Re: [PATCH] hwmon: (adt7470) Add support for PWM inversion

Guenter Roeck <linux@xxxxxxxxxxxx> · Wed, 18 Aug 2021 10:53:17 -0700

On 8/18/21 9:34 AM, Robert Hancock wrote:
On Tue, 2021-08-17 at 20:26 -0700, Guenter Roeck wrote:
On 8/16/21 1:35 PM, Robert Hancock wrote:
Add sysfs attributes to control whether the PWM output signal from the
device is inverted (i.e. active-low rather than active-high).


We would normally call that "polarity".

Anyway, what is the use case ? The pwm polarity is not a fan property but
a system property. While many of the hwmon sysfs attributes describe system
properties, that is for the most part a leftover from times when PCs
did not provide the necessary information, and it was necessary to
configure hwmon devices from userspace.

Nowadays, system properties are typically provided with devicetree
properties or with the ACPI equivalent. A good example is the driver
for adt7575. Would that solve your problem ?

In our case the board we are using with this device has a transistor between
the ADT7470 PWM output and the fan PWM input, which results in the signal being
inverted. So this is effectively a hardware property, which could belong in the
device tree. The PWM frequency is another property we are setting that could
belong there as well.

Right now the ADT7470 driver doesn't do anything with the device tree at all,
the entry in the DT for the device is only useful for probing. I suppose it
could get some code to initialize the default settings for some of these values
from the device tree if they are present and still provide the sysfs interface
for backward compatibility?

Sure, but only for the existing attributes.

You mentioned adt7575, I assume you meant adt7475 - it has an adi,pwm-active-

Yes, sorry. Fat finger.

state value that can be defined to set the PWM as active low or active high for
each output. We could do something similar here. Not sure if anything else is
setting PWM frequencies in the device tree right now? I see some in-tree DTSes
which set a maxim,fan-pwm-freq property but I don't see any driver in tree that
reads that property.

The definition was submitted recently but Rob didn't like it because the
properties are listed as Maxim-specific but should be generic. At some point
someone will have to spend the time and propose a set of standard properties.

Anyway, the pwm subsystem uses 'clocks' properties for this purpose.
The npcm750-pwm-fan driver uses the same mechanism. Maybe we should use that
here.

Thanks,
Guenter


Thanks,
Guenter

Signed-off-by: Robert Hancock <robert.hancock@xxxxxxxxxx>
---
   Documentation/hwmon/adt7470.rst |  5 ++-
   drivers/hwmon/adt7470.c         | 72 ++++++++++++++++++++++++++++++++-
   2 files changed, 75 insertions(+), 2 deletions(-)

diff --git a/Documentation/hwmon/adt7470.rst
b/Documentation/hwmon/adt7470.rst
index d225f816e992..8293f93d6cd5 100644
--- a/Documentation/hwmon/adt7470.rst
+++ b/Documentation/hwmon/adt7470.rst
@@ -69,7 +69,10 @@ 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:
+The driver also allows control of the PWM inversion and frequency:
+
+* pwm#_invert: Controls whether the PWM output signal is inverted
+  (i.e. low when active rather than high).
   
   * pwm1_freq
   
diff --git a/drivers/hwmon/adt7470.c b/drivers/hwmon/adt7470.c
index 2e8feacccf84..f0863a6e1560 100644
--- a/drivers/hwmon/adt7470.c
+++ b/drivers/hwmon/adt7470.c
@@ -61,10 +61,14 @@ static const unsigned short normal_i2c[] = { 0x2C,
0x2E, 0x2F, I2C_CLIENT_END };
   #define ADT7470_REG_FAN_MAX_MAX_ADDR		0x67
   #define ADT7470_REG_PWM_CFG_BASE_ADDR		0x68
   #define ADT7470_REG_PWM12_CFG			0x68
+#define		ADT7470_PWM2_INVERT_MASK	0x10
+#define		ADT7470_PWM1_INVERT_MASK	0x20
   #define		ADT7470_PWM2_AUTO_MASK		0x40
   #define		ADT7470_PWM1_AUTO_MASK		0x80
   #define		ADT7470_PWM_AUTO_MASK		0xC0
   #define ADT7470_REG_PWM34_CFG			0x69
+#define		ADT7470_PWM4_INVERT_MASK	0x10
+#define		ADT7470_PWM3_INVERT_MASK	0x20
   #define		ADT7470_PWM3_AUTO_MASK		0x40
   #define		ADT7470_PWM4_AUTO_MASK		0x80
   #define	ADT7470_REG_PWM_MIN_BASE_ADDR		0x6A
@@ -162,6 +166,7 @@ struct adt7470_data {
   	u8			pwm_min[ADT7470_PWM_COUNT];
   	s8			pwm_tmin[ADT7470_PWM_COUNT];
   	u8			pwm_auto_temp[ADT7470_PWM_COUNT];
+	u8			pwm_invert[ADT7470_PWM_COUNT];
   
   	struct task_struct	*auto_update;
   	unsigned int		auto_update_interval;
@@ -300,11 +305,22 @@ static int adt7470_update_sensors(struct adt7470_data
*data)
   			reg_mask = ADT7470_PWM1_AUTO_MASK;
   
   		reg = ADT7470_REG_PWM_CFG(i);
-		if (i2c_smbus_read_byte_data(client, reg) & reg_mask)
+		cfg = i2c_smbus_read_byte_data(client, reg);
+		if (cfg & reg_mask)
   			data->pwm_automatic[i] = 1;
   		else
   			data->pwm_automatic[i] = 0;
   
+		if (i % 2)
+			reg_mask = ADT7470_PWM2_INVERT_MASK;
+		else
+			reg_mask = ADT7470_PWM1_INVERT_MASK;
+
+		if (cfg & reg_mask)
+			data->pwm_invert[i] = 1;
+		else
+			data->pwm_invert[i] = 0;
+
   		reg = ADT7470_REG_PWM_AUTO_TEMP(i);
   		cfg = i2c_smbus_read_byte_data(client, reg);
   		if (!(i % 2))
@@ -935,6 +951,51 @@ static ssize_t pwm_tmin_store(struct device *dev,
   	return count;
   }
   
+static ssize_t pwm_invert_show(struct device *dev,
+			       struct device_attribute *devattr, char *buf)
+{
+	struct sensor_device_attribute *attr = to_sensor_dev_attr(devattr);
+	struct adt7470_data *data = adt7470_update_device(dev);
+
+	return sprintf(buf, "%d\n", (int)data->pwm_invert[attr->index]);
+}
+
+static ssize_t pwm_invert_store(struct device *dev,
+				struct device_attribute *devattr,
+				const char *buf, size_t count)
+{
+	struct sensor_device_attribute *attr = to_sensor_dev_attr(devattr);
+	struct adt7470_data *data = dev_get_drvdata(dev);
+	struct i2c_client *client = data->client;
+	int pwm_invert_reg = ADT7470_REG_PWM_CFG(attr->index);
+	int pwm_invert_reg_mask;
+	long temp;
+	u8 reg;
+
+	if (kstrtol(buf, 10, &temp))
+		return -EINVAL;
+
+	if (attr->index % 2)
+		pwm_invert_reg_mask = ADT7470_PWM2_INVERT_MASK;
+	else
+		pwm_invert_reg_mask = ADT7470_PWM1_INVERT_MASK;
+
+	if (temp != 1 && temp != 0)
+		return -EINVAL;
+
+	mutex_lock(&data->lock);
+	data->pwm_invert[attr->index] = temp;
+	reg = i2c_smbus_read_byte_data(client, pwm_invert_reg);
+	if (temp)
+		reg |= pwm_invert_reg_mask;
+	else
+		reg &= ~pwm_invert_reg_mask;
+	i2c_smbus_write_byte_data(client, pwm_invert_reg, reg);
+	mutex_unlock(&data->lock);
+
+	return count;
+}
+
   static ssize_t pwm_auto_show(struct device *dev,
   			     struct device_attribute *devattr, char *buf)
   {
@@ -1135,6 +1196,11 @@ static SENSOR_DEVICE_ATTR_RW(pwm4, pwm, 3);
   
   static DEVICE_ATTR_RW(pwm1_freq);
   
+static SENSOR_DEVICE_ATTR_RW(pwm1_invert, pwm_invert, 0);
+static SENSOR_DEVICE_ATTR_RW(pwm2_invert, pwm_invert, 1);
+static SENSOR_DEVICE_ATTR_RW(pwm3_invert, pwm_invert, 2);
+static SENSOR_DEVICE_ATTR_RW(pwm4_invert, pwm_invert, 3);
+
   static SENSOR_DEVICE_ATTR_RW(pwm1_auto_point1_pwm, pwm_min, 0);
   static SENSOR_DEVICE_ATTR_RW(pwm2_auto_point1_pwm, pwm_min, 1);
   static SENSOR_DEVICE_ATTR_RW(pwm3_auto_point1_pwm, pwm_min, 2);
@@ -1231,6 +1297,10 @@ static struct attribute *adt7470_attrs[] = {
   	&sensor_dev_attr_pwm2.dev_attr.attr,
   	&sensor_dev_attr_pwm3.dev_attr.attr,
   	&sensor_dev_attr_pwm4.dev_attr.attr,
+	&sensor_dev_attr_pwm1_invert.dev_attr.attr,
+	&sensor_dev_attr_pwm2_invert.dev_attr.attr,
+	&sensor_dev_attr_pwm3_invert.dev_attr.attr,
+	&sensor_dev_attr_pwm4_invert.dev_attr.attr,
   	&sensor_dev_attr_pwm1_auto_point1_pwm.dev_attr.attr,
   	&sensor_dev_attr_pwm2_auto_point1_pwm.dev_attr.attr,
   	&sensor_dev_attr_pwm3_auto_point1_pwm.dev_attr.attr,








