hwmon/it87: Add PWM base frequency control

Let the user select the base PWM frequency when using the it87
hardware monitoring driver. Different frequencies can give better
control on some fans.

Also update the documentation to mention the PWM frequency control
files, with misc cleanups to the PWM section.
Signed-off-by: Jean Delvare <khali@linux-fr.org>

Documentation/hwmon/it87

@@ -135,6 +135,16 @@ Give 0 for unused sensor. Any other value is invalid. To configure this at
 startup, consult lm_sensors's /etc/sensors.conf. (2 = thermistor;
 3 = thermal diode)
 
+
+Fan speed control
+-----------------
+
 The fan speed control features are limited to manual PWM mode. Automatic
 "Smart Guardian" mode control handling is not implemented. However
 if you want to go for "manual mode" just write 1 to pwmN_enable.
+
+If you are only able to control the fan speed with very small PWM values,
+try lowering the PWM base frequency (pwm1_freq). Depending on the fan,
+it may give you a somewhat greater control range. The same frequency is
+used to drive all fan outputs, which is why pwm2_freq and pwm3_freq are
+read-only.

Documentation/hwmon/sysfs-interface

@@ -166,16 +166,21 @@ pwm[1-*]	Pulse width modulation fan control.
 
 pwm[1-*]_enable
 		Switch PWM on and off.
-		Not always present even if fan*_pwm is.
+		Not always present even if pwmN is.
 		0: turn off
 		1: turn on in manual mode
 		2+: turn on in automatic mode
-		Check individual chip documentation files for automatic mode details.
+		Check individual chip documentation files for automatic mode
+		details.
 		RW
 
-pwm[1-*]_mode
-		0: DC mode
-		1: PWM mode
+pwm[1-*]_mode	0: DC mode (direct current)
+		1: PWM mode (pulse-width modulation)
+		RW
+
+pwm[1-*]_freq	Base PWM frequency in Hz.
+		Only possibly available when pwmN_mode is PWM, but not always
+		present even then.
 		RW
 
 pwm[1-*]_auto_channels_temp

drivers/hwmon/it87.c

@@ -202,6 +202,17 @@ static int DIV_TO_REG(int val)
 }
 #define DIV_FROM_REG(val) (1 << (val))
 
+static const unsigned int pwm_freq[8] = {
+	48000000 / 128,
+	24000000 / 128,
+	12000000 / 128,
+	8000000 / 128,
+	6000000 / 128,
+	3000000 / 128,
+	1500000 / 128,
+	750000 / 128,
+};
+
 
 /* For each registered IT87, we need to keep some data in memory. That
    data is pointed to by it87_list[NR]->data. The structure itself is
@@ -232,6 +243,7 @@ struct it87_data {
 	u8 vrm;
 	u32 alarms;		/* Register encoding, combined */
 	u8 fan_main_ctrl;	/* Register value */
+	u8 fan_ctl;		/* Register value */
 	u8 manual_pwm_ctl[3];   /* manual PWM value set by user */
 };
 
@@ -519,6 +531,14 @@ static ssize_t show_pwm(struct device *dev, struct device_attribute *attr,
 	struct it87_data *data = it87_update_device(dev);
 	return sprintf(buf,"%d\n", data->manual_pwm_ctl[nr]);
 }
+static ssize_t show_pwm_freq(struct device *dev, struct device_attribute *attr,
+		char *buf)
+{
+	struct it87_data *data = it87_update_device(dev);
+	int index = (data->fan_ctl >> 4) & 0x07;
+
+	return sprintf(buf, "%u\n", pwm_freq[index]);
+}
 static ssize_t set_fan_min(struct device *dev, struct device_attribute *attr,
 		const char *buf, size_t count)
 {
@@ -639,6 +659,28 @@ static ssize_t set_pwm(struct device *dev, struct device_attribute *attr,
 	mutex_unlock(&data->update_lock);
 	return count;
 }
+static ssize_t set_pwm_freq(struct device *dev,
+		struct device_attribute *attr, const char *buf, size_t count)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct it87_data *data = i2c_get_clientdata(client);
+	unsigned long val = simple_strtoul(buf, NULL, 10);
+	int i;
+
+	/* Search for the nearest available frequency */
+	for (i = 0; i < 7; i++) {
+		if (val > (pwm_freq[i] + pwm_freq[i+1]) / 2)
+			break;
+	}
+
+	mutex_lock(&data->update_lock);
+	data->fan_ctl = it87_read_value(client, IT87_REG_FAN_CTL) & 0x8f;
+	data->fan_ctl |= i << 4;
+	it87_write_value(client, IT87_REG_FAN_CTL, data->fan_ctl);
+	mutex_unlock(&data->update_lock);
+
+	return count;
+}
 
 #define show_fan_offset(offset)					\
 static SENSOR_DEVICE_ATTR(fan##offset##_input, S_IRUGO,		\
@@ -656,7 +698,10 @@ show_fan_offset(3);
 static SENSOR_DEVICE_ATTR(pwm##offset##_enable, S_IRUGO | S_IWUSR,	\
 		show_pwm_enable, set_pwm_enable, offset - 1);		\
 static SENSOR_DEVICE_ATTR(pwm##offset, S_IRUGO | S_IWUSR,		\
-		show_pwm, set_pwm, offset - 1);
+		show_pwm, set_pwm, offset - 1);				\
+static DEVICE_ATTR(pwm##offset##_freq,					\
+		(offset == 1 ? S_IRUGO | S_IWUSR : S_IRUGO),		\
+		show_pwm_freq, (offset == 1 ? set_pwm_freq : NULL));
 
 show_pwm_offset(1);
 show_pwm_offset(2);
@@ -1021,7 +1066,13 @@ static int it87_detect(struct i2c_adapter *adapter)
 		 || (err = device_create_file(&new_client->dev,
 		     &sensor_dev_attr_pwm2.dev_attr))
 		 || (err = device_create_file(&new_client->dev,
-		     &sensor_dev_attr_pwm3.dev_attr)))
+		     &sensor_dev_attr_pwm3.dev_attr))
+		 || (err = device_create_file(&new_client->dev,
+		     &dev_attr_pwm1_freq))
+		 || (err = device_create_file(&new_client->dev,
+		     &dev_attr_pwm2_freq))
+		 || (err = device_create_file(&new_client->dev,
+		     &dev_attr_pwm3_freq)))
 			goto ERROR4;
 	}
 
@@ -1316,6 +1367,7 @@ static struct it87_data *it87_update_device(struct device *dev)
 			(it87_read_value(client, IT87_REG_ALARM2) << 8) |
 			(it87_read_value(client, IT87_REG_ALARM3) << 16);
 		data->fan_main_ctrl = it87_read_value(client, IT87_REG_FAN_MAIN_CTRL);
+		data->fan_ctl = it87_read_value(client, IT87_REG_FAN_CTL);
 
 		data->sensor = it87_read_value(client, IT87_REG_TEMP_ENABLE);
 		/* The 8705 does not have VID capability */