dm: gpio: Add a native driver model API

So far driver model's GPIO uclass just implements the existing GPIO API.
This has some limitations:

- it requires manual device tree munging to support GPIOs in device tree
    (fdtdec_get_gpio() and friends)
- it does not understand polarity
- it is somewhat slower since we must scan for the GPIO device each time
- Global GPIO numbering can change if other GPIO drivers are probed
- it requires extra steps to set the GPIO direction and value

The new functions have a dm_ prefix where necessary to avoid name conflicts
but we can remove that when it is no-longer needed. The new struct gpio_desc
holds all required information about the GPIO. For now this is intended to
be stored by the client requesting the GPIO, but in future it might be
brought into the uclass in some way.

With these changes the old GPIO API still works, and uses the driver model
API underneath.

Signed-off-by: Simon Glass <sjg@chromium.org>

2 files changed, 163 insertions, 71 deletions

diff --git a/drivers/gpio/gpio-uclass.c b/drivers/gpio/gpio-uclass.c
index 255700a..2f3c36b 100644
--- a/drivers/gpio/gpio-uclass.c
+++ b/drivers/gpio/gpio-uclass.c
@@ -13,14 +13,16 @@
 
 /**
  * gpio_to_device() - Convert global GPIO number to device, number
- * gpio:	The numeric representation of the GPIO
  *
  * Convert the GPIO number to an entry in the list of GPIOs
  * or GPIO blocks registered with the GPIO controller. Returns
  * entry on success, NULL on error.
+ *
+ * @gpio:	The numeric representation of the GPIO
+ * @desc:	Returns description (desc->flags will always be 0)
+ * @return 0 if found, -ENOENT if not found
  */
-static int gpio_to_device(unsigned int gpio, struct udevice **devp,
-			  unsigned int *offset)
+static int gpio_to_device(unsigned int gpio, struct gpio_desc *desc)
 {
 	struct gpio_dev_priv *uc_priv;
 	struct udevice *dev;
@@ -32,14 +34,15 @@ static int gpio_to_device(unsigned int gpio, struct udevice **devp,
 		uc_priv = dev->uclass_priv;
 		if (gpio >= uc_priv->gpio_base &&
 		    gpio < uc_priv->gpio_base + uc_priv->gpio_count) {
-			*devp = dev;
-			*offset = gpio - uc_priv->gpio_base;
+			desc->dev = dev;
+			desc->offset = gpio - uc_priv->gpio_base;
+			desc->flags = 0;
 			return 0;
 		}
 	}
 
 	/* No such GPIO */
-	return ret ? ret : -EINVAL;
+	return ret ? ret : -ENOENT;
 }
 
 int gpio_lookup_name(const char *name, struct udevice **devp,
@@ -88,6 +91,31 @@ int gpio_lookup_name(const char *name, struct udevice **devp,
 	return 0;
 }
 
+static int dm_gpio_request(struct gpio_desc *desc, const char *label)
+{
+	struct udevice *dev = desc->dev;
+	struct gpio_dev_priv *uc_priv;
+	char *str;
+	int ret;
+
+	uc_priv = dev->uclass_priv;
+	if (uc_priv->name[desc->offset])
+		return -EBUSY;
+	str = strdup(label);
+	if (!str)
+		return -ENOMEM;
+	if (gpio_get_ops(dev)->request) {
+		ret = gpio_get_ops(dev)->request(dev, desc->offset, label);
+		if (ret) {
+			free(str);
+			return ret;
+		}
+	}
+	uc_priv->name[desc->offset] = str;
+
+	return 0;
+}
+
 /**
  * gpio_request() - [COMPAT] Request GPIO
  * gpio:	GPIO number
@@ -102,32 +130,14 @@ int gpio_lookup_name(const char *name, struct udevice **devp,
  */
 int gpio_request(unsigned gpio, const char *label)
 {
-	struct gpio_dev_priv *uc_priv;
-	unsigned int offset;
-	struct udevice *dev;
-	char *str;
+	struct gpio_desc desc;
 	int ret;
 
-	ret = gpio_to_device(gpio, &dev, &offset);
+	ret = gpio_to_device(gpio, &desc);
 	if (ret)
 		return ret;
 
-	uc_priv = dev->uclass_priv;
-	if (uc_priv->name[offset])
-		return -EBUSY;
-	str = strdup(label);
-	if (!str)
-		return -ENOMEM;
-	if (gpio_get_ops(dev)->request) {
-		ret = gpio_get_ops(dev)->request(dev, offset, label);
-		if (ret) {
-			free(str);
-			return ret;
-		}
-	}
-	uc_priv->name[offset] = str;
-
-	return 0;
+	return dm_gpio_request(&desc, label);
 }
 
 /**
@@ -151,25 +161,11 @@ int gpio_requestf(unsigned gpio, const char *fmt, ...)
 	return gpio_request(gpio, buf);
 }
 
-/**
- * gpio_free() - [COMPAT] Relinquish GPIO
- * gpio:	GPIO number
- *
- * This function implements the API that's compatible with current
- * GPIO API used in U-Boot. The request is forwarded to particular
- * GPIO driver. Returns 0 on success, negative value on error.
- */
-int gpio_free(unsigned gpio)
+int _dm_gpio_free(struct udevice *dev, uint offset)
 {
 	struct gpio_dev_priv *uc_priv;
-	unsigned int offset;
-	struct udevice *dev;
 	int ret;
 
-	ret = gpio_to_device(gpio, &dev, &offset);
-	if (ret)
-		return ret;
-
 	uc_priv = dev->uclass_priv;
 	if (!uc_priv->name[offset])
 		return -ENXIO;
@@ -185,15 +181,35 @@ int gpio_free(unsigned gpio)
 	return 0;
 }
 
-static int check_reserved(struct udevice *dev, unsigned offset,
-			  const char *func)
+/**
+ * gpio_free() - [COMPAT] Relinquish GPIO
+ * gpio:	GPIO number
+ *
+ * This function implements the API that's compatible with current
+ * GPIO API used in U-Boot. The request is forwarded to particular
+ * GPIO driver. Returns 0 on success, negative value on error.
+ */
+int gpio_free(unsigned gpio)
 {
-	struct gpio_dev_priv *uc_priv = dev->uclass_priv;
+	struct gpio_desc desc;
+	int ret;
+
+	ret = gpio_to_device(gpio, &desc);
+	if (ret)
+		return ret;
+
+	return _dm_gpio_free(desc.dev, desc.offset);
+}
 
-	if (!uc_priv->name[offset]) {
+static int check_reserved(struct gpio_desc *desc, const char *func)
+{
+	struct gpio_dev_priv *uc_priv = desc->dev->uclass_priv;
+
+	if (!uc_priv->name[desc->offset]) {
 		printf("%s: %s: error: gpio %s%d not reserved\n",
-		       dev->name, func,
-		       uc_priv->bank_name ? uc_priv->bank_name : "", offset);
+		       desc->dev->name, func,
+		       uc_priv->bank_name ? uc_priv->bank_name : "",
+		       desc->offset);
 		return -EBUSY;
 	}
 
@@ -210,16 +226,17 @@ static int check_reserved(struct udevice *dev, unsigned offset,
  */
 int gpio_direction_input(unsigned gpio)
 {
-	unsigned int offset;
-	struct udevice *dev;
+	struct gpio_desc desc;
 	int ret;
 
-	ret = gpio_to_device(gpio, &dev, &offset);
+	ret = gpio_to_device(gpio, &desc);
+	if (ret)
+		return ret;
+	ret = check_reserved(&desc, "dir_input");
 	if (ret)
 		return ret;
-	ret = check_reserved(dev, offset, "dir_input");
 
-	return ret ? ret : gpio_get_ops(dev)->direction_input(dev, offset);
+	return gpio_get_ops(desc.dev)->direction_input(desc.dev, desc.offset);
 }
 
 /**
@@ -233,17 +250,81 @@ int gpio_direction_input(unsigned gpio)
  */
 int gpio_direction_output(unsigned gpio, int value)
 {
-	unsigned int offset;
-	struct udevice *dev;
+	struct gpio_desc desc;
 	int ret;
 
-	ret = gpio_to_device(gpio, &dev, &offset);
+	ret = gpio_to_device(gpio, &desc);
+	if (ret)
+		return ret;
+	ret = check_reserved(&desc, "dir_output");
+	if (ret)
+		return ret;
+
+	return gpio_get_ops(desc.dev)->direction_output(desc.dev,
+							desc.offset, value);
+}
+
+int dm_gpio_get_value(struct gpio_desc *desc)
+{
+	int value;
+	int ret;
+
+	ret = check_reserved(desc, "get_value");
 	if (ret)
 		return ret;
-	ret = check_reserved(dev, offset, "dir_output");
 
-	return ret ? ret :
-		gpio_get_ops(dev)->direction_output(dev, offset, value);
+	value = gpio_get_ops(desc->dev)->get_value(desc->dev, desc->offset);
+
+	return desc->flags & GPIOD_ACTIVE_LOW ? !value : value;
+}
+
+int dm_gpio_set_value(struct gpio_desc *desc, int value)
+{
+	int ret;
+
+	ret = check_reserved(desc, "set_value");
+	if (ret)
+		return ret;
+
+	if (desc->flags & GPIOD_ACTIVE_LOW)
+		value = !value;
+	gpio_get_ops(desc->dev)->set_value(desc->dev, desc->offset, value);
+	return 0;
+}
+
+int dm_gpio_set_dir_flags(struct gpio_desc *desc, ulong flags)
+{
+	struct udevice *dev = desc->dev;
+	struct dm_gpio_ops *ops = gpio_get_ops(dev);
+	int ret;
+
+	ret = check_reserved(desc, "set_dir");
+	if (ret)
+		return ret;
+
+	if (flags & GPIOD_IS_OUT) {
+		int value = flags & GPIOD_IS_OUT_ACTIVE ? 1 : 0;
+
+		if (flags & GPIOD_ACTIVE_LOW)
+			value = !value;
+		ret = ops->direction_output(dev, desc->offset, value);
+	} else  if (flags & GPIOD_IS_IN) {
+		ret = ops->direction_input(dev, desc->offset);
+	}
+	if (ret)
+		return ret;
+	/*
+	 * Update desc->flags here, so that GPIO_ACTIVE_LOW is honoured in
+	 * futures
+	 */
+	desc->flags = flags;
+
+	return 0;
+}
+
+int dm_gpio_set_dir(struct gpio_desc *desc)
+{
+	return dm_gpio_set_dir_flags(desc, desc->flags);
 }
 
 /**
@@ -257,16 +338,14 @@ int gpio_direction_output(unsigned gpio, int value)
  */
 int gpio_get_value(unsigned gpio)
 {
-	unsigned int offset;
-	struct udevice *dev;
 	int ret;
 
-	ret = gpio_to_device(gpio, &dev, &offset);
+	struct gpio_desc desc;
+
+	ret = gpio_to_device(gpio, &desc);
 	if (ret)
 		return ret;
-	ret = check_reserved(dev, offset, "get_value");
-
-	return ret ? ret : gpio_get_ops(dev)->get_value(dev, offset);
+	return dm_gpio_get_value(&desc);
 }
 
 /**
@@ -280,16 +359,13 @@ int gpio_get_value(unsigned gpio)
  */
 int gpio_set_value(unsigned gpio, int value)
 {
-	unsigned int offset;
-	struct udevice *dev;
+	struct gpio_desc desc;
 	int ret;
 
-	ret = gpio_to_device(gpio, &dev, &offset);
+	ret = gpio_to_device(gpio, &desc);
 	if (ret)
 		return ret;
-	ret = check_reserved(dev, offset, "set_value");
-
-	return ret ? ret : gpio_get_ops(dev)->set_value(dev, offset, value);
+	return dm_gpio_set_value(&desc, value);
 }
 
 const char *gpio_get_bank_info(struct udevice *dev, int *bit_count)
diff --git a/include/asm-generic/gpio.h b/include/asm-generic/gpio.h
index 36a36c6..a827a56 100644
--- a/include/asm-generic/gpio.h
+++ b/include/asm-generic/gpio.h
@@ -95,6 +95,22 @@ enum gpio_func_t {
 
 struct udevice;
 
+struct gpio_desc {
+	struct udevice *dev;	/* Device, NULL for invalid GPIO */
+	unsigned long flags;
+#define GPIOD_REQUESTED		(1 << 0)	/* Requested/claimed */
+#define GPIOD_IS_OUT		(1 << 1)	/* GPIO is an output */
+#define GPIOD_IS_IN		(1 << 2)	/* GPIO is an output */
+#define GPIOD_ACTIVE_LOW	(1 << 3)	/* value has active low */
+#define GPIOD_IS_OUT_ACTIVE	(1 << 4)	/* set output active */
+
+	uint offset;		/* GPIO offset within the device */
+	/*
+	 * We could consider adding the GPIO label in here. Possibly we could
+	 * use this structure for internal GPIO information.
+	 */
+};
+
 /**
  * gpio_get_status() - get the current GPIO status as a string
  *