linux-kernel - [PATCH 4.4 258/342] hwmon: (gpio-fan) Remove un-necessary speed

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Date:	Tue, 01 Mar 2016 23:55:10 +0000
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	<linux-kernel@...r.kernel.org>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	<stable@...r.kernel.org>, Tony Lindgren <tony@...mide.com>,
	Guenter Roeck <linux@...ck-us.net>,
	Eduardo Valentin <edubezval@...il.com>,
	Nishanth Menon <nm@...com>
Subject: [PATCH 4.4 258/342] hwmon: (gpio-fan) Remove un-necessary speed_index lookup for thermal hook

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Nishanth Menon <nm@...com>

commit 000e0949148382c4962489593a2f05504c2a6771 upstream.

Thermal hook gpio_fan_get_cur_state is only interested in knowing
the current speed index that was setup in the system, this is
already available as part of fan_data->speed_index which is always
set by set_fan_speed. Using get_fan_speed_index is useful when we
have no idea about the fan speed configuration (for example during
fan_ctrl_init).

When thermal framework invokes
gpio_fan_get_cur_state=>get_fan_speed_index via gpio_fan_get_cur_state
especially in a polled configuration for thermal governor, we
basically hog the i2c interface to the extent that other functions
fail to get any traffic out :(.

Instead, just provide the last state set in the driver - since the gpio
fan driver is responsible for the fan state immaterial of override, the
fan_data->speed_index should accurately reflect the state.

Fixes: b5cf88e46bad ("(gpio-fan): Add thermal control hooks")
Reported-by: Tony Lindgren <tony@...mide.com>
Cc: Guenter Roeck <linux@...ck-us.net>
Cc: Eduardo Valentin <edubezval@...il.com>
Signed-off-by: Nishanth Menon <nm@...com>
Signed-off-by: Guenter Roeck <linux@...ck-us.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/hwmon/gpio-fan.c |    7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

--- a/drivers/hwmon/gpio-fan.c
+++ b/drivers/hwmon/gpio-fan.c
@@ -406,16 +406,11 @@ static int gpio_fan_get_cur_state(struct
 				  unsigned long *state)
 {
 	struct gpio_fan_data *fan_data = cdev->devdata;
-	int r;

 	if (!fan_data)
 		return -EINVAL;

-	r = get_fan_speed_index(fan_data);
-	if (r < 0)
-		return r;
-
-	*state = r;
+	*state = fan_data->speed_index;
 	return 0;
 }