2 files changed, 200 insertions, 32 deletions

diff --git a/drivers/reset/core.c b/drivers/reset/core.c
index 9582efb70025..1e8a42b16f23 100644
--- a/drivers/reset/core.c
+++ b/drivers/reset/core.c
@@ -34,6 +34,7 @@ static LIST_HEAD(reset_lookup_list);
  * @id: ID of the reset controller in the reset
  *      controller device
  * @refcnt: Number of gets of this reset_control
+ * @acquired: Only one reset_control may be acquired for a given rcdev and id.
  * @shared: Is this a shared (1), or an exclusive (0) reset_control?
  * @deassert_cnt: Number of times this reset line has been deasserted
  * @triggered_count: Number of times this reset line has been reset. Currently
@@ -45,6 +46,7 @@ struct reset_control {
         struct list_head list;
         unsigned int id;
         struct kref refcnt;
+        bool acquired;
         bool shared;
         bool array;
         atomic_t deassert_count;
@@ -63,6 +65,17 @@ struct reset_control_array {
         struct reset_control *rstc[];
 };
 
+static const char *rcdev_name(struct reset_controller_dev *rcdev)
+{
+        if (rcdev->dev)
+                return dev_name(rcdev->dev);
+
+        if (rcdev->of_node)
+                return rcdev->of_node->full_name;
+
+        return NULL;
+}
+
 /**
  * of_reset_simple_xlate - translate reset_spec to the reset line number
  * @rcdev: a pointer to the reset controller device
@@ -272,6 +285,9 @@ int reset_control_reset(struct reset_control *rstc)
 
                 if (atomic_inc_return(&rstc->triggered_count) != 1)
                         return 0;
+        } else {
+                if (!rstc->acquired)
+                        return -EPERM;
         }
 
         ret = rstc->rcdev->ops->reset(rstc->rcdev, rstc->id);
@@ -334,6 +350,12 @@ int reset_control_assert(struct reset_control *rstc)
                  */
                 if (!rstc->rcdev->ops->assert)
                         return -ENOTSUPP;
+
+                if (!rstc->acquired) {
+                        WARN(1, "reset %s (ID: %u) is not acquired\n",
+                             rcdev_name(rstc->rcdev), rstc->id);
+                        return -EPERM;
+                }
         }
 
         return rstc->rcdev->ops->assert(rstc->rcdev, rstc->id);
@@ -369,6 +391,12 @@ int reset_control_deassert(struct reset_control *rstc)
 
                 if (atomic_inc_return(&rstc->deassert_count) != 1)
                         return 0;
+        } else {
+                if (!rstc->acquired) {
+                        WARN(1, "reset %s (ID: %u) is not acquired\n",
+                             rcdev_name(rstc->rcdev), rstc->id);
+                        return -EPERM;
+                }
         }
 
         /*
@@ -406,9 +434,81 @@ int reset_control_status(struct reset_control *rstc)
 }
 EXPORT_SYMBOL_GPL(reset_control_status);
 
+/**
+ * reset_control_acquire() - acquires a reset control for exclusive use
+ * @rstc: reset control
+ *
+ * This is used to explicitly acquire a reset control for exclusive use. Note
+ * that exclusive resets are requested as acquired by default. In order for a
+ * second consumer to be able to control the reset, the first consumer has to
+ * release it first. Typically the easiest way to achieve this is to call the
+ * reset_control_get_exclusive_released() to obtain an instance of the reset
+ * control. Such reset controls are not acquired by default.
+ *
+ * Consumers implementing shared access to an exclusive reset need to follow
+ * a specific protocol in order to work together. Before consumers can change
+ * a reset they must acquire exclusive access using reset_control_acquire().
+ * After they are done operating the reset, they must release exclusive access
+ * with a call to reset_control_release(). Consumers are not granted exclusive
+ * access to the reset as long as another consumer hasn't released a reset.
+ *
+ * See also: reset_control_release()
+ */
+int reset_control_acquire(struct reset_control *rstc)
+{
+        struct reset_control *rc;
+
+        if (!rstc)
+                return 0;
+
+        if (WARN_ON(IS_ERR(rstc)))
+                return -EINVAL;
+
+        mutex_lock(&reset_list_mutex);
+
+        if (rstc->acquired) {
+                mutex_unlock(&reset_list_mutex);
+                return 0;
+        }
+
+        list_for_each_entry(rc, &rstc->rcdev->reset_control_head, list) {
+                if (rstc != rc && rstc->id == rc->id) {
+                        if (rc->acquired) {
+                                mutex_unlock(&reset_list_mutex);
+                                return -EBUSY;
+                        }
+                }
+        }
+
+        rstc->acquired = true;
+
+        mutex_unlock(&reset_list_mutex);
+        return 0;
+}
+EXPORT_SYMBOL_GPL(reset_control_acquire);
+
+/**
+ * reset_control_release() - releases exclusive access to a reset control
+ * @rstc: reset control
+ *
+ * Releases exclusive access right to a reset control previously obtained by a
+ * call to reset_control_acquire(). Until a consumer calls this function, no
+ * other consumers will be granted exclusive access.
+ *
+ * See also: reset_control_acquire()
+ */
+void reset_control_release(struct reset_control *rstc)
+{
+        if (!rstc || WARN_ON(IS_ERR(rstc)))
+                return;
+
+        rstc->acquired = false;
+}
+EXPORT_SYMBOL_GPL(reset_control_release);
+
 static struct reset_control *__reset_control_get_internal(
                                 struct reset_controller_dev *rcdev,
-                                unsigned int index, bool shared)
+                                unsigned int index, bool shared, bool acquired)
 {
         struct reset_control *rstc;
 
@@ -416,6 +516,14 @@ static struct reset_control *__reset_control_get_internal(
 
         list_for_each_entry(rstc, &rcdev->reset_control_head, list) {
                 if (rstc->id == index) {
+                        /*
+                         * Allow creating a secondary exclusive reset_control
+                         * that is initially not acquired for an already
+                         * controlled reset line.
+                         */
+                        if (!rstc->shared && !shared && !acquired)
+                                break;
+
                         if (WARN_ON(!rstc->shared || !shared))
                                 return ERR_PTR(-EBUSY);
 
@@ -434,6 +542,7 @@ static struct reset_control *__reset_control_get_internal(
         list_add(&rstc->list, &rcdev->reset_control_head);
         rstc->id = index;
         kref_init(&rstc->refcnt);
+        rstc->acquired = acquired;
         rstc->shared = shared;
 
         return rstc;
@@ -461,7 +570,7 @@ static void __reset_control_put_internal(struct reset_control *rstc)
 
 struct reset_control *__of_reset_control_get(struct device_node *node,
                                      const char *id, int index, bool shared,
-                                     bool optional)
+                                     bool optional, bool acquired)
 {
         struct reset_control *rstc;
         struct reset_controller_dev *r, *rcdev;
@@ -514,7 +623,7 @@ 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_internal(rcdev, rstc_id, shared);
+        rstc = __reset_control_get_internal(rcdev, rstc_id, shared, acquired);
 
 out:
         mutex_unlock(&reset_list_mutex);
@@ -544,7 +653,7 @@ __reset_controller_by_name(const char *name)
 
 static struct reset_control *
 __reset_control_get_from_lookup(struct device *dev, const char *con_id,
-                                bool shared, bool optional)
+                                bool shared, bool optional, bool acquired)
 {
         const struct reset_control_lookup *lookup;
         struct reset_controller_dev *rcdev;
@@ -574,7 +683,7 @@ __reset_control_get_from_lookup(struct device *dev, const char *con_id,
 
                         rstc = __reset_control_get_internal(rcdev,
                                                             lookup->index,
-                                                            shared);
+                                                            shared, acquired);
                         mutex_unlock(&reset_list_mutex);
                         break;
                 }
@@ -589,13 +698,18 @@ __reset_control_get_from_lookup(struct device *dev, const char *con_id,
 }
 
 struct reset_control *__reset_control_get(struct device *dev, const char *id,
-                                          int index, bool shared, bool optional)
+                                          int index, bool shared, bool optional,
+                                          bool acquired)
 {
+        if (WARN_ON(shared && acquired))
+                return ERR_PTR(-EINVAL);
+
         if (dev->of_node)
                 return __of_reset_control_get(dev->of_node, id, index, shared,
-                                              optional);
+                                              optional, acquired);
 
-        return __reset_control_get_from_lookup(dev, id, shared, optional);
+        return __reset_control_get_from_lookup(dev, id, shared, optional,
+                                               acquired);
 }
 EXPORT_SYMBOL_GPL(__reset_control_get);
 
@@ -636,7 +750,7 @@ 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, bool shared,
-                                     bool optional)
+                                     bool optional, bool acquired)
 {
         struct reset_control **ptr, *rstc;
 
@@ -645,7 +759,7 @@ struct reset_control *__devm_reset_control_get(struct device *dev,
         if (!ptr)
                 return ERR_PTR(-ENOMEM);
 
-        rstc = __reset_control_get(dev, id, index, shared, optional);
+        rstc = __reset_control_get(dev, id, index, shared, optional, acquired);
         if (!IS_ERR(rstc)) {
                 *ptr = rstc;
                 devres_add(dev, ptr);
@@ -672,7 +786,7 @@ int __device_reset(struct device *dev, bool optional)
         struct reset_control *rstc;
         int ret;
 
-        rstc = __reset_control_get(dev, NULL, 0, 0, optional);
+        rstc = __reset_control_get(dev, NULL, 0, 0, optional, true);
         if (IS_ERR(rstc))
                 return PTR_ERR(rstc);
 
@@ -736,7 +850,8 @@ of_reset_control_array_get(struct device_node *np, bool shared, bool optional)
                 return ERR_PTR(-ENOMEM);
 
         for (i = 0; i < num; i++) {
-                rstc = __of_reset_control_get(np, NULL, i, shared, optional);
+                rstc = __of_reset_control_get(np, NULL, i, shared, optional,
+                                              true);
                 if (IS_ERR(rstc))
                         goto err_rst;
                 resets->rstc[i] = rstc;
diff --git a/include/linux/reset.h b/include/linux/reset.h
index c1901b61ca30..ea9a8a1ce4b1 100644
--- a/include/linux/reset.h
+++ b/include/linux/reset.h
@@ -14,18 +14,20 @@ int reset_control_reset(struct reset_control *rstc);
 int reset_control_assert(struct reset_control *rstc);
 int reset_control_deassert(struct reset_control *rstc);
 int reset_control_status(struct reset_control *rstc);
+int reset_control_acquire(struct reset_control *rstc);
+void reset_control_release(struct reset_control *rstc);
 
 struct reset_control *__of_reset_control_get(struct device_node *node,
                                      const char *id, int index, bool shared,
-                                     bool optional);
+                                     bool optional, bool acquired);
 struct reset_control *__reset_control_get(struct device *dev, const char *id,
                                           int index, bool shared,
-                                          bool optional);
+                                          bool optional, bool acquired);
 void reset_control_put(struct reset_control *rstc);
 int __device_reset(struct device *dev, bool optional);
 struct reset_control *__devm_reset_control_get(struct device *dev,
                                      const char *id, int index, bool shared,
-                                     bool optional);
+                                     bool optional, bool acquired);
 
 struct reset_control *devm_reset_control_array_get(struct device *dev,
                                                    bool shared, bool optional);
@@ -56,6 +58,15 @@ static inline int reset_control_status(struct reset_control *rstc)
         return 0;
 }
 
+static inline int reset_control_acquire(struct reset_control *rstc)
+{
+        return 0;
+}
+
+static inline void reset_control_release(struct reset_control *rstc)
+{
+}
+
 static inline void reset_control_put(struct reset_control *rstc)
 {
 }
@@ -68,21 +79,23 @@ static inline int __device_reset(struct device *dev, bool optional)
 static inline struct reset_control *__of_reset_control_get(
                                         struct device_node *node,
                                         const char *id, int index, bool shared,
-                                        bool optional)
+                                        bool optional, bool acquired)
 {
         return optional ? NULL : ERR_PTR(-ENOTSUPP);
 }
 
 static inline struct reset_control *__reset_control_get(
                                         struct device *dev, const char *id,
-                                        int index, bool shared, bool optional)
+                                        int index, bool shared, bool optional,
+                                        bool acquired)
 {
         return optional ? NULL : ERR_PTR(-ENOTSUPP);
 }
 
 static inline struct reset_control *__devm_reset_control_get(
                                         struct device *dev, const char *id,
-                                        int index, bool shared, bool optional)
+                                        int index, bool shared, bool optional,
+                                        bool acquired)
 {
         return optional ? NULL : ERR_PTR(-ENOTSUPP);
 }
@@ -134,7 +147,28 @@ static inline int device_reset_optional(struct device *dev)
 static inline struct reset_control *
 __must_check reset_control_get_exclusive(struct device *dev, const char *id)
 {
-        return __reset_control_get(dev, id, 0, false, false);
+        return __reset_control_get(dev, id, 0, false, false, true);
+}
+
+/**
+ * reset_control_get_exclusive_released - Lookup and obtain a temoprarily
+ *                                        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.
+ * reset-controls returned by this function must be acquired via
+ * reset_control_acquire() before they can be used and should be released
+ * via reset_control_release() afterwards.
+ *
+ * Use of id names is optional.
+ */
+static inline struct reset_control *
+__must_check reset_control_get_exclusive_released(struct device *dev,
+                                                  const char *id)
+{
+        return __reset_control_get(dev, id, 0, false, false, false);
 }
 
 /**
@@ -162,19 +196,19 @@ __must_check reset_control_get_exclusive(struct device *dev, const char *id)
 static inline struct reset_control *reset_control_get_shared(
                                         struct device *dev, const char *id)
 {
-        return __reset_control_get(dev, id, 0, true, false);
+        return __reset_control_get(dev, id, 0, true, false, false);
 }
 
 static inline struct reset_control *reset_control_get_optional_exclusive(
                                         struct device *dev, const char *id)
 {
-        return __reset_control_get(dev, id, 0, false, true);
+        return __reset_control_get(dev, id, 0, false, true, true);
 }
 
 static inline struct reset_control *reset_control_get_optional_shared(
                                         struct device *dev, const char *id)
 {
-        return __reset_control_get(dev, id, 0, true, true);
+        return __reset_control_get(dev, id, 0, true, true, false);
 }
 
 /**
@@ -190,7 +224,7 @@ static inline struct reset_control *reset_control_get_optional_shared(
 static inline struct reset_control *of_reset_control_get_exclusive(
                                 struct device_node *node, const char *id)
 {
-        return __of_reset_control_get(node, id, 0, false, false);
+        return __of_reset_control_get(node, id, 0, false, false, true);
 }
 
 /**
@@ -215,7 +249,7 @@ static inline struct reset_control *of_reset_control_get_exclusive(
 static inline struct reset_control *of_reset_control_get_shared(
                                 struct device_node *node, const char *id)
 {
-        return __of_reset_control_get(node, id, 0, true, false);
+        return __of_reset_control_get(node, id, 0, true, false, false);
 }
 
 /**
@@ -232,7 +266,7 @@ static inline struct reset_control *of_reset_control_get_shared(
 static inline struct reset_control *of_reset_control_get_exclusive_by_index(
                                         struct device_node *node, int index)
 {
-        return __of_reset_control_get(node, NULL, index, false, false);
+        return __of_reset_control_get(node, NULL, index, false, false, true);
 }
 
 /**
@@ -260,7 +294,7 @@ static inline struct reset_control *of_reset_control_get_exclusive_by_index(
 static inline struct reset_control *of_reset_control_get_shared_by_index(
                                         struct device_node *node, int index)
 {
-        return __of_reset_control_get(node, NULL, index, true, false);
+        return __of_reset_control_get(node, NULL, index, true, false, false);
 }
 
 /**
@@ -279,7 +313,26 @@ static inline struct reset_control *
 __must_check devm_reset_control_get_exclusive(struct device *dev,
                                               const char *id)
 {
-        return __devm_reset_control_get(dev, id, 0, false, false);
+        return __devm_reset_control_get(dev, id, 0, false, false, true);
+}
+
+/**
+ * devm_reset_control_get_exclusive_released - resource managed
+ *                                             reset_control_get_exclusive_released()
+ * @dev: device to be reset by the controller
+ * @id: reset line name
+ *
+ * Managed reset_control_get_exclusive_released(). For reset controllers
+ * returned from this function, reset_control_put() is called automatically on
+ * driver detach.
+ *
+ * See reset_control_get_exclusive_released() for more information.
+ */
+static inline struct reset_control *
+__must_check devm_reset_control_get_exclusive_released(struct device *dev,
+                                                       const char *id)
+{
+        return __devm_reset_control_get(dev, id, 0, false, false, false);
 }
 
 /**
@@ -294,19 +347,19 @@ __must_check devm_reset_control_get_exclusive(struct device *dev,
 static inline struct reset_control *devm_reset_control_get_shared(
                                         struct device *dev, const char *id)
 {
-        return __devm_reset_control_get(dev, id, 0, true, false);
+        return __devm_reset_control_get(dev, id, 0, true, false, false);
 }
 
 static inline struct reset_control *devm_reset_control_get_optional_exclusive(
                                         struct device *dev, const char *id)
 {
-        return __devm_reset_control_get(dev, id, 0, false, true);
+        return __devm_reset_control_get(dev, id, 0, false, true, true);
 }
 
 static inline struct reset_control *devm_reset_control_get_optional_shared(
                                         struct device *dev, const char *id)
 {
-        return __devm_reset_control_get(dev, id, 0, true, true);
+        return __devm_reset_control_get(dev, id, 0, true, true, false);
 }
 
 /**
@@ -324,7 +377,7 @@ static inline struct reset_control *devm_reset_control_get_optional_shared(
 static inline struct reset_control *
 devm_reset_control_get_exclusive_by_index(struct device *dev, int index)
 {
-        return __devm_reset_control_get(dev, NULL, index, false, false);
+        return __devm_reset_control_get(dev, NULL, index, false, false, true);
 }
 
 /**
@@ -340,7 +393,7 @@ devm_reset_control_get_exclusive_by_index(struct device *dev, int index)
 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, true, false);
+        return __devm_reset_control_get(dev, NULL, index, true, false, false);
 }
 
 /*