linux-kernel - Re: [PATCH] arm64: dts: qcom: pm6350: add temp sensor and thermal zone config

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Message-Id: <CNQTKQWNZIH9.61TJWGH1K44F@otso>
Date:   Thu, 20 Oct 2022 16:28:07 +0200
From:   "Luca Weiss" <luca.weiss@...rphone.com>
To:     "Matthias Kaehlcke" <mka@...omium.org>
Cc:     "Krzysztof Kozlowski" <krzysztof.kozlowski@...aro.org>,
        <linux-arm-msm@...r.kernel.org>,
        <~postmarketos/upstreaming@...ts.sr.ht>,
        <phone-devel@...r.kernel.org>, "Andy Gross" <agross@...nel.org>,
        "Bjorn Andersson" <bjorn.andersson@...aro.org>,
        "Konrad Dybcio" <konrad.dybcio@...ainline.org>,
        "Rob Herring" <robh+dt@...nel.org>,
        "Krzysztof Kozlowski" <krzysztof.kozlowski+dt@...aro.org>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] arm64: dts: qcom: pm6350: add temp sensor and thermal
 zone config

Hi Matthias,

sorry for the delay in getting back to you.

On Fri Aug 12, 2022 at 6:49 PM CEST, Matthias Kaehlcke wrote:
> On Fri, Aug 12, 2022 at 04:06:47PM +0200, Luca Weiss wrote:
> > Hi Krzysztof,
> > 
> > +CC Matthias Kaehlcke (author of patch mentioned further below)
> > 
> > On Fri Aug 12, 2022 at 3:36 PM CEST, Krzysztof Kozlowski wrote:
> > > On 12/08/2022 14:44, Luca Weiss wrote:
> > > > Add temp-alarm device tree node and a default configuration for the
> > > > corresponding thermal zone for this PMIC. Temperatures are based on
> > > > downstream values.
> > > > 
> > > > Signed-off-by: Luca Weiss <luca.weiss@...rphone.com>
> > > > ---
> > > > With this config I'm getting this in dmesg, not sure if it's a warning
> > > > that should be solved or just an informative warning.
> > > > 
> > > > [    0.268256] spmi-temp-alarm c440000.spmi:pmic@0:temp-alarm@...0: No ADC is configured and critical temperature is above the maximum stage 2 threshold of 140 C! Configuring stage 2 shutdown at 140 C.
> > > > 
> > > > As far as I can tell, based on downstream dts this PMIC doesn't have an
> > > > ADC.
>
> I don't seem to have access to the datasheet, in any case that the ADC isn't
> configured in the downstream dts doesn't necessarily mean the PMIC doesn't
> have one. The PM6150 has one, and it is probably relatively close to the
> PM6350.

Too bad :(

>
> > > You configure 145 and driver believes 140 is the limit, so it seems
> > > warning should be addressed.
> > 
> > Hm...
> > 
> > >
> > > From where did you get 145 degrees as limit? Downstream DTS?
> > 
> > Yes, downstream dts[0].
> > 
> > From what I can see in the downstream driver, it always disabled this
> > "software override of stage 2 and 3 shutdowns"[1]
> > 
> > In mainline only since f1599f9e4cd6 ("thermal: qcom-spmi: Use PMIC
> > thermal stage 2 for critical trip points") this check exists, which is
> > not part of downstream (wasn't in 4.19 yet), where this software
> > override tries to get enabled so that thermal core can handle this.
> > 
> > Any suggestion what I can do here? Maybe looking at msm-5.4 sources (and
> > associated dts) might reveal something..?
>
> I wouldn't necessarily consider QC downstream code as a reliable source of
> truth ...
>
> > Maybe newer SoCs/PMICs have a different config?
>
> Commit aa92b3310c55 ("thermal/drivers/qcom-spmi-temp-alarm: Add support
> for GEN2 rev 1 PMIC peripherals") added support for gen2 PMICs, which
> actually have lower thresholds than gen1. From the log it seems that the
> PM6350 is identified as gen1 device (max stage 2 threshold = 140 degC).

PM6350 is detected as QPNP_TM_SUBTYPE_GEN2 so gen2 actually. Just the
log message is hardcoded to 140 degC, the if above actually has
stage2_threshold_max = 125000 (125degC) and stage2_threshold_min =
110000 (110degC) so lower than 140 (basically like you said).

>
> It seems setting the limit to 140 degC or one of the other stage 2
> thresholds would be a reasonable course of action. stage 2 is the
> threshold at which the PMIC is so hot that the system should shut
> down, and 140 degC is the highest of the stage 2 thresholds. Even
> if it was possible, what would be gained from setting the trip
> point 5 degC higher?

Based on this, do you think it's reasonable to just set the limit to
125 degC and be done with it? Or some other way to resolve this? I'd of
course mention in the commit message that I've decreased the value from
145 (msm-4.19) to 125.

Regards
Luca