linux-kernel - [PATCH 5.15 088/171] hwmon: (pwm-fan) Ensure the fan going on in .probe()

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Date:   Mon, 13 Dec 2021 10:30:03 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Billy Tsai <billy_tsai@...eedtech.com>,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>,
        Guenter Roeck <linux@...ck-us.net>
Subject: [PATCH 5.15 088/171] hwmon: (pwm-fan) Ensure the fan going on in .probe()

From: Billy Tsai <billy_tsai@...eedtech.com>

commit a2ca752055edd39be38b887e264d3de7ca2bc1bb upstream.

Before commit 86585c61972f ("hwmon: (pwm-fan) stop using legacy
PWM functions and some cleanups") pwm_apply_state() was called
unconditionally in pwm_fan_probe(). In this commit this direct
call was replaced by a call to __set_pwm(ct, MAX_PWM) which
however is a noop if ctx->pwm_value already matches the value to
set.
After probe the fan is supposed to run at full speed, and the
internal driver state suggests it does, but this isn't asserted
and depending on bootloader and pwm low-level driver, the fan
might just be off.
So drop setting pwm_value to MAX_PWM to ensure the check in
__set_pwm doesn't make it exit early and the fan goes on as
intended.

Cc: stable@...r.kernel.org
Fixes: 86585c61972f ("hwmon: (pwm-fan) stop using legacy PWM functions and some cleanups")
Signed-off-by: Billy Tsai <billy_tsai@...eedtech.com>
Reviewed-by: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
Link: https://lore.kernel.org/r/20211130092212.17783-1-billy_tsai@aspeedtech.com
Signed-off-by: Guenter Roeck <linux@...ck-us.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/hwmon/pwm-fan.c |    2 --
 1 file changed, 2 deletions(-)

--- a/drivers/hwmon/pwm-fan.c
+++ b/drivers/hwmon/pwm-fan.c
@@ -336,8 +336,6 @@ static int pwm_fan_probe(struct platform
 			return ret;
 	}

-	ctx->pwm_value = MAX_PWM;
-
 	pwm_init_state(ctx->pwm, &ctx->pwm_state);

 	/*