[PATCH 1/2] hwmon: (pwm-fan) add option to leave fan on shutdown

[Akinobu Mita <akinobu.mita@gmail.com>]

This adds an optional property "retain-state-shutdown" as requested by
Billy Tsai.

Billy said:
 "Our platform is BMC that will use a PWM-FAN driver to control the fan
 on the managed host. In our case, we do not want to stop the fan when
 the BMC is reboot, which may cause the temperature of the managed host
 not to be lowered."

Cc: Rob Herring <robh+dt@kernel.org>
Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: Billy Tsai <billy_tsai@aspeedtech.com>
Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
---
 drivers/hwmon/pwm-fan.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/hwmon/pwm-fan.c b/drivers/hwmon/pwm-fan.c
index 17518b4cab1b..1ea0d0562c28 100644
--- a/drivers/hwmon/pwm-fan.c
+++ b/drivers/hwmon/pwm-fan.c
@@ -38,6 +38,7 @@ struct pwm_fan_ctx {
 	struct pwm_fan_tach *tachs;
 	ktime_t sample_start;
 	struct timer_list rpm_timer;
+	bool retain_state_shutdown;
 
 	unsigned int pwm_value;
 	unsigned int pwm_fan_state;
@@ -312,6 +313,9 @@ static int pwm_fan_probe(struct platform_device *pdev)
 
 	mutex_init(&ctx->lock);
 
+	ctx->retain_state_shutdown =
+		of_property_read_bool(dev->of_node, "retain-state-shutdown");
+
 	ctx->pwm = devm_of_pwm_get(dev, dev->of_node, NULL);
 	if (IS_ERR(ctx->pwm))
 		return dev_err_probe(dev, PTR_ERR(ctx->pwm), "Could not get PWM\n");
@@ -492,7 +496,10 @@ static int pwm_fan_disable(struct device *dev)
 
 static void pwm_fan_shutdown(struct platform_device *pdev)
 {
-	pwm_fan_disable(&pdev->dev);
+	struct pwm_fan_ctx *ctx = platform_get_drvdata(pdev);
+
+	if (!ctx->retain_state_shutdown)
+		pwm_fan_disable(&pdev->dev);
 }
 
 #ifdef CONFIG_PM_SLEEP
-- 
2.25.1