linux-kernel - [PATCH] thermal: exynos: Reduce severity of too early temperature read

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Date:   Sun, 13 May 2018 19:54:02 +0200
From:   Krzysztof Kozlowski <krzk@...nel.org>
To:     Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Zhang Rui <rui.zhang@...el.com>,
        Eduardo Valentin <edubezval@...il.com>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        linux-pm@...r.kernel.org, linux-samsung-soc@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH] thermal: exynos: Reduce severity of too early temperature read

Thermal core tries to read temperature during sensor registering in
thermal_zone_of_sensor_register().  In that time Exynos TMU driver and
hardware are not yet initialized.  Commit 0eb875d88aaa ("thermal:
exynos: Reading temperature makes sense only when TMU is turned on")
added a boolean flag to prevent reading bogus temperature in such
case but it exposed warning message during boot:
	[    3.864913] thermal thermal_zone0: failed to read out thermal zone (-22)

Return EAGAIN in such case to skip omitting such message because it
might mislead user.

Signed-off-by: Krzysztof Kozlowski <krzk@...nel.org>
---
 drivers/thermal/samsung/exynos_tmu.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/thermal/samsung/exynos_tmu.c b/drivers/thermal/samsung/exynos_tmu.c
index 3b20309789e3..c24969d740d1 100644
--- a/drivers/thermal/samsung/exynos_tmu.c
+++ b/drivers/thermal/samsung/exynos_tmu.c
@@ -666,8 +666,14 @@ static int exynos_get_temp(void *p, int *temp)
 	struct exynos_tmu_data *data = p;
 	int value, ret = 0;
 
-	if (!data || !data->tmu_read || !data->enabled)
+	if (!data || !data->tmu_read)
 		return -EINVAL;
+	else if (!data->enabled)
+		/*
+		 * Called too early, probably
+		 * from thermal_zone_of_sensor_register().
+		 */
+		return -EAGAIN;
 
 	mutex_lock(&data->lock);
 	clk_enable(data->clk);
-- 
2.14.1