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

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Message-ID: <a50eb87a-4dcc-4272-b897-fb8170bfe58b@linaro.org>
Date: Thu, 4 Jul 2024 18:41:21 +0200
From: Daniel Lezcano <daniel.lezcano@...aro.org>
To: Neil Armstrong <neil.armstrong@...aro.org>,
 Sebastian Reichel <sre@...nel.org>, Krzysztof Kozlowski <krzk@...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 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 ?

> Link: https://lore.kernel.org/all/2ed4c630-204a-4f80-a37f-f2ca838eb455@linaro.org/
> Fixes: 5bc28b93a36e ("power_supply: power_supply_read_temp only if use_cnt > 0")
> Fixes: 3be330bf8860 ("power_supply: Register battery as a thermal zone")
> Signed-off-by: Neil Armstrong <neil.armstrong@...aro.org>
> ---
>   drivers/power/supply/power_supply_core.c | 7 ++++++-
>   1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/power/supply/power_supply_core.c b/drivers/power/supply/power_supply_core.c
> index 8f6025acd10a..b38bff4dbfc7 100644
> --- a/drivers/power/supply/power_supply_core.c
> +++ b/drivers/power/supply/power_supply_core.c
> @@ -1287,8 +1287,13 @@ static int power_supply_read_temp(struct thermal_zone_device *tzd,
>   	WARN_ON(tzd == NULL);
>   	psy = thermal_zone_device_priv(tzd);
>   	ret = power_supply_get_property(psy, POWER_SUPPLY_PROP_TEMP, &val);
> +	/*
> +	 * The thermal core expects -EAGAIN as non-fatal error,
> +	 * convert -ENODEV as -EAGAIN since -ENODEV is returned
> +	 * when a power supply device isn't initialized
> +	 */
>   	if (ret)
> -		return ret;
> +		return ret == -ENODEV ? -EAGAIN : ret;
>   
>   	/* Convert tenths of degree Celsius to milli degree Celsius. */
>   	*temp = val.intval * 100;
> 
> ---
> base-commit: 82e4255305c554b0bb18b7ccf2db86041b4c8b6e
> change-id: 20240704-topic-sm8x50-upstream-fix-battmgr-temp-tz-warn-077166861efb
> 
> Best regards,

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