-pmk8350.h>
> >>>   #include <dt-bindings/leds/common.h>
> >>>   #include <dt-bindings/pinctrl/qcom,pmic-gpio.h>
> >>>
> >>> @@ -137,6 +138,20 @@ afvdd_2p8: regulator-afvdd-2p8 {
> >>>
> >>>   	};
> >>>   	
> >>>   	thermal-zones {
> >>>
> >>> +		camera-thermal {
> >>> +			polling-delay-passive = <0>;
> >>> +			polling-delay = <0>;
> >>> +			thermal-sensors = <&pmk8350_adc_tm 2>;
> >>> +
> >>> +			trips {
> >>> +				active-config0 {
> >>> +					temperature = <125000>;
> >>
> >> are
> >>
> >>> +		rear-cam-thermal {
> >>>
> >>> +					temperature = <125000>;
> >>
> >> you
> >>
> >>> +		sdm-skin-thermal {
> >>>
> >>> +					temperature = <125000>;
> >>
> >> sure
> >>
> >> about these temps?
> > 
> > (email from my other address, quicker right now)
> > 
> > Well yes and no.
> > 
> > Yes as in those are the temps specified in downstream dtb.
> > No as in I'm 99% sure there's user space with definitely lower threshold that
> > actually does something in response to the temps.
> > 
> > I didn't look too much into this but does the kernel even do something when it
> > hits one of these trip points? I assume when there's a cooling device thing
> > specified then it can actually tell the driver to do something, but without
> > (and most drivers don't support this?) I'm assuming the kernel can't do much
> > anyways?
> > 
> > So e.g. when the temperature for the flash led is reached I'm assuming
> > downstream (+Android) either dims the led or turns it off? But I'd have to dig
> > quite a bit into the thermal setup there to check what it's really doing.
> I think reaching "critical" shuts down the platform, unless something
> registering the thermal zone explicitly overrides the behavior.

Should probably be easy to test, especially the camera flash thermal
zone heats up *very* quickly when the flash is on, so should be trivial
to set the trip point down from 125degC to e.g. 45degC and see what
happens.

So I did this and... nothing happened.
I watched /sys/class/thermal/thermal_zone34/temp climb above 45degC and
nothing happened.

I guess trip type being "passive" and no cooling-device makes it not do
anything.

  ==> /sys/class/thermal/thermal_zone34/trip_point_0_hyst <==
  1000
  ==> /sys/class/thermal/thermal_zone34/trip_point_0_temp <==
  45000
  ==> /sys/class/thermal/thermal_zone34/trip_point_0_type <==
  passive

From Documentation/devicetree/bindings/thermal/thermal-zones.yaml:

  - active   # enable active cooling e.g. fans
  - passive  # enable passive cooling e.g. throttling cpu
  - hot      # send notification to driver
  - critical # send notification to driver, trigger shutdown

So unless we want to just shut down the system (with "critical"), I
don't think thermal can't really do anything else right now, since e.g.
leds-qcom-flash.c driver doesn't have any cooling support to lower the
brightness or turn off the LED.

So.. in essence not much we can do right now.

But seems we also cannot remove this (kinda useless) trip since we need
at least one trip point in the dts if I read the bindings yaml
correctly.

>
> > 
> > But for now I think it's okay to put this current thermal config into dts and
> > we'll improve it later when 1. I understand more and 2. maybe some useful
> > drivers support the cooling bits?
> Yeah it's better than nothing, but ultimately we should probably move
> the values that userspace daemon operates on here in the dt..

For sure.. I spent a bit of time looking into the proprietary Qualcomm
thermal-daemon sources but didn't really see much interesting things
there for this platform, maybe some of this thermal handling is
somewhere else - or half of these thermal zones aren't even used with
Android.

So.. good to get the current patch upstream or not? :)

Regards
Luca

>
> Konrad