Merge branch 'reset/acquire' of git://git.pengutronix.de/git/pza/linux into drm/tegra/for-next

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
@@ -232,6 +245,34 @@ static int reset_control_array_deassert(struct reset_control_array *resets)
 	return ret;
 }
 
+static int reset_control_array_acquire(struct reset_control_array *resets)
+{
+	unsigned int i;
+	int err;
+
+	for (i = 0; i < resets->num_rstcs; i++) {
+		err = reset_control_acquire(resets->rstc[i]);
+		if (err < 0)
+			goto release;
+	}
+
+	return 0;
+
+release:
+	while (i--)
+		reset_control_release(resets->rstc[i]);
+
+	return err;
+}
+
+static void reset_control_array_release(struct reset_control_array *resets)
+{
+	unsigned int i;
+
+	for (i = 0; i < resets->num_rstcs; i++)
+		reset_control_release(resets->rstc[i]);
+}
+
 static inline bool reset_control_is_array(struct reset_control *rstc)
 {
 	return rstc->array;
@@ -272,6 +313,9 @@ 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 +378,12 @@ 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 +419,12 @@ 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 +462,87 @@ 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;
+
+	if (reset_control_is_array(rstc))
+		return reset_control_array_acquire(rstc_to_array(rstc));
+
+	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;
+
+	if (reset_control_is_array(rstc))
+		reset_control_array_release(rstc_to_array(rstc));
+	else
+		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 +550,14 @@ 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 +576,7 @@ 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 +604,7 @@ 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 +657,7 @@ 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 +687,7 @@ __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 +717,7 @@ __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 +732,18 @@ __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 +784,7 @@ 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 +793,7 @@ 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 +820,7 @@ 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);
 
@@ -716,12 +864,15 @@ static int of_reset_control_get_count(struct device_node *node)
  * @np: device node for the device that requests the reset controls array
  * @shared: whether reset controls are shared or not
  * @optional: whether it is optional to get the reset controls
+ * @acquired: only one reset control may be acquired for a given controller
+ *            and ID
  *
  * Returns pointer to allocated reset_control_array on success or
  * error on failure
  */
 struct reset_control *
-of_reset_control_array_get(struct device_node *np, bool shared, bool optional)
+of_reset_control_array_get(struct device_node *np, bool shared, bool optional,
+			   bool acquired)
 {
 	struct reset_control_array *resets;
 	struct reset_control *rstc;
@@ -736,7 +887,8 @@ 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,
+					      acquired);
 		if (IS_ERR(rstc))
 			goto err_rst;
 		resets->rstc[i] = rstc;
@@ -783,7 +935,7 @@ devm_reset_control_array_get(struct device *dev, bool shared, bool optional)
 	if (!devres)
 		return ERR_PTR(-ENOMEM);
 
-	rstc = of_reset_control_array_get(dev->of_node, shared, optional);
+	rstc = of_reset_control_array_get(dev->of_node, shared, optional, true);
 	if (IS_ERR(rstc)) {
 		devres_free(devres);
 		return rstc;

drivers/usb/dwc3/dwc3-of-simple.c

@@ -107,7 +107,8 @@ static int dwc3_of_simple_probe(struct platform_device *pdev)
 		simple->pulse_resets = true;
 	}
 
-	simple->resets = of_reset_control_array_get(np, shared_resets, true);
+	simple->resets = of_reset_control_array_get(np, shared_resets, true,
+						    true);
 	if (IS_ERR(simple->resets)) {
 		ret = PTR_ERR(simple->resets);
 		dev_err(dev, "failed to get device resets, err=%d\n", ret);

include/linux/reset.h

@@ -14,23 +14,26 @@ 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);
 struct reset_control *of_reset_control_array_get(struct device_node *np,
-						 bool shared, bool optional);
+						 bool shared, bool optional,
+						 bool acquired);
 
 int reset_control_get_count(struct device *dev);
 
@@ -56,6 +59,15 @@ 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 +80,23 @@ 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);
 }
@@ -94,7 +108,8 @@ devm_reset_control_array_get(struct device *dev, bool shared, bool optional)
 }
 
 static inline struct reset_control *
-of_reset_control_array_get(struct device_node *np, bool shared, bool optional)
+of_reset_control_array_get(struct device_node *np, bool shared, bool optional,
+			   bool acquired)
 {
 	return optional ? NULL : ERR_PTR(-ENOTSUPP);
 }
@@ -134,7 +149,28 @@ 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 +198,19 @@ __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 +226,7 @@ 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 +251,7 @@ 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 +268,7 @@ 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 +296,7 @@ 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 +315,26 @@ 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 +349,19 @@ __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 +379,7 @@ 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 +395,7 @@ 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);
 }
 
 /*
@@ -412,24 +467,30 @@ devm_reset_control_array_get_optional_shared(struct device *dev)
 static inline struct reset_control *
 of_reset_control_array_get_exclusive(struct device_node *node)
 {
-	return of_reset_control_array_get(node, false, false);
+	return of_reset_control_array_get(node, false, false, true);
+}
+
+static inline struct reset_control *
+of_reset_control_array_get_exclusive_released(struct device_node *node)
+{
+	return of_reset_control_array_get(node, false, false, false);
 }
 
 static inline struct reset_control *
 of_reset_control_array_get_shared(struct device_node *node)
 {
-	return of_reset_control_array_get(node, true, false);
+	return of_reset_control_array_get(node, true, false, true);
 }
 
 static inline struct reset_control *
 of_reset_control_array_get_optional_exclusive(struct device_node *node)
 {
-	return of_reset_control_array_get(node, false, true);
+	return of_reset_control_array_get(node, false, true, true);
 }
 
 static inline struct reset_control *
 of_reset_control_array_get_optional_shared(struct device_node *node)
 {
-	return of_reset_control_array_get(node, true, true);
+	return of_reset_control_array_get(node, true, true, true);
 }
 #endif