[PATCH v3 3/3] reset: Add support for shared reset controls

@@ -8,6 +8,7 @@
  * the Free Software Foundation; either version 2 of the License, or
  * (at your option) any later version.
  */
+#include <linux/atomic.h>
 #include <linux/device.h>
 #include <linux/err.h>
 #include <linux/export.h>

@@ -29,12 +30,16 @@ static LIST_HEAD(reset_controller_list);
  * @id: ID of the reset controller in the reset
  *      controller device
  * @refcnt: Number of gets of this reset_control
+ * @shared: Is this a shared (1), or an exclusive (0) reset_control?
+ * @deassert_cnt: Number of times this reset line has been deasserted
  */
 struct reset_control {
 	struct reset_controller_dev *rcdev;
 	struct list_head list;
 	unsigned int id;
 	unsigned int refcnt;
+	int shared;
+	atomic_t deassert_count;
 };
 
 /**

@@ -94,9 +99,16 @@ EXPORT_SYMBOL_GPL(reset_controller_unregister);
 /**
  * reset_control_reset - reset the controlled device
  * @rstc: reset controller
+ *
+ * Calling this on a shared reset controller is an error.
  */
 int reset_control_reset(struct reset_control *rstc)
 {
+	if (rstc->shared) {
+		WARN_ON(1);
+		return -EINVAL;
+	}
+
 	if (rstc->rcdev->ops->reset)
 		return rstc->rcdev->ops->reset(rstc->rcdev, rstc->id);
 

@@ -107,26 +119,47 @@ EXPORT_SYMBOL_GPL(reset_control_reset);
 /**
  * reset_control_assert - asserts the reset line
  * @rstc: reset controller
+ *
+ * Calling this on an exclusive reset controller guarantees that the reset
+ * will be asserted. When called on a shared reset controller the line may
+ * still be deasserted, as long as other users keep it so.
  */
 int reset_control_assert(struct reset_control *rstc)
 {
-	if (rstc->rcdev->ops->assert)
-		return rstc->rcdev->ops->assert(rstc->rcdev, rstc->id);
+	if (!rstc->rcdev->ops->assert)
+		return -ENOTSUPP;
 
-	return -ENOTSUPP;
+	if (rstc->shared) {
+		if (atomic_read(&rstc->deassert_count) == 0) {
+			WARN_ON(1);
+			return -EINVAL;
+		}
+
+		if (atomic_dec_return(&rstc->deassert_count) != 0)
+			return 0;
+	}
+
+	return rstc->rcdev->ops->assert(rstc->rcdev, rstc->id);
 }
 EXPORT_SYMBOL_GPL(reset_control_assert);
 
 /**
  * reset_control_deassert - deasserts the reset line
  * @rstc: reset controller
+ *
+ * After calling this function, the reset is guaranteed to be deasserted.
  */
 int reset_control_deassert(struct reset_control *rstc)
 {
-	if (rstc->rcdev->ops->deassert)
-		return rstc->rcdev->ops->deassert(rstc->rcdev, rstc->id);
+	if (!rstc->rcdev->ops->deassert)
+		return -ENOTSUPP;
 
-	return -ENOTSUPP;
+	if (rstc->shared) {
+		if (atomic_inc_return(&rstc->deassert_count) != 1)
+			return 0;
+	}
+
+	return rstc->rcdev->ops->deassert(rstc->rcdev, rstc->id);
 }
 EXPORT_SYMBOL_GPL(reset_control_deassert);
 

@@ -147,7 +180,7 @@ EXPORT_SYMBOL_GPL(reset_control_status);
 
 static struct reset_control *__reset_control_get(
 				struct reset_controller_dev *rcdev,
-				unsigned int index)
+				unsigned int index, int shared)
 {
 	struct reset_control *rstc;
 

@@ -155,6 +188,10 @@ static struct reset_control *__reset_control_get(
 
 	list_for_each_entry(rstc, &rcdev->reset_control_head, list) {
 		if (rstc->id == index) {
+			if (!rstc->shared || !shared) {
+				WARN_ON(1);
+				return ERR_PTR(-EBUSY);
+			}
 			rstc->refcnt++;
 			return rstc;
 		}

@@ -170,6 +207,7 @@ static struct reset_control *__reset_control_get(
 	list_add(&rstc->list, &rcdev->reset_control_head);
 	rstc->id = index;
 	rstc->refcnt = 1;
+	rstc->shared = shared;
 
 	return rstc;
 }

@@ -188,7 +226,7 @@ static void __reset_control_put(struct reset_control *rstc)
 }
 
 struct reset_control *__of_reset_control_get(struct device_node *node,
-					     const char *id, int index)
+				     const char *id, int index, int shared)
 {
 	struct reset_control *rstc = ERR_PTR(-EPROBE_DEFER);
 	struct reset_controller_dev *r, *rcdev;

@@ -233,7 +271,7 @@ struct reset_control *__of_reset_control_get(struct device_node *node,
 	}
 
 	/* reset_list_mutex also protects the rcdev's reset_control list */
-	rstc = __reset_control_get(rcdev, rstc_id);
+	rstc = __reset_control_get(rcdev, rstc_id, shared);
 
 	mutex_unlock(&reset_list_mutex);
 

@@ -263,7 +301,7 @@ static void devm_reset_control_release(struct device *dev, void *res)
 }
 
 struct reset_control *__devm_reset_control_get(struct device *dev,
-					       const char *id, int index)
+				     const char *id, int index, int shared)
 {
 	struct reset_control **ptr, *rstc;
 

@@ -272,7 +310,8 @@ struct reset_control *__devm_reset_control_get(struct device *dev,
 	if (!ptr)
 		return ERR_PTR(-ENOMEM);
 
-	rstc = __of_reset_control_get(dev ? dev->of_node : NULL, id, index);
+	rstc = __of_reset_control_get(dev ? dev->of_node : NULL,
+				      id, index, shared);
 	if (!IS_ERR(rstc)) {
 		*ptr = rstc;
 		devres_add(dev, ptr);

@@ -13,10 +13,10 @@ int reset_control_deassert(struct reset_control *rstc);
 int reset_control_status(struct reset_control *rstc);
 
 struct reset_control *__of_reset_control_get(struct device_node *node,
-					     const char *id, int index);
+				     const char *id, int index, int shared);
 void reset_control_put(struct reset_control *rstc);
 struct reset_control *__devm_reset_control_get(struct device *dev,
-					       const char *id, int index);
+				     const char *id, int index, int shared);
 
 int __must_check device_reset(struct device *dev);
 

@@ -63,14 +63,14 @@ static inline int device_reset_optional(struct device *dev)
 
 static inline struct reset_control *__of_reset_control_get(
 					struct device_node *node,
-					const char *id, int index)
+					const char *id, int index, int shared)
 {
 	return ERR_PTR(-EINVAL);
 }
 
 static inline struct reset_control *__devm_reset_control_get(
 					struct device *dev,
-					const char *id, int index)
+					const char *id, int index, int shared)
 {
 	return ERR_PTR(-EINVAL);
 }

@@ -78,7 +78,8 @@ static inline struct reset_control *__devm_reset_control_get(
 #endif /* CONFIG_RESET_CONTROLLER */
 
 /**
- * reset_control_get - Lookup and obtain a reference to a reset controller.
+ * reset_control_get - Lookup and obtain an exclusive reference to a
+ *                     reset controller.
  * @dev: device to be reset by the controller
  * @id: reset line name
  *

@@ -92,17 +93,34 @@ static inline struct reset_control *__must_check reset_control_get(
 #ifndef CONFIG_RESET_CONTROLLER
 	WARN_ON(1);
 #endif
-	return __of_reset_control_get(dev ? dev->of_node : NULL, id, 0);
+	return __of_reset_control_get(dev ? dev->of_node : NULL, id, 0, 0);
 }
 
 static inline struct reset_control *reset_control_get_optional(
 					struct device *dev, const char *id)
 {
-	return __of_reset_control_get(dev ? dev->of_node : NULL, id, 0);
+	return __of_reset_control_get(dev ? dev->of_node : NULL, id, 0, 0);
 }
 
 /**
- * of_reset_control_get - Lookup and obtain a reference to a reset controller.
+ * reset_control_get_shared - Lookup and obtain a shared reference to a
+ *                            reset controller.
+ * @dev: device to be reset by the controller
+ * @id: reset line name
+ *
+ * Returns a struct reset_control or IS_ERR() condition containing errno.
+ *
+ * Use of id names is optional.
+ */
+static inline struct reset_control *reset_control_get_shared(
+					struct device *dev, const char *id)
+{
+	return __of_reset_control_get(dev ? dev->of_node : NULL, id, 0, 1);
+}
+
+/**
+ * of_reset_control_get - Lookup and obtain an exclusive reference to a
+ *                        reset controller.
  * @node: device to be reset by the controller
  * @id: reset line name
  *

@@ -113,12 +131,12 @@ static inline struct reset_control *reset_control_get_optional(
 static inline struct reset_control *of_reset_control_get(
 				struct device_node *node, const char *id)
 {
-	return __of_reset_control_get(node, id, 0);
+	return __of_reset_control_get(node, id, 0, 0);
 }
 
 /**
- * of_reset_control_get_by_index - Lookup and obtain a reference to a reset
- * controller by index.
+ * of_reset_control_get_by_index - Lookup and obtain an exclusive reference to
+ *                                 a reset controller by index.
  * @node: device to be reset by the controller
  * @index: index of the reset controller
  *

@@ -129,7 +147,7 @@ static inline struct reset_control *of_reset_control_get(
 static inline struct reset_control *of_reset_control_get_by_index(
 					struct device_node *node, int index)
 {
-	return __of_reset_control_get(node, NULL, index);
+	return __of_reset_control_get(node, NULL, index, 0);
 }
 
 /**

@@ -147,13 +165,13 @@ static inline struct reset_control *__must_check devm_reset_control_get(
 #ifndef CONFIG_RESET_CONTROLLER
 	WARN_ON(1);
 #endif
-	return __devm_reset_control_get(dev, id, 0);
+	return __devm_reset_control_get(dev, id, 0, 0);
 }
 
 static inline struct reset_control *devm_reset_control_get_optional(
 					struct device *dev, const char *id)
 {
-	return __devm_reset_control_get(dev, id, 0);
+	return __devm_reset_control_get(dev, id, 0, 0);
 }
 
 /**

@@ -168,7 +186,38 @@ static inline struct reset_control *devm_reset_control_get_optional(
 static inline struct reset_control *devm_reset_control_get_by_index(
 					struct device *dev, int index)
 {
-	return __devm_reset_control_get(dev, NULL, index);
+	return __devm_reset_control_get(dev, NULL, index, 0);
+}
+
+/**
+ * devm_reset_control_get_shared - resource managed reset_control_get_shared()
+ * @dev: device to be reset by the controller
+ * @id: reset line name
+ *
+ * Managed reset_control_get_shared(). For reset controllers returned from
+ * this function, reset_control_put() is called automatically on driver detach.
+ * See reset_control_get_shared() for more information.
+ */
+static inline struct reset_control *devm_reset_control_get_shared(
+					struct device *dev, const char *id)
+{
+	return __devm_reset_control_get(dev, id, 0, 1);
+}
+
+/**
+ * devm_reset_control_get_shared_by_index - resource managed
+ * reset_control_get_shared
+ * @dev: device to be reset by the controller
+ * @index: index of the reset controller
+ *
+ * Managed reset_control_get_shared(). For reset controllers returned from
+ * this function, reset_control_put() is called automatically on driver detach.
+ * See reset_control_get_shared() for more information.
+ */
+static inline struct reset_control *devm_reset_control_get_shared_by_index(
+					struct device *dev, int index)
+{
+	return __devm_reset_control_get(dev, NULL, index, 1);
 }
 
 #endif