[PATCH 4.14 43/44] hwmon: (dell-smm) Speed up setting of fan speed

Greg Kroah-Hartman
2022-02-14T09:33:43Z

From: Armin Wolf <W_Armin@gmx.de>

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@gmx.de>
Reviewed-by: Pali Rohár <pali@kernel.org>
Link: https://lore.kernel.org/r/20211021190531.17379-6-W_Armin@gmx.de
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
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
@@ -294,7 +294,7 @@ 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)
{
@@ -303,7 +303,7 @@ 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)
@@ -417,7 +417,7 @@ 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;

@@ -478,7 +478,11 @@ 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;