Use the DTS property #pwm-cells to determine if the PWM controller needs
to enable the WDT reload feature, which changes the duty cycle to a
preprogrammed value after a WDT/EXTRST#. When #pwm-cells = <4>, the
feature will be enabled, and the PWM consumer can use the 4th argument to
set the reload duty cycle [0-255].

Signed-off-by: Billy Tsai <billy_tsai@aspeedtech.com>
Change-Id: Ided520f73220581e3b37819a106ec81ebf9bb5a6
---
 drivers/hwmon/aspeed-g6-pwm-tach.c | 49 ++++++++++++++++++++++++++++++
 drivers/pwm/core.c                 |  6 ++--
 include/linux/pwm.h                | 10 ++++++
 3 files changed, 62 insertions(+), 3 deletions(-)

diff --git a/drivers/hwmon/aspeed-g6-pwm-tach.c b/drivers/hwmon/aspeed-g6-pwm-tach.c
index 75eadda738ab..df47f9aa8ee6 100644
--- a/drivers/hwmon/aspeed-g6-pwm-tach.c
+++ b/drivers/hwmon/aspeed-g6-pwm-tach.c
@@ -56,6 +56,7 @@
 #include <linux/of_platform.h>
 #include <linux/platform_device.h>
 #include <linux/pwm.h>
+#include <dt-bindings/pwm/pwm.h>
 #include <linux/reset.h>
 #include <linux/sysfs.h>
 
@@ -452,6 +453,51 @@ static void aspeed_pwm_tach_reset_assert(void *data)
 	reset_control_assert(rst);
 }
 
+static void aspeed_pwm_set_wdt_reload(struct pwm_chip *chip,
+				      struct pwm_device *pwm,
+				      u64 reload_duty_cycle)
+{
+	struct aspeed_pwm_tach_data *priv = aspeed_pwm_chip_to_data(chip);
+	u32 hwpwm = pwm->hwpwm, val;
+
+	val = readl(priv->base + PWM_ASPEED_DUTY_CYCLE(hwpwm));
+	val &= ~PWM_ASPEED_DUTY_CYCLE_POINT_AS_WDT;
+	val |= FIELD_PREP(PWM_ASPEED_DUTY_CYCLE_POINT_AS_WDT,
+			  reload_duty_cycle);
+	writel(val, priv->base + PWM_ASPEED_DUTY_CYCLE(hwpwm));
+
+	val = readl(priv->base + PWM_ASPEED_CTRL(hwpwm));
+	val |= PWM_ASPEED_CTRL_DUTY_LOAD_AS_WDT_ENABLE;
+	writel(val, priv->base + PWM_ASPEED_CTRL(hwpwm));
+}
+
+static struct pwm_device *
+aspeed_pwm_xlate(struct pwm_chip *chip, const struct of_phandle_args *args)
+{
+	struct pwm_device *pwm;
+
+	/* flags in the fourth cell are optional */
+	if (args->args_count < 3)
+		return ERR_PTR(-EINVAL);
+
+	if (args->args[0] >= chip->npwm)
+		return ERR_PTR(-EINVAL);
+
+	pwm = pwm_request_from_chip(chip, args->args[0], NULL);
+	if (IS_ERR(pwm))
+		return pwm;
+
+	pwm->args.period = args->args[1];
+	pwm->args.polarity = PWM_POLARITY_NORMAL;
+	if (args->args[2] & PWM_POLARITY_INVERTED)
+		pwm->args.polarity = PWM_POLARITY_INVERSED;
+
+	if (args->args_count > 3 && args->args[3] < U8_MAX)
+		aspeed_pwm_set_wdt_reload(chip, pwm, args->args[3]);
+
+	return pwm;
+}
+
 static int aspeed_pwm_tach_probe(struct platform_device *pdev)
 {
 	struct device *dev = &pdev->dev, *hwmon;
@@ -493,6 +539,9 @@ static int aspeed_pwm_tach_probe(struct platform_device *pdev)
 	pwmchip_set_drvdata(chip, priv);
 	chip->ops = &aspeed_pwm_ops;
 
+	if (IS_ENABLED(CONFIG_OF))
+		chip->of_xlate = aspeed_pwm_xlate;
+
 	ret = devm_pwmchip_add(dev, chip);
 	if (ret)
 		return dev_err_probe(dev, ret, "Failed to add PWM chip\n");
diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c
index 6e752e148b98..8251f7b361ab 100644
--- a/drivers/pwm/core.c
+++ b/drivers/pwm/core.c
@@ -422,9 +422,8 @@ static int pwm_device_request(struct pwm_device *pwm, const char *label)
  * chip. A negative error code is returned if the index is not valid for the
  * specified PWM chip or if the PWM device cannot be requested.
  */
-static struct pwm_device *pwm_request_from_chip(struct pwm_chip *chip,
-						unsigned int index,
-						const char *label)
+struct pwm_device *pwm_request_from_chip(struct pwm_chip *chip,
+					 unsigned int index, const char *label)
 {
 	struct pwm_device *pwm;
 	int err;
@@ -442,6 +441,7 @@ static struct pwm_device *pwm_request_from_chip(struct pwm_chip *chip,
 
 	return pwm;
 }
+EXPORT_SYMBOL_GPL(pwm_request_from_chip);
 
 struct pwm_device *
 of_pwm_xlate_with_flags(struct pwm_chip *chip, const struct of_phandle_args *args)
diff --git a/include/linux/pwm.h b/include/linux/pwm.h
index 8acd60b53f58..95ae885f65c3 100644
--- a/include/linux/pwm.h
+++ b/include/linux/pwm.h
@@ -405,6 +405,8 @@ void pwmchip_remove(struct pwm_chip *chip);
 int __devm_pwmchip_add(struct device *dev, struct pwm_chip *chip, struct module *owner);
 #define devm_pwmchip_add(dev, chip) __devm_pwmchip_add(dev, chip, THIS_MODULE)
 
+struct pwm_device *pwm_request_from_chip(struct pwm_chip *chip,
+					 unsigned int index, const char *label);
 struct pwm_device *of_pwm_xlate_with_flags(struct pwm_chip *chip,
 		const struct of_phandle_args *args);
 struct pwm_device *of_pwm_single_xlate(struct pwm_chip *chip,
@@ -504,6 +506,14 @@ static inline void pwm_put(struct pwm_device *pwm)
 	might_sleep();
 }
 
+static inline struct pwm_device *pwm_request_from_chip(struct pwm_chip *chip,
+						       unsigned int index,
+						       const char *label)
+{
+	might_sleep();
+	return ERR_PTR(-ENODEV);
+}
+
 static inline struct pwm_device *devm_pwm_get(struct device *dev,
 					      const char *consumer)
 {
-- 
2.25.1