linux-kernel - Re: [PATCH v3 2/2] arm64: dts: qcom: pm8998: Add pm8998 thermal zone

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Date:   Thu, 12 Jul 2018 11:39:47 -0700
From:   Doug Anderson <dianders@...omium.org>
To:     Matthias Kaehlcke <mka@...omium.org>
Cc:     Andy Gross <andy.gross@...aro.org>,
        David Brown <david.brown@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        "open list:ARM/QUALCOMM SUPPORT" <linux-soc@...r.kernel.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        David Collins <collinsd@...eaurora.org>,
        Stephen Boyd <sboyd@...nel.org>
Subject: Re: [PATCH v3 2/2] arm64: dts: qcom: pm8998: Add pm8998 thermal zone

Hi,

On Mon, Jul 9, 2018 at 2:25 PM, Matthias Kaehlcke <mka@...omium.org> wrote:
> The thermal zone uses spmi-temp-alarm as sensor. If the sensor is
> configured without an IIO input it always reports 37°C for temperatures
> below the first hardware trip point at 105°C. This hardware trip point
> is configured as critical trip point, to initiate a system shutdown
> before the temperature reaches the next hardware trip point at 125°C,
> where the PMIC performs a partial shutdown.
>
> The temperature of the critical trip point can be increased after
> adding the die temperature ADC as IIO input for spmi-temp-alarm, which
> significantly increases the precision of the temperature measurements.
>
> Signed-off-by: Matthias Kaehlcke <mka@...omium.org>
> ---
> Changes in v3:
> - moved 'thermal-zones' node to the beginning of the .dtsi
>
> Changes in v2:
> - defined 'thermal-zones' node in pm8998.dtsi instead of using a label
>   to refer to it
> - use 105°C hardware trip point as critical trip point
> - reduced number of trip points to 2
> - lowered temperature of passive trip point
> - updated trip point names and added labels
> - updated commit message
> ---
>  arch/arm64/boot/dts/qcom/pm8998.dtsi | 25 +++++++++++++++++++++++++
>  1 file changed, 25 insertions(+)
>
> diff --git a/arch/arm64/boot/dts/qcom/pm8998.dtsi b/arch/arm64/boot/dts/qcom/pm8998.dtsi
> index 7eea94701b23..52c5e797aab2 100644
> --- a/arch/arm64/boot/dts/qcom/pm8998.dtsi
> +++ b/arch/arm64/boot/dts/qcom/pm8998.dtsi
> @@ -3,6 +3,31 @@
>
>  #include <dt-bindings/spmi/spmi.h>
>  #include <dt-bindings/interrupt-controller/irq.h>
> +#include <dt-bindings/thermal/thermal.h>
> +
> +/ {
> +       thermal-zones {
> +               pm8998 {
> +                       polling-delay-passive = <250>;
> +                       polling-delay = <1000>;
> +
> +                       thermal-sensors = <&pm8998_temp>;
> +
> +                       trips {
> +                               pm8998_alert0: pm8998-alert0 {
> +                                       temperature = <95000>;
> +                                       hysteresis = <2000>;
> +                                       type = "passive";
> +                               };
> +                               pm8998_crit: pm8998-crit {
> +                                       temperature = <105000>;
> +                                       hysteresis = <2000>;
> +                                       type = "critical";
> +                               };

IMHO since the 95000 won't trigger until we get the ADC, it's a bit
too extreme to go straight to shutdown when the PMIC reaches 105.  I
think we should take David Collins's advice and disable the "partial
PMIC shutdown" and then set the two stages to 105 (passive) / 125
(critical).  In theory we could add a 115 (hot) stage in there that
would only get triggered later when the ADC gets hooked up.

Personally I wouldn't land this patch until we do that.

-Doug