linux-kernel - Re: [PATCH v2] drivers: thermal: tsens: respect thermal_device

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Date:   Thu, 20 Jan 2022 17:10:30 +0530
From:   Amit Kucheria <amitk@...nel.org>
To:     Benjamin Li <benl@...areup.com>
Cc:     Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Zhang Rui <rui.zhang@...el.com>,
        Linux PM list <linux-pm@...r.kernel.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] drivers: thermal: tsens: respect thermal_device_mode
 in threshold irq reporting

On Fri, Jan 14, 2022 at 8:47 AM Benjamin Li <benl@...areup.com> wrote:
>
> 'echo disabled > .../thermal_zoneX/mode' will disable the thermal core's
> polling mechanism to check for threshold trips. This is used sometimes to
> run performance test cases.
>
> However, tsens supports an interrupt mechanism to receive notification of
> trips, implemented in commit 634e11d5b450 ("drivers: thermal: tsens: Add
> interrupt support").
>
> Currently the thermal zone mode that's set by userspace is not checked
> before propagating threshold trip events from IRQs. Let's fix this to
> restore the abilty to disable thermal throttling at runtime.
>
> ====================
>
> Tested on MSM8939 running 5.16.0. This platform has 8 cores; the first
> four thermal zones control cpu0-3 and the last zone is for the other four
> CPUs together.
>
>   for f in /sys/class/thermal/thermal_zone*; do
>     echo "disabled" > $f/mode
>     echo $f | paste - $f/type $f/mode
>   done
>
> /sys/class/thermal/thermal_zone0        cpu0-thermal    disabled
> /sys/class/thermal/thermal_zone1        cpu1-thermal    disabled
> /sys/class/thermal/thermal_zone2        cpu2-thermal    disabled
> /sys/class/thermal/thermal_zone3        cpu3-thermal    disabled
> /sys/class/thermal/thermal_zone4        cpu4567-thermal disabled
>
> With mitigation thresholds at 75 degC and load running, we can now cruise
> past temp=75000 without CPU throttling kicking in.
>
>   watch -n 1 "grep '' /sys/class/thermal/*/temp
>       /sys/class/thermal/*/cur_state
>       /sys/bus/cpu/devices/cpu*/cpufreq/cpuinfo_cur_freq"
>
> /sys/class/thermal/thermal_zone0/temp:82000
> /sys/class/thermal/thermal_zone1/temp:84000
> /sys/class/thermal/thermal_zone2/temp:87000
> /sys/class/thermal/thermal_zone3/temp:84000
> /sys/class/thermal/thermal_zone4/temp:84000
> /sys/class/thermal/cooling_device0/cur_state:0
> /sys/class/thermal/cooling_device1/cur_state:0
> /sys/bus/cpu/devices/cpu0/cpufreq/cpuinfo_cur_freq:1113600
> /sys/bus/cpu/devices/cpu1/cpufreq/cpuinfo_cur_freq:1113600
> /sys/bus/cpu/devices/cpu2/cpufreq/cpuinfo_cur_freq:1113600
> /sys/bus/cpu/devices/cpu3/cpufreq/cpuinfo_cur_freq:1113600
> /sys/bus/cpu/devices/cpu4/cpufreq/cpuinfo_cur_freq:800000
> /sys/bus/cpu/devices/cpu5/cpufreq/cpuinfo_cur_freq:800000
> /sys/bus/cpu/devices/cpu6/cpufreq/cpuinfo_cur_freq:800000
> /sys/bus/cpu/devices/cpu7/cpufreq/cpuinfo_cur_freq:800000
>
> Reported-by: Zac Crosby <zac@...areup.com>
> Signed-off-by: Benjamin Li <benl@...areup.com>
> ---
> Changes in v2:
> - Reordered sentences in first part of commit message to make sense.
>
>  drivers/thermal/qcom/tsens.c | 15 +++++++++------
>  1 file changed, 9 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/thermal/qcom/tsens.c b/drivers/thermal/qcom/tsens.c
> index 99a8d9f3e03c..0b6299512e7c 100644
> --- a/drivers/thermal/qcom/tsens.c
> +++ b/drivers/thermal/qcom/tsens.c
> @@ -509,13 +509,16 @@ static irqreturn_t tsens_irq_thread(int irq, void *data)
>                 spin_unlock_irqrestore(&priv->ul_lock, flags);
>
>                 if (trigger) {
> -                       dev_dbg(priv->dev, "[%u] %s: TZ update trigger (%d mC)\n",
> -                               hw_id, __func__, temp);
> -                       thermal_zone_device_update(s->tzd,
> -                                                  THERMAL_EVENT_UNSPECIFIED);
> +                       if (s->tzd->mode == THERMAL_DEVICE_ENABLED) {
> +                               dev_dbg(priv->dev, "[%u] %s: TZ update trigger (%d mC)\n",
> +                                       hw_id, __func__, temp);
> +                               thermal_zone_device_update(s->tzd, THERMAL_EVENT_UNSPECIFIED);
> +                       } else {
> +                               dev_dbg(priv->dev, "[%u] %s: TZ update trigger (%d mC) skipped as zone disabled\n",

Hmm. I don't like the fact that these messages won't be visible to
users in dmesg unless they're debugging. This change puts the SoC in a
potentially unsafe state. Perhaps we should print a ratelimited
message in the logs that we're operating outside safety limits?

> +                                       hw_id, __func__, temp);
> +                       }
>                 } else {
> -                       dev_dbg(priv->dev, "[%u] %s: no violation:  %d\n",
> -                               hw_id, __func__, temp);
> +                       dev_dbg(priv->dev, "[%u] %s: no violation:  %d\n", hw_id, __func__, temp);

Get rid of this hunk, it is unrelated to the above change.

>                 }
>
>                 if (tsens_version(priv) < VER_0_1) {
> --
> 2.17.1
>