On 22/05/2016 13:50, Pali Rohár wrote: > This patch exports standard hwmon pwmX_enable sysfs attribute for enabling > or disabling automatic fan control by BIOS. Standard value "1" is for > disabling automatic BIOS fan control and value "2" for enabling. > > Currently there is no way to check if BIOS auto mode is enabled (at least > it is not know how to do it), so hwmon sysfs attribute is write-only. > > By default BIOS auto mode is enabled by laptop firmware. > > When BIOS auto mode is enabled, custom fan speed value (set via hwmon pwmX > sysfs attribute) is overwritten by SMM in few seconds and therefore any > custom settings are without effect. So this is reason why implementing > option for disabling BIOS auto mode is needed. > > So finally this patch allows kernel to set and control fan speed on > laptops, but it can be dangerous (like setting speed of other fans). > > This new feature is highly experimental, uses Dell SMM calls, so does not > have to be supported by all laptops BIOSes. It was tested on Dell Latitude > E6440 with BIOS A5.
Tested on a Dell XPS13 9333. Changing the value of pwm1_enable appears to have no effect here. > Signed-off-by: Pali Rohár <pali.ro...@gmail.com> > --- > drivers/hwmon/dell-smm-hwmon.c | 64 > ++++++++++++++++++++++++++++++++++------ > 1 file changed, 55 insertions(+), 9 deletions(-) > > diff --git a/drivers/hwmon/dell-smm-hwmon.c b/drivers/hwmon/dell-smm-hwmon.c > index 8a66a42..7b5144a 100644 > --- a/drivers/hwmon/dell-smm-hwmon.c > +++ b/drivers/hwmon/dell-smm-hwmon.c > @@ -45,6 +45,8 @@ > #define I8K_SMM_GET_SPEED 0x02a3 > #define I8K_SMM_GET_FAN_TYPE 0x03a3 > #define I8K_SMM_GET_NOM_SPEED 0x04a3 > +#define I8K_SMM_MANUAL_FAN 0x34a3 > +#define I8K_SMM_AUTO_FAN 0x35a3 > #define I8K_SMM_GET_TEMP 0x10a3 > #define I8K_SMM_GET_TEMP_TYPE 0x11a3 > #define I8K_SMM_GET_DELL_SIG1 0xfea3 > @@ -284,6 +286,17 @@ static int i8k_get_fan_nominal_speed(int fan, int speed) > } > > /* > + * Enable or disable automatic BIOS fan control support > + */ > +static int i8k_enable_fan_auto_mode(bool enable) > +{ > + struct smm_regs regs = { }; > + > + regs.eax = enable ? I8K_SMM_AUTO_FAN : I8K_SMM_MANUAL_FAN; > + return i8k_smm(®s); > +} > + > +/* > * Set the fan speed (off, low, high). Returns the new fan status. > */ > static int i8k_set_fan(int fan, int speed) > @@ -702,6 +715,30 @@ static ssize_t i8k_hwmon_set_pwm(struct device *dev, > return err < 0 ? -EIO : count; > } > > +static ssize_t i8k_hwmon_set_pwm_enable(struct device *dev, > + struct device_attribute *attr, > + const char *buf, size_t count) > +{ > + int err; > + bool enable; > + unsigned long val; > + > + err = kstrtoul(buf, 10, &val); > + if (err) > + return err; > + > + if (val == 0) > + return -EINVAL; > + > + enable = (val != 1); > + > + mutex_lock(&i8k_mutex); > + err = i8k_enable_fan_auto_mode(enable); > + mutex_unlock(&i8k_mutex); > + > + return err ? -EIO : count; > +} > + > static SENSOR_DEVICE_ATTR(temp1_input, S_IRUGO, i8k_hwmon_show_temp, NULL, > 0); > static SENSOR_DEVICE_ATTR(temp1_label, S_IRUGO, i8k_hwmon_show_temp_label, > NULL, > 0); > @@ -719,18 +756,24 @@ static SENSOR_DEVICE_ATTR(fan1_label, S_IRUGO, > i8k_hwmon_show_fan_label, NULL, > 0); > static SENSOR_DEVICE_ATTR(pwm1, S_IRUGO | S_IWUSR, i8k_hwmon_show_pwm, > i8k_hwmon_set_pwm, 0); > +static SENSOR_DEVICE_ATTR(pwm1_enable, S_IWUSR, NULL, > i8k_hwmon_set_pwm_enable, > + 0); > static SENSOR_DEVICE_ATTR(fan2_input, S_IRUGO, i8k_hwmon_show_fan, NULL, > 1); > static SENSOR_DEVICE_ATTR(fan2_label, S_IRUGO, i8k_hwmon_show_fan_label, > NULL, > 1); > static SENSOR_DEVICE_ATTR(pwm2, S_IRUGO | S_IWUSR, i8k_hwmon_show_pwm, > i8k_hwmon_set_pwm, 1); > +static SENSOR_DEVICE_ATTR(pwm2_enable, S_IWUSR, NULL, > i8k_hwmon_set_pwm_enable, > + 1); > static SENSOR_DEVICE_ATTR(fan3_input, S_IRUGO, i8k_hwmon_show_fan, NULL, > 2); > static SENSOR_DEVICE_ATTR(fan3_label, S_IRUGO, i8k_hwmon_show_fan_label, > NULL, > 2); > static SENSOR_DEVICE_ATTR(pwm3, S_IRUGO | S_IWUSR, i8k_hwmon_show_pwm, > i8k_hwmon_set_pwm, 2); > +static SENSOR_DEVICE_ATTR(pwm3_enable, S_IWUSR, NULL, > i8k_hwmon_set_pwm_enable, > + 2); > > static struct attribute *i8k_attrs[] = { > &sensor_dev_attr_temp1_input.dev_attr.attr, /* 0 */ > @@ -744,12 +787,15 @@ static struct attribute *i8k_attrs[] = { > &sensor_dev_attr_fan1_input.dev_attr.attr, /* 8 */ > &sensor_dev_attr_fan1_label.dev_attr.attr, /* 9 */ > &sensor_dev_attr_pwm1.dev_attr.attr, /* 10 */ > - &sensor_dev_attr_fan2_input.dev_attr.attr, /* 11 */ > - &sensor_dev_attr_fan2_label.dev_attr.attr, /* 12 */ > - &sensor_dev_attr_pwm2.dev_attr.attr, /* 13 */ > - &sensor_dev_attr_fan3_input.dev_attr.attr, /* 14 */ > - &sensor_dev_attr_fan3_label.dev_attr.attr, /* 15 */ > - &sensor_dev_attr_pwm3.dev_attr.attr, /* 16 */ > + &sensor_dev_attr_pwm1_enable.dev_attr.attr, /* 11 */ > + &sensor_dev_attr_fan2_input.dev_attr.attr, /* 12 */ > + &sensor_dev_attr_fan2_label.dev_attr.attr, /* 13 */ > + &sensor_dev_attr_pwm2.dev_attr.attr, /* 14 */ > + &sensor_dev_attr_pwm2_enable.dev_attr.attr, /* 15 */ > + &sensor_dev_attr_fan3_input.dev_attr.attr, /* 16 */ > + &sensor_dev_attr_fan3_label.dev_attr.attr, /* 17 */ > + &sensor_dev_attr_pwm3.dev_attr.attr, /* 18 */ > + &sensor_dev_attr_pwm3_enable.dev_attr.attr, /* 19 */ > NULL > }; > > @@ -768,13 +814,13 @@ static umode_t i8k_is_visible(struct kobject *kobj, > struct attribute *attr, > if (index >= 6 && index <= 7 && > !(i8k_hwmon_flags & I8K_HWMON_HAVE_TEMP4)) > return 0; > - if (index >= 8 && index <= 10 && > + if (index >= 8 && index <= 11 && > !(i8k_hwmon_flags & I8K_HWMON_HAVE_FAN1)) > return 0; > - if (index >= 11 && index <= 13 && > + if (index >= 12 && index <= 15 && > !(i8k_hwmon_flags & I8K_HWMON_HAVE_FAN2)) > return 0; > - if (index >= 14 && index <= 16 && > + if (index >= 16 && index <= 19 && > !(i8k_hwmon_flags & I8K_HWMON_HAVE_FAN3)) > return 0; > >