The driver caches the PWM frequency register and the CONFIG_FAN slow-clock
select bit, but never lets userspace pick a different output frequency.
Add a pwm1_freq sysfs attribute that selects the closest SCS + PFR
combination for the requested value in Hz, gated by manual mode like
set_pwm1(). PFR is clamped to 31 so that 2*PFR fits in the chip's 6-bit
PWM register (matching the existing scaling assumption in show_pwm1).

The hardware LUT hysteresis register is shared by all LUT entries, so
the per-point pwm1_auto_pointN_temp_hyst attributes can't be made RW
without N-to-1 cross-attribute side effects. Following the max31760
precedent, expose a single chip-wide pwm1_auto_point_temp_hyst attribute
holding the hysteresis amount in millidegrees; the per-point attributes
stay RO and continue to show the resulting absolute trip-down
temperature for each entry.

This was tested on a Linksys LGS328MPC switch hardware where the fan
would not spin with the default PWM Frequency, which is why this change
is required.

Signed-off-by: Jan-Henrik Bruhn <kernel@jhbruhn.de>
---
 drivers/hwmon/lm63.c | 112 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 112 insertions(+)

diff --git a/drivers/hwmon/lm63.c b/drivers/hwmon/lm63.c
index a0d77a7386a9..0fc4a2f0c308 100644
--- a/drivers/hwmon/lm63.c
+++ b/drivers/hwmon/lm63.c
@@ -92,6 +92,9 @@ static const unsigned short normal_i2c[] = { 0x18, 0x4c, 0x4e, I2C_CLIENT_END };
 #define LM96163_REG_REMOTE_TEMP_U_LSB	0x32
 #define LM96163_REG_CONFIG_ENHANCED	0x45
 
+#define LM63_PWM_BASE_FAST_HZ		180000
+#define LM63_PWM_BASE_SLOW_HZ		700
+
 #define LM63_MAX_CONVRATE		9
 
 #define LM63_MAX_CONVRATE_HZ		32
@@ -455,6 +458,75 @@ static ssize_t pwm1_enable_store(struct device *dev,
 	return count;
 }
 
+static ssize_t pwm1_freq_show(struct device *dev,
+			      struct device_attribute *dummy, char *buf)
+{
+	struct lm63_data *data = lm63_update_device(dev);
+	unsigned int base = (data->config_fan & 0x08) ?
+			    LM63_PWM_BASE_SLOW_HZ : LM63_PWM_BASE_FAST_HZ;
+
+	return sprintf(buf, "%u\n", base / data->pwm1_freq);
+}
+
+/*
+ * Pick the closest CONFIG_FAN.SCS + PFR for the requested frequency.
+ * PWM_FREQ writes need the LUT unlocked, same as set_pwm1(). LUT PWM
+ * bytes are register-relative; rewrite them after a frequency change
+ * if duty cycles must be preserved.
+ */
+static ssize_t pwm1_freq_store(struct device *dev,
+			       struct device_attribute *dummy,
+			       const char *buf, size_t count)
+{
+	struct lm63_data *data = dev_get_drvdata(dev);
+	struct i2c_client *client = data->client;
+	unsigned long val, pfr_fast, pfr_slow, err_fast, err_slow, pfr;
+	bool slow_clock;
+	int err;
+
+	if (!(data->config_fan & 0x20)) /* register is read-only */
+		return -EPERM;
+
+	err = kstrtoul(buf, 10, &val);
+	if (err)
+		return err;
+	if (val == 0)
+		return -EINVAL;
+
+	pfr_fast = clamp_val(DIV_ROUND_CLOSEST((unsigned long)LM63_PWM_BASE_FAST_HZ, val),
+			     1UL, 31UL);
+	pfr_slow = clamp_val(DIV_ROUND_CLOSEST((unsigned long)LM63_PWM_BASE_SLOW_HZ, val),
+			     1UL, 31UL);
+	err_fast = abs_diff(LM63_PWM_BASE_FAST_HZ / pfr_fast, val);
+	err_slow = abs_diff(LM63_PWM_BASE_SLOW_HZ / pfr_slow, val);
+
+	if (err_slow < err_fast) {
+		slow_clock = true;
+		pfr = pfr_slow;
+	} else {
+		slow_clock = false;
+		pfr = pfr_fast;
+	}
+
+	mutex_lock(&data->update_lock);
+	data->config_fan = i2c_smbus_read_byte_data(client, LM63_REG_CONFIG_FAN);
+	if (slow_clock)
+		data->config_fan |= 0x08;
+	else
+		data->config_fan &= ~0x08;
+	i2c_smbus_write_byte_data(client, LM63_REG_CONFIG_FAN, data->config_fan);
+	i2c_smbus_write_byte_data(client, LM63_REG_PWM_FREQ, pfr);
+	data->pwm1_freq = pfr;
+
+	if (data->kind == lm96163) {
+		u8 enh = i2c_smbus_read_byte_data(client,
+						  LM96163_REG_CONFIG_ENHANCED);
+		data->pwm_highres = !slow_clock && pfr == 8 && (enh & 0x10);
+	}
+	mutex_unlock(&data->update_lock);
+	return count;
+}
+
 /*
  * There are 8bit registers for both local(temp1) and remote(temp2) sensor.
  * For remote sensor registers temp2_offset has to be considered,
@@ -629,6 +701,42 @@ static ssize_t show_lut_temp_hyst(struct device *dev,
 	return sprintf(buf, "%d\n", temp);
 }
 
+/*
+ * The LM63 has a single hysteresis register shared by all LUT entries.
+ * Expose it as a chip-wide hysteresis amount in millidegrees; the
+ * per-point pwm1_auto_pointN_temp_hyst attributes remain read-only and
+ * show the resulting absolute trip-down temperature for each entry.
+ */
+static ssize_t pwm1_auto_point_temp_hyst_show(struct device *dev,
+					      struct device_attribute *dummy,
+					      char *buf)
+{
+	struct lm63_data *data = lm63_update_device(dev);
+
+	return sprintf(buf, "%d\n", TEMP8_FROM_REG(data->lut_temp_hyst));
+}
+
+static ssize_t pwm1_auto_point_temp_hyst_store(struct device *dev,
+					       struct device_attribute *dummy,
+					       const char *buf, size_t count)
+{
+	struct lm63_data *data = dev_get_drvdata(dev);
+	struct i2c_client *client = data->client;
+	unsigned long val;
+	int err;
+
+	err = kstrtoul(buf, 10, &val);
+	if (err)
+		return err;
+
+	mutex_lock(&data->update_lock);
+	data->lut_temp_hyst = HYST_TO_REG(val);
+	i2c_smbus_write_byte_data(client, LM63_REG_LUT_TEMP_HYST,
+				  data->lut_temp_hyst);
+	mutex_unlock(&data->update_lock);
+	return count;
+}
+
 /*
  * And now the other way around, user-space provides an absolute
  * hysteresis value and we have to store a relative one
@@ -764,6 +872,8 @@ static SENSOR_DEVICE_ATTR(fan1_min, S_IWUSR | S_IRUGO, show_fan,
 
 static SENSOR_DEVICE_ATTR(pwm1, S_IWUSR | S_IRUGO, show_pwm1, set_pwm1, 0);
 static DEVICE_ATTR_RW(pwm1_enable);
+static DEVICE_ATTR_RW(pwm1_freq);
+static DEVICE_ATTR_RW(pwm1_auto_point_temp_hyst);
 static SENSOR_DEVICE_ATTR(pwm1_auto_point1_pwm, S_IWUSR | S_IRUGO,
 	show_pwm1, set_pwm1, 1);
 static SENSOR_DEVICE_ATTR(pwm1_auto_point1_temp, S_IWUSR | S_IRUGO,
@@ -869,6 +979,8 @@ static DEVICE_ATTR_RW(update_interval);
 static struct attribute *lm63_attributes[] = {
 	&sensor_dev_attr_pwm1.dev_attr.attr,
 	&dev_attr_pwm1_enable.attr,
+	&dev_attr_pwm1_freq.attr,
+	&dev_attr_pwm1_auto_point_temp_hyst.attr,
 	&sensor_dev_attr_pwm1_auto_point1_pwm.dev_attr.attr,
 	&sensor_dev_attr_pwm1_auto_point1_temp.dev_attr.attr,
 	&sensor_dev_attr_pwm1_auto_point1_temp_hyst.dev_attr.attr,
-- 
2.48.1