[PATCH v2 5/6] hwmon: (adt7470) Register as a PWM provider

[Luiz Angelo Daros de Luca <luizluca@gmail.com>]

hwmon: (adt7470) Register as a PWM provider

The ADT7470 features four PWM outputs that can be used to control fans.
Previously, these were only accessible through the legacy hwmon sysfs
interface.

Register the ADT7470 as a generic PWM provider. This enables standard
Device Tree PWM consumers, such as "pwm-fan", to use the device through
the "#pwm-cells" property.

When a PWM consumer applies a new PWM state, the driver automatically
switches the corresponding PWM channel to manual mode so that the
requested duty cycle takes effect. The duty cycle specified by the PWM
framework is internally converted to the 0-255 scale expected by the
hardware registers.

The legacy sysfs interface remains unaffected and operates in parallel.

Signed-off-by: Luiz Angelo Daros de Luca <luizluca@gmail.com>
---
 drivers/hwmon/Kconfig   |  1 +
 drivers/hwmon/adt7470.c | 67 +++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 68 insertions(+)

diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
index 08c29685126a..8838b6714e60 100644
--- a/drivers/hwmon/Kconfig
+++ b/drivers/hwmon/Kconfig
@@ -224,6 +224,7 @@ config SENSORS_ADT7462
 config SENSORS_ADT7470
 	tristate "Analog Devices ADT7470"
 	depends on I2C
+	depends on PWM || PWM=n
 	select REGMAP_I2C
 	help
 	  If you say yes here you get support for the Analog Devices
diff --git a/drivers/hwmon/adt7470.c b/drivers/hwmon/adt7470.c
index d881609c99aa..aaae14a421cd 100644
--- a/drivers/hwmon/adt7470.c
+++ b/drivers/hwmon/adt7470.c
@@ -22,6 +22,7 @@
 #include <linux/sched.h>
 #include <linux/slab.h>
 #include <linux/util_macros.h>
+#include <linux/pwm.h>
 
 /* Addresses to scan */
 static const unsigned short normal_i2c[] = { 0x2C, 0x2E, 0x2F, I2C_CLIENT_END };
@@ -864,6 +865,57 @@ static int adt7470_pwm_write(struct device *dev, u32 attr, int channel, long val
 	return err;
 }
 
+static int adt7470_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
+			     const struct pwm_state *state)
+{
+	struct adt7470_data *data = pwmchip_get_drvdata(chip);
+	unsigned int pwm_auto_reg_mask;
+	int err;
+	u8 val;
+
+	if (pwm->hwpwm % 2)
+		pwm_auto_reg_mask = ADT7470_PWM2_AUTO_MASK;
+	else
+		pwm_auto_reg_mask = ADT7470_PWM1_AUTO_MASK;
+
+	if (state->enabled && state->period > 0)
+		val = DIV_ROUND_CLOSEST_ULL(state->duty_cycle * 255, state->period);
+	else
+		val = 0;
+
+	mutex_lock(&data->lock);
+
+	if (data->pwm[pwm->hwpwm] == val &&
+	    data->pwm_automatic[pwm->hwpwm] == 0) {
+		mutex_unlock(&data->lock);
+		return 0;
+	}
+
+	/* Put the PWM channel in manual mode before updating it. */
+	err = regmap_update_bits(data->regmap,
+				 ADT7470_REG_PWM_CFG(pwm->hwpwm),
+				 pwm_auto_reg_mask, 0);
+	if (err < 0)
+		goto out;
+
+	data->pwm_automatic[pwm->hwpwm] = 0;
+
+	err = regmap_write(data->regmap,
+			   ADT7470_REG_PWM(pwm->hwpwm), val);
+	if (err < 0)
+		goto out;
+
+	data->pwm[pwm->hwpwm] = val;
+out:
+	mutex_unlock(&data->lock);
+
+	return err;
+}
+
+static const struct pwm_ops adt7470_pwm_ops = {
+	.apply = adt7470_pwm_apply,
+};
+
 static ssize_t pwm_max_show(struct device *dev,
 			    struct device_attribute *devattr, char *buf)
 {
@@ -1299,6 +1351,21 @@ static int adt7470_probe(struct i2c_client *client)
 	if (IS_ERR(hwmon_dev))
 		return PTR_ERR(hwmon_dev);
 
+	if (IS_REACHABLE(CONFIG_PWM)) {
+		struct pwm_chip *chip;
+
+		chip = devm_pwmchip_alloc(dev, ADT7470_PWM_COUNT, 0);
+		if (IS_ERR(chip))
+			return PTR_ERR(chip);
+
+		chip->ops = &adt7470_pwm_ops;
+		pwmchip_set_drvdata(chip, data);
+
+		err = devm_pwmchip_add(dev, chip);
+		if (err)
+			return dev_warn_probe(dev, err, "failed to register PWM chip\n");
+	}
+
 	data->auto_update = kthread_run(adt7470_update_thread, client, "%s",
 					dev_name(hwmon_dev));
 	if (IS_ERR(data->auto_update))

-- 
2.55.0