linux-kernel - Re: [PATCH v2] thermal: core: Call monitor_thermal

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Message-ID: <CAJZ5v0jiCgPKRha81NyUChNVGe02+GDNX442NsZL=XDPao_4WA@mail.gmail.com>
Date: Wed, 3 Jul 2024 18:08:47 +0200
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Daniel Lezcano <daniel.lezcano@...aro.org>
Cc: neil.armstrong@...aro.org, "Rafael J. Wysocki" <rjw@...ysocki.net>, 
	Linux PM <linux-pm@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>, 
	Lukasz Luba <lukasz.luba@....com>, 
	Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>, Zhang Rui <rui.zhang@...el.com>, 
	linux-arm-msm <linux-arm-msm@...r.kernel.org>
Subject: Re: [PATCH v2] thermal: core: Call monitor_thermal_zone() if zone
 temperature is invalid

On Wed, Jul 3, 2024 at 4:00 PM Daniel Lezcano <daniel.lezcano@...aro.org> wrote:
>
> On 03/07/2024 14:43, neil.armstrong@...aro.org wrote:
> > Hi,
> >
> > On 03/07/2024 14:25, Daniel Lezcano wrote:
> >>
> >> Hi Neil,
> >>
> >> it seems there is something wrong with the driver actually.
> >>
> >> There can be a moment where the sensor is not yet initialized for
> >> different reason, so reading the temperature fails. The routine will
> >> just retry until the sensor gets ready.
> >>
> >> Having these errors seem to me that the sensor for this specific
> >> thermal zone is never ready which may be the root cause of your issue.
> >> The change is spotting this problem IMO.
> >
> > Probably, but it gets printed every second until system shutdown, but
> > only for a single thermal_zone.
> >
> > Using v1 of Rafael's patch makes the message disappear completely.
>
> Yes, because you have probably the thermal zone polling delay set to
> zero, thus it fails the first time and does no longer try to set it up
> again. The V1 is an incomplete fix.
>
> Very likely the problem is in the sensor platform driver, or in the
> thermal zone description in the device tree which describes a non
> functional thermal zone.

I agree, but polling this useless thermal zone forever is not
particularly useful.

I was kind of afraid that something like this would happen, but then I
didn't want to complicate the patch unnecessarily until I knew that it
really would happen.

So attached is a modification of the $subject patch that will double
the temperature recheck delay after every failed attempt to get the
zone temperature and it will give up eventually (in this particular
version, after the recheck delay exceeds 30 s).

I would appreciate giving it a go (obviously, by replacing the
$subject one with it).

View attachment "thermal-poll-if-temp-invalid-v3.patch" of type "text/x-patch" (5036 bytes)