hwmon: (adt7470) Expose PWM frequency to sysfs

The ADT7470 supports a variety of PWM frequencies. This patch allows the
frequency to be configured and viewed through the sysfs entry pwm1_freq.

Signed-off-by: Joshua Scott <joshua.scott@alliedtelesis.co.nz>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

Documentation/hwmon/adt7470

@@ -65,6 +65,23 @@ from 0 (off) to 255 (full speed).  Fan speed will be set to maximum when the
 temperature sensor associated with the PWM control exceeds
 pwm#_auto_point2_temp.
 
+The driver also allows control of the PWM frequency:
+
+* pwm1_freq
+
+The PWM frequency is rounded to the nearest one of:
+
+* 11.0 Hz
+* 14.7 Hz
+* 22.1 Hz
+* 29.4 Hz
+* 35.3 Hz
+* 44.1 Hz
+* 58.8 Hz
+* 88.2 Hz
+* 1.4 kHz
+* 22.5 kHz
+
 Notes
 -----
 

drivers/hwmon/adt7470.c

@@ -32,6 +32,7 @@
 #include <linux/log2.h>
 #include <linux/kthread.h>
 #include <linux/slab.h>
+#include <linux/util_macros.h>
 
 /* Addresses to scan */
 static const unsigned short normal_i2c[] = { 0x2C, 0x2E, 0x2F, I2C_CLIENT_END };
@@ -83,6 +84,7 @@ static const unsigned short normal_i2c[] = { 0x2C, 0x2E, 0x2F, I2C_CLIENT_END };
 #define ADT7470_REG_PWM_MIN_MAX_ADDR		0x6D
 #define ADT7470_REG_PWM_TEMP_MIN_BASE_ADDR	0x6E
 #define ADT7470_REG_PWM_TEMP_MIN_MAX_ADDR	0x71
+#define ADT7470_REG_CFG_2			0x74
 #define ADT7470_REG_ACOUSTICS12			0x75
 #define ADT7470_REG_ACOUSTICS34			0x76
 #define ADT7470_REG_DEVICE			0x3D
@@ -142,6 +144,11 @@ static const unsigned short normal_i2c[] = { 0x2C, 0x2E, 0x2F, I2C_CLIENT_END };
 #define FAN_PERIOD_INVALID	65535
 #define FAN_DATA_VALID(x)	((x) && (x) != FAN_PERIOD_INVALID)
 
+/* Config registers 1 and 2 include fields for selecting the PWM frequency */
+#define ADT7470_CFG_LF		0x40
+#define ADT7470_FREQ_MASK	0x70
+#define ADT7470_FREQ_SHIFT	4
+
 struct adt7470_data {
 	struct i2c_client	*client;
 	struct mutex		lock;
@@ -688,6 +695,70 @@ static ssize_t set_pwm(struct device *dev, struct device_attribute *devattr,
 	return count;
 }
 
+/* These are the valid PWM frequencies to the nearest Hz */
+static const int adt7470_freq_map[] = {
+	11, 15, 22, 29, 35, 44, 59, 88, 1400, 22500
+};
+
+static ssize_t show_pwm_freq(struct device *dev,
+			     struct device_attribute *devattr, char *buf)
+{
+	struct adt7470_data *data = adt7470_update_device(dev);
+	unsigned char cfg_reg_1;
+	unsigned char cfg_reg_2;
+	int index;
+
+	mutex_lock(&data->lock);
+	cfg_reg_1 = i2c_smbus_read_byte_data(data->client, ADT7470_REG_CFG);
+	cfg_reg_2 = i2c_smbus_read_byte_data(data->client, ADT7470_REG_CFG_2);
+	mutex_unlock(&data->lock);
+
+	index = (cfg_reg_2 & ADT7470_FREQ_MASK) >> ADT7470_FREQ_SHIFT;
+	if (!(cfg_reg_1 & ADT7470_CFG_LF))
+		index += 8;
+	if (index >= ARRAY_SIZE(adt7470_freq_map))
+		index = ARRAY_SIZE(adt7470_freq_map) - 1;
+
+	return scnprintf(buf, PAGE_SIZE, "%d\n", adt7470_freq_map[index]);
+}
+
+static ssize_t set_pwm_freq(struct device *dev,
+			    struct device_attribute *devattr,
+			    const char *buf, size_t count)
+{
+	struct adt7470_data *data = dev_get_drvdata(dev);
+	struct i2c_client *client = data->client;
+	long freq;
+	int index;
+	int low_freq = ADT7470_CFG_LF;
+	unsigned char val;
+
+	if (kstrtol(buf, 10, &freq))
+		return -EINVAL;
+
+	/* Round the user value given to the closest available frequency */
+	index = find_closest(freq, adt7470_freq_map,
+			     ARRAY_SIZE(adt7470_freq_map));
+
+	if (index >= 8) {
+		index -= 8;
+		low_freq = 0;
+	}
+
+	mutex_lock(&data->lock);
+	/* Configuration Register 1 */
+	val = i2c_smbus_read_byte_data(client, ADT7470_REG_CFG);
+	i2c_smbus_write_byte_data(client, ADT7470_REG_CFG,
+				  (val & ~ADT7470_CFG_LF) | low_freq);
+	/* Configuration Register 2 */
+	val = i2c_smbus_read_byte_data(client, ADT7470_REG_CFG_2);
+	i2c_smbus_write_byte_data(client, ADT7470_REG_CFG_2,
+		(val & ~ADT7470_FREQ_MASK) | (index << ADT7470_FREQ_SHIFT));
+	mutex_unlock(&data->lock);
+
+	return count;
+}
+
 static ssize_t show_pwm_max(struct device *dev,
 			    struct device_attribute *devattr,
 			    char *buf)
@@ -1038,6 +1109,8 @@ static SENSOR_DEVICE_ATTR(pwm2, S_IWUSR | S_IRUGO, show_pwm, set_pwm, 1);
 static SENSOR_DEVICE_ATTR(pwm3, S_IWUSR | S_IRUGO, show_pwm, set_pwm, 2);
 static SENSOR_DEVICE_ATTR(pwm4, S_IWUSR | S_IRUGO, show_pwm, set_pwm, 3);
 
+static DEVICE_ATTR(pwm1_freq, S_IWUSR | S_IRUGO, show_pwm_freq, set_pwm_freq);
+
 static SENSOR_DEVICE_ATTR(pwm1_auto_point1_pwm, S_IWUSR | S_IRUGO,
 		    show_pwm_min, set_pwm_min, 0);
 static SENSOR_DEVICE_ATTR(pwm2_auto_point1_pwm, S_IWUSR | S_IRUGO,
@@ -1154,6 +1227,7 @@ static struct attribute *adt7470_attrs[] = {
 	&sensor_dev_attr_fan4_alarm.dev_attr.attr,
 	&sensor_dev_attr_force_pwm_max.dev_attr.attr,
 	&sensor_dev_attr_pwm1.dev_attr.attr,
+	&dev_attr_pwm1_freq.attr,
 	&sensor_dev_attr_pwm2.dev_attr.attr,
 	&sensor_dev_attr_pwm3.dev_attr.attr,
 	&sensor_dev_attr_pwm4.dev_attr.attr,