reset: Add support for shared reset controls

In some SoCs some hw-blocks share a reset control. Add support for this
setup by adding new:

reset_control_get_shared()
devm_reset_control_get_shared()
devm_reset_control_get_shared_by_index()

methods to get a reset_control. Note that this patch omits adding of_
variants, if these are needed later they can be easily added.

This patch also changes the behavior of the existing exclusive
reset_control_get() variants, if these are now called more then once
for the same reset_control they will return -EBUSY. To catch existing
drivers triggering this error (there should not be any) a WARN_ON(1)
is added in this path.

When a reset_control is shared, the behavior of reset_control_assert /
deassert is changed, for shared reset_controls these will work like the
clock-enable/disable and regulator-on/off functions. They will keep a
deassert_count, and only (re-)assert the reset after reset_control_assert
has been called as many times as reset_control_deassert was called.

Calling reset_control_assert without first calling reset_control_deassert
is not allowed on a shared reset control. Calling reset_control_reset is
also not allowed on a shared reset control.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>

1 files changed, 81 insertions, 15 deletions

diff --git a/include/linux/reset.h b/include/linux/reset.h
index 1bb69a29d6db..a552134a209e 100644
--- a/include/linux/reset.h
+++ b/include/linux/reset.h
@@ -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);
 }
@@ -78,11 +78,17 @@ 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
  *
  * Returns a struct reset_control or IS_ERR() condition containing errno.
+ * If this function is called more then once for the same reset_control it will
+ * return -EBUSY.
+ *
+ * See reset_control_get_shared for details on shared references to
+ * reset-controls.
  *
  * Use of id names is optional.
  */
@@ -92,17 +98,46 @@ 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.
+ * This function is intended for use with reset-controls which are shared
+ * between hardware-blocks.
+ *
+ * When a reset-control is shared, the behavior of reset_control_assert /
+ * deassert is changed, the reset-core will keep track of a deassert_count
+ * and only (re-)assert the reset after reset_control_assert has been called
+ * as many times as reset_control_deassert was called. Also see the remark
+ * about shared reset-controls in the reset_control_assert docs.
+ *
+ * Calling reset_control_assert without first calling reset_control_deassert
+ * is not allowed on a shared reset control. Calling reset_control_reset is
+ * also not allowed on a shared reset control.
+ *
+ * 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 +148,12 @@ 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 +164,7 @@ 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 +182,13 @@ 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 +203,38 @@ 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