[PATCH v4 0/3] reset: Add support for shared reset controls

[PATCH v4 0/3] reset: Add support for shared reset controls

[Hans de Goede]

Hi All,

Here is v4 of my shared reset-controls patch.

Changes in v3:
-Rewrite as result of mailinglist discussions changing the API

Changes in v4:
-Improve documentation for shared reset-controls
-Move WARN_ON(foo) to inside if () conditions

Regards,

Hans

[PATCH v4 1/3] reset: Make [of_]reset_control_get[_foo] functions wrappers

[Hans de Goede]

With both the regular, _by_index and _optional variants we already have
quite a few variants of [of_]reset_control_get[_foo], the upcoming
addition of shared reset lines support makes this worse.

This commit changes all the variants into wrappers around common core
functions. For completeness sake this commit also adds a new
devm_get_reset_control_by_index wrapper.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
 drivers/reset/core.c  |  84 +++++++--------------------------
 include/linux/reset.h | 126 +++++++++++++++++++++++++++++++++++---------------
 2 files changed, 107 insertions(+), 103 deletions(-)

diff --git a/drivers/reset/core.c b/drivers/reset/core.c
index 8737663..f695429 100644
--- a/drivers/reset/core.c
+++ b/drivers/reset/core.c
@@ -139,18 +139,8 @@ int reset_control_status(struct reset_control *rstc)
 }
 EXPORT_SYMBOL_GPL(reset_control_status);
 
-/**
- * of_reset_control_get_by_index - Lookup and obtain a reference to a reset
- * controller by index.
- * @node: device to be reset by the controller
- * @index: index of the reset controller
- *
- * This is to be used to perform a list of resets for a device or power domain
- * in whatever order. Returns a struct reset_control or IS_ERR() condition
- * containing errno.
- */
-struct reset_control *of_reset_control_get_by_index(struct device_node *node,
-					   int index)
+struct reset_control *__of_reset_control_get(struct device_node *node,
+					     const char *id, int index)
 {
 	struct reset_control *rstc = ERR_PTR(-EPROBE_DEFER);
 	struct reset_controller_dev *r, *rcdev;
@@ -158,6 +148,16 @@ struct reset_control *of_reset_control_get_by_index(struct device_node *node,
 	int rstc_id;
 	int ret;
 
+	if (!node)
+		return ERR_PTR(-EINVAL);
+
+	if (id) {
+		index = of_property_match_string(node,
+						 "reset-names", id);
+		if (index < 0)
+			return ERR_PTR(-ENOENT);
+	}
+
 	ret = of_parse_phandle_with_args(node, "resets", "#reset-cells",
 					 index, &args);
 	if (ret)
@@ -198,49 +198,7 @@ struct reset_control *of_reset_control_get_by_index(struct device_node *node,
 
 	return rstc;
 }
-EXPORT_SYMBOL_GPL(of_reset_control_get_by_index);
-
-/**
- * of_reset_control_get - Lookup and obtain a reference to a reset controller.
- * @node: 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.
- */
-struct reset_control *of_reset_control_get(struct device_node *node,
-					   const char *id)
-{
-	int index = 0;
-
-	if (id) {
-		index = of_property_match_string(node,
-						 "reset-names", id);
-		if (index < 0)
-			return ERR_PTR(-ENOENT);
-	}
-	return of_reset_control_get_by_index(node, index);
-}
-EXPORT_SYMBOL_GPL(of_reset_control_get);
-
-/**
- * reset_control_get - Lookup and obtain a 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.
- */
-struct reset_control *reset_control_get(struct device *dev, const char *id)
-{
-	if (!dev)
-		return ERR_PTR(-EINVAL);
-
-	return of_reset_control_get(dev->of_node, id);
-}
-EXPORT_SYMBOL_GPL(reset_control_get);
+EXPORT_SYMBOL_GPL(__of_reset_control_get);
 
 /**
  * reset_control_put - free the reset controller
@@ -262,16 +220,8 @@ static void devm_reset_control_release(struct device *dev, void *res)
 	reset_control_put(*(struct reset_control **)res);
 }
 
-/**
- * devm_reset_control_get - resource managed reset_control_get()
- * @dev: device to be reset by the controller
- * @id: reset line name
- *
- * Managed reset_control_get(). For reset controllers returned from this
- * function, reset_control_put() is called automatically on driver detach.
- * See reset_control_get() for more information.
- */
-struct reset_control *devm_reset_control_get(struct device *dev, const char *id)
+struct reset_control *__devm_reset_control_get(struct device *dev,
+					       const char *id, int index)
 {
 	struct reset_control **ptr, *rstc;
 
@@ -280,7 +230,7 @@ struct reset_control *devm_reset_control_get(struct device *dev, const char *id)
 	if (!ptr)
 		return ERR_PTR(-ENOMEM);
 
-	rstc = reset_control_get(dev, id);
+	rstc = __of_reset_control_get(dev ? dev->of_node : NULL, id, index);
 	if (!IS_ERR(rstc)) {
 		*ptr = rstc;
 		devres_add(dev, ptr);
@@ -290,7 +240,7 @@ struct reset_control *devm_reset_control_get(struct device *dev, const char *id)
 
 	return rstc;
 }
-EXPORT_SYMBOL_GPL(devm_reset_control_get);
+EXPORT_SYMBOL_GPL(__devm_reset_control_get);
 
 /**
  * device_reset - find reset controller associated with the device
diff --git a/include/linux/reset.h b/include/linux/reset.h
index c4c097d..1bb69a2 100644
--- a/include/linux/reset.h
+++ b/include/linux/reset.h
@@ -1,8 +1,8 @@
 #ifndef _LINUX_RESET_H_
 #define _LINUX_RESET_H_
 
-struct device;
-struct device_node;
+#include <linux/device.h>
+
 struct reset_control;
 
 #ifdef CONFIG_RESET_CONTROLLER
@@ -12,9 +12,11 @@ int reset_control_assert(struct reset_control *rstc);
 int reset_control_deassert(struct reset_control *rstc);
 int reset_control_status(struct reset_control *rstc);
 
-struct reset_control *reset_control_get(struct device *dev, const char *id);
+struct reset_control *__of_reset_control_get(struct device_node *node,
+					     const char *id, int index);
 void reset_control_put(struct reset_control *rstc);
-struct reset_control *devm_reset_control_get(struct device *dev, const char *id);
+struct reset_control *__devm_reset_control_get(struct device *dev,
+					       const char *id, int index);
 
 int __must_check device_reset(struct device *dev);
 
@@ -23,24 +25,6 @@ static inline int device_reset_optional(struct device *dev)
 	return device_reset(dev);
 }
 
-static inline struct reset_control *reset_control_get_optional(
-					struct device *dev, const char *id)
-{
-	return reset_control_get(dev, id);
-}
-
-static inline struct reset_control *devm_reset_control_get_optional(
-					struct device *dev, const char *id)
-{
-	return devm_reset_control_get(dev, id);
-}
-
-struct reset_control *of_reset_control_get(struct device_node *node,
-					   const char *id);
-
-struct reset_control *of_reset_control_get_by_index(
-					struct device_node *node, int index);
-
 #else
 
 static inline int reset_control_reset(struct reset_control *rstc)
@@ -77,44 +61,114 @@ static inline int device_reset_optional(struct device *dev)
 	return -ENOTSUPP;
 }
 
-static inline struct reset_control *__must_check reset_control_get(
-					struct device *dev, const char *id)
+static inline struct reset_control *__of_reset_control_get(
+					struct device_node *node,
+					const char *id, int index)
 {
-	WARN_ON(1);
 	return ERR_PTR(-EINVAL);
 }
 
-static inline struct reset_control *__must_check devm_reset_control_get(
-					struct device *dev, const char *id)
+static inline struct reset_control *__devm_reset_control_get(
+					struct device *dev,
+					const char *id, int index)
 {
-	WARN_ON(1);
 	return ERR_PTR(-EINVAL);
 }
 
-static inline struct reset_control *reset_control_get_optional(
+#endif /* CONFIG_RESET_CONTROLLER */
+
+/**
+ * reset_control_get - Lookup and obtain a 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 *__must_check reset_control_get(
 					struct device *dev, const char *id)
 {
-	return ERR_PTR(-ENOTSUPP);
+#ifndef CONFIG_RESET_CONTROLLER
+	WARN_ON(1);
+#endif
+	return __of_reset_control_get(dev ? dev->of_node : NULL, id, 0);
 }
 
-static inline struct reset_control *devm_reset_control_get_optional(
+static inline struct reset_control *reset_control_get_optional(
 					struct device *dev, const char *id)
 {
-	return ERR_PTR(-ENOTSUPP);
+	return __of_reset_control_get(dev ? dev->of_node : NULL, id, 0);
 }
 
+/**
+ * of_reset_control_get - Lookup and obtain a reference to a reset controller.
+ * @node: 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 *of_reset_control_get(
 				struct device_node *node, const char *id)
 {
-	return ERR_PTR(-ENOTSUPP);
+	return __of_reset_control_get(node, id, 0);
 }
 
+/**
+ * of_reset_control_get_by_index - Lookup and obtain a reference to a reset
+ * controller by index.
+ * @node: device to be reset by the controller
+ * @index: index of the reset controller
+ *
+ * This is to be used to perform a list of resets for a device or power domain
+ * in whatever order. Returns a struct reset_control or IS_ERR() condition
+ * containing errno.
+ */
 static inline struct reset_control *of_reset_control_get_by_index(
-				struct device_node *node, int index)
+					struct device_node *node, int index)
 {
-	return ERR_PTR(-ENOTSUPP);
+	return __of_reset_control_get(node, NULL, index);
 }
 
-#endif /* CONFIG_RESET_CONTROLLER */
+/**
+ * devm_reset_control_get - resource managed reset_control_get()
+ * @dev: device to be reset by the controller
+ * @id: reset line name
+ *
+ * Managed reset_control_get(). For reset controllers returned from this
+ * function, reset_control_put() is called automatically on driver detach.
+ * See reset_control_get() for more information.
+ */
+static inline struct reset_control *__must_check devm_reset_control_get(
+					struct device *dev, const char *id)
+{
+#ifndef CONFIG_RESET_CONTROLLER
+	WARN_ON(1);
+#endif
+	return __devm_reset_control_get(dev, id, 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);
+}
+
+/**
+ * devm_reset_control_get_by_index - resource managed reset_control_get
+ * @dev: device to be reset by the controller
+ * @index: index of the reset controller
+ *
+ * Managed reset_control_get(). For reset controllers returned from this
+ * function, reset_control_put() is called automatically on driver detach.
+ * See reset_control_get() for more information.
+ */
+static inline struct reset_control *devm_reset_control_get_by_index(
+					struct device *dev, int index)
+{
+	return __devm_reset_control_get(dev, NULL, index);
+}
 
 #endif
-- 
2.7.1

[PATCH v4 2/3] reset: Share struct reset_control between reset_control_get calls

[Hans de Goede]

Now that struct reset_control no longer stores the device pointer for
the device calling reset_control_get we can share a single struct
reset_control when multiple calls to reset_control_get are made for
the same reset line (same id / index).

This is a preparation patch for adding support for shared reset lines.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
 drivers/reset/core.c             | 82 ++++++++++++++++++++++++++++++----------
 include/linux/reset-controller.h |  2 +
 2 files changed, 64 insertions(+), 20 deletions(-)

diff --git a/drivers/reset/core.c b/drivers/reset/core.c
index f695429..e439ae2 100644
--- a/drivers/reset/core.c
+++ b/drivers/reset/core.c
@@ -18,19 +18,23 @@
 #include <linux/reset-controller.h>
 #include <linux/slab.h>
 
-static DEFINE_MUTEX(reset_controller_list_mutex);
+static DEFINE_MUTEX(reset_list_mutex);
 static LIST_HEAD(reset_controller_list);
 
 /**
  * struct reset_control - a reset control
  * @rcdev: a pointer to the reset controller device
  *         this reset control belongs to
+ * @list: list entry for the rcdev's reset controller list
  * @id: ID of the reset controller in the reset
  *      controller device
+ * @refcnt: Number of gets of this reset_control
  */
 struct reset_control {
 	struct reset_controller_dev *rcdev;
+	struct list_head list;
 	unsigned int id;
+	unsigned int refcnt;
 };
 
 /**
@@ -65,9 +69,11 @@ int reset_controller_register(struct reset_controller_dev *rcdev)
 		rcdev->of_xlate = of_reset_simple_xlate;
 	}
 
-	mutex_lock(&reset_controller_list_mutex);
+	INIT_LIST_HEAD(&rcdev->reset_control_head);
+
+	mutex_lock(&reset_list_mutex);
 	list_add(&rcdev->list, &reset_controller_list);
-	mutex_unlock(&reset_controller_list_mutex);
+	mutex_unlock(&reset_list_mutex);
 
 	return 0;
 }
@@ -79,9 +85,9 @@ EXPORT_SYMBOL_GPL(reset_controller_register);
  */
 void reset_controller_unregister(struct reset_controller_dev *rcdev)
 {
-	mutex_lock(&reset_controller_list_mutex);
+	mutex_lock(&reset_list_mutex);
 	list_del(&rcdev->list);
-	mutex_unlock(&reset_controller_list_mutex);
+	mutex_unlock(&reset_list_mutex);
 }
 EXPORT_SYMBOL_GPL(reset_controller_unregister);
 
@@ -139,6 +145,48 @@ int reset_control_status(struct reset_control *rstc)
 }
 EXPORT_SYMBOL_GPL(reset_control_status);
 
+static struct reset_control *__reset_control_get(
+				struct reset_controller_dev *rcdev,
+				unsigned int index)
+{
+	struct reset_control *rstc;
+
+	lockdep_assert_held(&reset_list_mutex);
+
+	list_for_each_entry(rstc, &rcdev->reset_control_head, list) {
+		if (rstc->id == index) {
+			rstc->refcnt++;
+			return rstc;
+		}
+	}
+
+	rstc = kzalloc(sizeof(*rstc), GFP_KERNEL);
+	if (!rstc)
+		return ERR_PTR(-ENOMEM);
+
+	try_module_get(rcdev->owner);
+
+	rstc->rcdev = rcdev;
+	list_add(&rstc->list, &rcdev->reset_control_head);
+	rstc->id = index;
+	rstc->refcnt = 1;
+
+	return rstc;
+}
+
+static void __reset_control_put(struct reset_control *rstc)
+{
+	lockdep_assert_held(&reset_list_mutex);
+
+	if (--rstc->refcnt)
+		return;
+
+	module_put(rstc->rcdev->owner);
+
+	list_del(&rstc->list);
+	kfree(rstc);
+}
+
 struct reset_control *__of_reset_control_get(struct device_node *node,
 					     const char *id, int index)
 {
@@ -163,7 +211,7 @@ struct reset_control *__of_reset_control_get(struct device_node *node,
 	if (ret)
 		return ERR_PTR(ret);
 
-	mutex_lock(&reset_controller_list_mutex);
+	mutex_lock(&reset_list_mutex);
 	rcdev = NULL;
 	list_for_each_entry(r, &reset_controller_list, list) {
 		if (args.np == r->of_node) {
@@ -174,27 +222,20 @@ struct reset_control *__of_reset_control_get(struct device_node *node,
 	of_node_put(args.np);
 
 	if (!rcdev) {
-		mutex_unlock(&reset_controller_list_mutex);
+		mutex_unlock(&reset_list_mutex);
 		return ERR_PTR(-EPROBE_DEFER);
 	}
 
 	rstc_id = rcdev->of_xlate(rcdev, &args);
 	if (rstc_id < 0) {
-		mutex_unlock(&reset_controller_list_mutex);
+		mutex_unlock(&reset_list_mutex);
 		return ERR_PTR(rstc_id);
 	}
 
-	try_module_get(rcdev->owner);
-	mutex_unlock(&reset_controller_list_mutex);
-
-	rstc = kzalloc(sizeof(*rstc), GFP_KERNEL);
-	if (!rstc) {
-		module_put(rcdev->owner);
-		return ERR_PTR(-ENOMEM);
-	}
+	/* reset_list_mutex also protects the rcdev's reset_control list */
+	rstc = __reset_control_get(rcdev, rstc_id);
 
-	rstc->rcdev = rcdev;
-	rstc->id = rstc_id;
+	mutex_unlock(&reset_list_mutex);
 
 	return rstc;
 }
@@ -210,8 +251,9 @@ void reset_control_put(struct reset_control *rstc)
 	if (IS_ERR(rstc))
 		return;
 
-	module_put(rstc->rcdev->owner);
-	kfree(rstc);
+	mutex_lock(&reset_list_mutex);
+	__reset_control_put(rstc);
+	mutex_unlock(&reset_list_mutex);
 }
 EXPORT_SYMBOL_GPL(reset_control_put);
 
diff --git a/include/linux/reset-controller.h b/include/linux/reset-controller.h
index ce6b962..2decc20 100644
--- a/include/linux/reset-controller.h
+++ b/include/linux/reset-controller.h
@@ -31,6 +31,7 @@ struct of_phandle_args;
  * @ops: a pointer to device specific struct reset_control_ops
  * @owner: kernel module of the reset controller driver
  * @list: internal list of reset controller devices
+ * @reset_control_head: head of internal list of requested reset controls
  * @of_node: corresponding device tree node as phandle target
  * @of_reset_n_cells: number of cells in reset line specifiers
  * @of_xlate: translation function to translate from specifier as found in the
@@ -41,6 +42,7 @@ struct reset_controller_dev {
 	struct reset_control_ops *ops;
 	struct module *owner;
 	struct list_head list;
+	struct list_head reset_control_head;
 	struct device_node *of_node;
 	int of_reset_n_cells;
 	int (*of_xlate)(struct reset_controller_dev *rcdev,
-- 
2.7.1

[PATCH v4 3/3] reset: Add support for shared reset controls

[Hans de Goede]

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>
---
 drivers/reset/core.c  | 59 +++++++++++++++++++++++++------
 include/linux/reset.h | 96 +++++++++++++++++++++++++++++++++++++++++++--------
 2 files changed, 129 insertions(+), 26 deletions(-)

diff --git a/drivers/reset/core.c b/drivers/reset/core.c
index e439ae2..400e42f 100644
--- a/drivers/reset/core.c
+++ b/drivers/reset/core.c
@@ -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 +99,14 @@ 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 (WARN_ON(rstc->shared))
+		return -EINVAL;
+
 	if (rstc->rcdev->ops->reset)
 		return rstc->rcdev->ops->reset(rstc->rcdev, rstc->id);
 
@@ -107,26 +117,48 @@ 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.
+ *
+ * For shared reset controls a driver cannot expect the hw's registers and
+ * internal state to be reset, but must be prepared for this to happen. 
  */
 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 (WARN_ON(atomic_read(&rstc->deassert_count) == 0))
+			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 +179,7 @@ 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 +187,9 @@ static struct reset_control *__reset_control_get(
 
 	list_for_each_entry(rstc, &rcdev->reset_control_head, list) {
 		if (rstc->id == index) {
+			if (WARN_ON(!rstc->shared || !shared))
+				return ERR_PTR(-EBUSY);
+
 			rstc->refcnt++;
 			return rstc;
 		}
@@ -170,6 +205,7 @@ 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 +224,7 @@ 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 +269,7 @@ 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 +299,7 @@ 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 +308,8 @@ 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);
diff --git a/include/linux/reset.h b/include/linux/reset.h
index 1bb69a2..a552134 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
-- 
2.7.1

[PATCH v4 0/3] reset: Add support for shared reset controls

[Philipp Zabel]

Hi Hans,

Am Dienstag, den 23.02.2016, 18:46 +0100 schrieb Hans de Goede:
> Hi All,
> 
> Here is v4 of my shared reset-controls patch.
> 
> Changes in v3:
> -Rewrite as result of mailinglist discussions changing the API

Thank you, I have applied them with a small fixup on
  git://git.pengutronix.de/git/pza/linux.git reset/next

best regards
Philipp