pwm: Allow chips to support multiple PWMs

Many PWM controllers provide access to more than a single PWM output and
may even share some resource among them. Allowing a PWM chip to provide
multiple PWM devices enables better sharing of those resources. As a
side-effect this change allows easy integration with the device tree
where a given PWM can be looked up based on the PWM chip's phandle and a
corresponding index.

This commit modifies the PWM core to support multiple PWMs per struct
pwm_chip. It achieves this in a similar way to how gpiolib works, by
allowing PWM ranges to be requested dynamically (pwm_chip.base == -1) or
starting at a given offset (pwm_chip.base >= 0). A chip specifies how
many PWMs it controls using the npwm member. Each of the functions in
the pwm_ops structure gets an additional argument that specified the PWM
number (it can be converted to a per-chip index by subtracting the
chip's base).

The total maximum number of PWM devices is currently fixed to 1024 while
the data is actually stored in a radix tree, thus saving resources if
not all of them are used.

Reviewed-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Reviewed-by: Shawn Guo <shawn.guo@linaro.org>
[eric@eukrea.com: fix error handling in pwmchip_add]
Signed-off-by: Eric Bénard <eric@eukrea.com>
Signed-off-by: Thierry Reding <thierry.reding@avionic-design.de>

1 files changed, 58 insertions, 13 deletions

diff --git a/include/linux/pwm.h b/include/linux/pwm.h
index 1f308a13105f..57103911f4c7 100644
--- a/include/linux/pwm.h
+++ b/include/linux/pwm.h
@@ -31,6 +31,33 @@ void pwm_disable(struct pwm_device *pwm);
 #ifdef CONFIG_PWM
 struct pwm_chip;
 
+enum {
+	PWMF_REQUESTED = 1 << 0,
+	PWMF_ENABLED = 1 << 1,
+};
+
+struct pwm_device {
+	const char		*label;
+	unsigned long		flags;
+	unsigned int		hwpwm;
+	unsigned int		pwm;
+	struct pwm_chip		*chip;
+	void			*chip_data;
+
+	unsigned int		period; /* in nanoseconds */
+};
+
+static inline void pwm_set_period(struct pwm_device *pwm, unsigned int period)
+{
+	if (pwm)
+		pwm->period = period;
+}
+
+static inline unsigned int pwm_get_period(struct pwm_device *pwm)
+{
+	return pwm ? pwm->period : 0;
+}
+
 /**
  * struct pwm_ops - PWM controller operations
  * @request: optional hook for requesting a PWM
@@ -41,29 +68,47 @@ struct pwm_chip;
  * @owner: helps prevent removal of modules exporting active PWMs
  */
 struct pwm_ops {
-	int			(*request)(struct pwm_chip *chip);
-	void			(*free)(struct pwm_chip *chip);
-	int			(*config)(struct pwm_chip *chip, int duty_ns,
-						int period_ns);
-	int			(*enable)(struct pwm_chip *chip);
-	void			(*disable)(struct pwm_chip *chip);
+	int			(*request)(struct pwm_chip *chip,
+					   struct pwm_device *pwm);
+	void			(*free)(struct pwm_chip *chip,
+					struct pwm_device *pwm);
+	int			(*config)(struct pwm_chip *chip,
+					  struct pwm_device *pwm,
+					  int duty_ns, int period_ns);
+	int			(*enable)(struct pwm_chip *chip,
+					  struct pwm_device *pwm);
+	void			(*disable)(struct pwm_chip *chip,
+					   struct pwm_device *pwm);
 	struct module		*owner;
 };
 
 /**
- * struct pwm_chip - abstract a PWM
- * @pwm_id: global PWM device index
- * @label: PWM device label
- * @ops: controller operations
+ * struct pwm_chip - abstract a PWM controller
+ * @dev: device providing the PWMs
+ * @list: list node for internal use
+ * @ops: callbacks for this PWM controller
+ * @base: number of first PWM controlled by this chip
+ * @npwm: number of PWMs controlled by this chip
+ * @pwms: array of PWM devices allocated by the framework
  */
 struct pwm_chip {
-	int			pwm_id;
-	const char		*label;
-	struct pwm_ops		*ops;
+	struct device		*dev;
+	struct list_head	list;
+	const struct pwm_ops	*ops;
+	int			base;
+	unsigned int		npwm;
+
+	struct pwm_device	*pwms;
 };
 
+int pwm_set_chip_data(struct pwm_device *pwm, void *data);
+void *pwm_get_chip_data(struct pwm_device *pwm);
+
 int pwmchip_add(struct pwm_chip *chip);
 int pwmchip_remove(struct pwm_chip *chip);
+struct pwm_device *pwm_request_from_chip(struct pwm_chip *chip,
+					 unsigned int index,
+					 const char *label);
 #endif
 
 #endif /* __LINUX_PWM_H */