linux-kernel - Re: [PATCH] power: supply: core: return -EAGAIN on uninitialized read temp

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Message-ID: <1c981a21-8735-4bf6-9964-233b3a742f44@linaro.org>
Date: Mon, 15 Jul 2024 11:30:27 +0200
From: Neil Armstrong <neil.armstrong@...aro.org>
To: Daniel Lezcano <daniel.lezcano@...aro.org>,
 Krzysztof Kozlowski <krzk@...nel.org>, Sebastian Reichel <sre@...nel.org>,
 Rhyland Klein <rklein@...dia.com>, Anton Vorontsov <cbouatmailru@...il.com>,
 Jenny TC <jenny.tc@...el.com>
Cc: "Rafael J. Wysocki" <rjw@...ysocki.net>, linux-arm-msm@...r.kernel.org,
 linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
 regressions@...ts.linux.dev
Subject: Re: [PATCH] power: supply: core: return -EAGAIN on uninitialized read
 temp

On 05/07/2024 10:08, Daniel Lezcano wrote:
> On 05/07/2024 07:56, Krzysztof Kozlowski wrote:
>> On 04/07/2024 18:41, Daniel Lezcano wrote:
>>> On 04/07/2024 10:52, Neil Armstrong wrote:
>>>> If the thermal core tries to update the temperature from an
>>>> uninitialized power supply, it will swawn the following warning:
>>>> thermal thermal_zoneXX: failed to read out thermal zone (-19)
>>>>
>>>> But reading from an uninitialized power supply should not be
>>>> considered as a fatal error, but the thermal core expects
>>>> the -EAGAIN error to be returned in this particular case.
>>>>
>>>> So convert -ENODEV as -EAGAIN to express the fact that reading
>>>> temperature from an uninitialized power supply shouldn't be
>>>> a fatal error, but should indicate to the thermal zone it should
>>>> retry later.
>>>>
>>>> It notably removes such messages on Qualcomm platforms using the
>>>> qcom_battmgr driver spawning warnings until the aDSP firmware
>>>> gets up and the battery manager reports valid data.
>>>
>>> Is it possible to have the aDSP firmware ready first ?
>>
>> I don't think so. ADSP firmware is a file, so as every firmware it can
>> be loaded from rootfs, not initramfs (unlike this driver), or even missing.
> 
> Ok, said differently, can't we initialize the thermal zone after the firmware is loaded ?

This is the goal, but this can't be a fix but a proper rework.

> 

I think changing power_supply_core.c is not the right solution.

qcom_battmgr_bat_get_property() should return -EAGAIN instead of
-ENODEV.

Neil