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

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Message-Id: <20240704-topic-sm8x50-upstream-fix-battmgr-temp-tz-warn-v1-1-9d66d6f6efde@linaro.org>
Date: Thu, 04 Jul 2024 10:52:08 +0200
From: Neil Armstrong <neil.armstrong@...aro.org>
To: 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: Daniel Lezcano <daniel.lezcano@...aro.org>, 
 "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, Neil Armstrong <neil.armstrong@...aro.org>
Subject: [PATCH] power: supply: core: return -EAGAIN on uninitialized read
 temp

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.

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,
-- 
Neil Armstrong <neil.armstrong@...aro.org>