[PATCH 5.4 68/71] hwmon: (dell-smm) Speed up setting of fan speed

[Greg Kroah-Hartman]

From: Armin Wolf <W_Armin@xxxxxx>

commit c0d79987a0d82671bff374c07f2201f9bdf4aaa2 upstream.

When setting the fan speed, i8k_set_fan() calls i8k_get_fan_status(),
causing an unnecessary SMM call since from the two users of this
function, only i8k_ioctl_unlocked() needs to know the new fan status
while dell_smm_write() ignores the new fan status.
Since SMM calls can be very slow while also making error reporting
difficult for dell_smm_write(), remove the function call from
i8k_set_fan() and call it separately in i8k_ioctl_unlocked().

Tested on a Dell Inspiron 3505.

Signed-off-by: Armin Wolf <W_Armin@xxxxxx>
Reviewed-by: Pali Rohár <pali@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20211021190531.17379-6-W_Armin@xxxxxx
Signed-off-by: Guenter Roeck <linux@xxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/hwmon/dell-smm-hwmon.c |   12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

--- a/drivers/hwmon/dell-smm-hwmon.c
+++ b/drivers/hwmon/dell-smm-hwmon.c
@@ -301,7 +301,7 @@ static int i8k_get_fan_nominal_speed(int
 }
 
 /*
- * Set the fan speed (off, low, high). Returns the new fan status.
+ * Set the fan speed (off, low, high, ...).
  */
 static int i8k_set_fan(int fan, int speed)
 {
@@ -313,7 +313,7 @@ static int i8k_set_fan(int fan, int spee
 	speed = (speed < 0) ? 0 : ((speed > i8k_fan_max) ? i8k_fan_max : speed);
 	regs.ebx = (fan & 0xff) | (speed << 8);
 
-	return i8k_smm(&regs) ? : i8k_get_fan_status(fan);
+	return i8k_smm(&regs);
 }
 
 static int i8k_get_temp_type(int sensor)
@@ -427,7 +427,7 @@ static int
 i8k_ioctl_unlocked(struct file *fp, unsigned int cmd, unsigned long arg)
 {
 	int val = 0;
-	int speed;
+	int speed, err;
 	unsigned char buff[16];
 	int __user *argp = (int __user *)arg;
 
@@ -488,7 +488,11 @@ i8k_ioctl_unlocked(struct file *fp, unsi
 		if (copy_from_user(&speed, argp + 1, sizeof(int)))
 			return -EFAULT;
 
-		val = i8k_set_fan(val, speed);
+		err = i8k_set_fan(val, speed);
+		if (err < 0)
+			return err;
+
+		val = i8k_get_fan_status(val);
 		break;
 
 	default: