[PATCH v2 1/3] reset: Add shared reset_control_[de]assert variants

[Hans de Goede <hdegoede-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>]

Add reset_control_deassert_shared / reset_control_assert_shared
functions which are intended for use by drivers for hw blocks which
(may) share a reset line with another driver / hw block.

Unlike the regular reset_control_[de]assert functions these functions
keep track of how often deassert_shared / assert_shared have been called
and keep the line deasserted as long as deassert has been called more
times than assert.

Signed-off-by: Hans de Goede <hdegoede-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
---
Changes in v2:
-This is a new patch in v2 of this patch-set
---
 drivers/reset/core.c             | 121 ++++++++++++++++++++++++++++++++++++---
 include/linux/reset-controller.h |   2 +
 include/linux/reset.h            |   2 +
 3 files changed, 116 insertions(+), 9 deletions(-)

diff --git a/drivers/reset/core.c b/drivers/reset/core.c
index 9ab9290..8c3436c 100644
--- a/drivers/reset/core.c
+++ b/drivers/reset/core.c
@@ -22,16 +22,29 @@ static DEFINE_MUTEX(reset_controller_list_mutex);
 static LIST_HEAD(reset_controller_list);
 
 /**
+ * struct reset_line - a reset line
+ * @list:         list entry for the reset controllers reset line list
+ * @id:           ID of the reset line in the reset controller device
+ * @refcnt:       Number of reset_control structs referencing this device
+ * @deassert_cnt: Number of times this reset line has been deasserted
+ */
+struct reset_line {
+	struct list_head list;
+	unsigned int id;
+	unsigned int refcnt;
+	unsigned int deassert_cnt;
+};
+
+/**
  * struct reset_control - a reset control
  * @rcdev: a pointer to the reset controller device
  *         this reset control belongs to
- * @id: ID of the reset controller in the reset
- *      controller device
+ * @line:  reset line for this reset control
  */
 struct reset_control {
 	struct reset_controller_dev *rcdev;
+	struct reset_line *line;
 	struct device *dev;
-	unsigned int id;
 };
 
 /**
@@ -66,6 +79,8 @@ int reset_controller_register(struct reset_controller_dev *rcdev)
 		rcdev->of_xlate = of_reset_simple_xlate;
 	}
 
+	INIT_LIST_HEAD(&rcdev->reset_line_head);
+
 	mutex_lock(&reset_controller_list_mutex);
 	list_add(&rcdev->list, &reset_controller_list);
 	mutex_unlock(&reset_controller_list_mutex);
@@ -93,7 +108,7 @@ EXPORT_SYMBOL_GPL(reset_controller_unregister);
 int reset_control_reset(struct reset_control *rstc)
 {
 	if (rstc->rcdev->ops->reset)
-		return rstc->rcdev->ops->reset(rstc->rcdev, rstc->id);
+		return rstc->rcdev->ops->reset(rstc->rcdev, rstc->line->id);
 
 	return -ENOTSUPP;
 }
@@ -106,7 +121,7 @@ EXPORT_SYMBOL_GPL(reset_control_reset);
 int reset_control_assert(struct reset_control *rstc)
 {
 	if (rstc->rcdev->ops->assert)
-		return rstc->rcdev->ops->assert(rstc->rcdev, rstc->id);
+		return rstc->rcdev->ops->assert(rstc->rcdev, rstc->line->id);
 
 	return -ENOTSUPP;
 }
@@ -119,13 +134,55 @@ EXPORT_SYMBOL_GPL(reset_control_assert);
 int reset_control_deassert(struct reset_control *rstc)
 {
 	if (rstc->rcdev->ops->deassert)
-		return rstc->rcdev->ops->deassert(rstc->rcdev, rstc->id);
+		return rstc->rcdev->ops->deassert(rstc->rcdev, rstc->line->id);
 
 	return -ENOTSUPP;
 }
 EXPORT_SYMBOL_GPL(reset_control_deassert);
 
 /**
+ * reset_control_assert_shared - asserts a shared reset line
+ * @rstc: reset controller
+ *
+ * Assert a shared reset line, this functions decreases the deassert count
+ * of the line by one and asserts it if, and only if, the deassert count
+ * reaches 0.
+ */
+int reset_control_assert_shared(struct reset_control *rstc)
+{
+	if (!rstc->rcdev->ops->assert)
+		return -ENOTSUPP;
+
+	rstc->line->deassert_cnt--;
+	if (rstc->line->deassert_cnt)
+		return 0;
+
+	return rstc->rcdev->ops->assert(rstc->rcdev, rstc->line->id);
+}
+EXPORT_SYMBOL_GPL(reset_control_assert_shared);
+
+/**
+ * reset_control_deassert_shared - deasserts a shared reset line
+ * @rstc: reset controller
+ *
+ * Assert a shared reset line, this functions increases the deassert count
+ * of the line by one and deasserts the reset line (if it was not already
+ * deasserted).
+ */
+int reset_control_deassert_shared(struct reset_control *rstc)
+{
+	if (!rstc->rcdev->ops->deassert)
+		return -ENOTSUPP;
+
+	rstc->line->deassert_cnt++;
+	if (rstc->line->deassert_cnt != 1)
+		return 0;
+
+	return rstc->rcdev->ops->deassert(rstc->rcdev, rstc->line->id);
+}
+EXPORT_SYMBOL_GPL(reset_control_deassert_shared);
+
+/**
  * reset_control_status - returns a negative errno if not supported, a
  * positive value if the reset line is asserted, or zero if the reset
  * line is not asserted.
@@ -134,12 +191,47 @@ EXPORT_SYMBOL_GPL(reset_control_deassert);
 int reset_control_status(struct reset_control *rstc)
 {
 	if (rstc->rcdev->ops->status)
-		return rstc->rcdev->ops->status(rstc->rcdev, rstc->id);
+		return rstc->rcdev->ops->status(rstc->rcdev, rstc->line->id);
 
 	return -ENOTSUPP;
 }
 EXPORT_SYMBOL_GPL(reset_control_status);
 
+static struct reset_line *reset_line_get(struct reset_controller_dev *rcdev,
+					 unsigned int index)
+{
+	struct reset_line *line;
+
+	list_for_each_entry(line, &rcdev->reset_line_head, list) {
+		if (line->id == index) {
+			line->refcnt++;
+			return line;
+		}
+	}
+
+	line = kzalloc(sizeof(*line), GFP_KERNEL);
+	if (!line)
+		return NULL;
+
+	list_add(&line->list, &rcdev->reset_line_head);
+	line->id = index;
+	line->refcnt = 1;
+
+	return line;
+}
+
+static void reset_line_put(struct reset_line *line)
+{
+	if (!line)
+		return;
+
+	if (--line->refcnt)
+		return;
+
+	list_del(&line->list);
+	kfree(line);
+}
+
 /**
  * of_reset_control_get_by_index - Lookup and obtain a reference to a reset
  * controller by index.
@@ -155,6 +247,7 @@ struct reset_control *of_reset_control_get_by_index(struct device_node *node,
 {
 	struct reset_control *rstc = ERR_PTR(-EPROBE_DEFER);
 	struct reset_controller_dev *r, *rcdev;
+	struct reset_line *line;
 	struct of_phandle_args args;
 	int rstc_id;
 	int ret;
@@ -186,16 +279,22 @@ struct reset_control *of_reset_control_get_by_index(struct device_node *node,
 	}
 
 	try_module_get(rcdev->owner);
+
+	/* reset_controller_list_mutex also protects the reset_line list */
+	line = reset_line_get(rcdev, rstc_id);
+
 	mutex_unlock(&reset_controller_list_mutex);
 
 	rstc = kzalloc(sizeof(*rstc), GFP_KERNEL);
-	if (!rstc) {
+	if (!line || !rstc) {
+		kfree(rstc);
+		reset_line_put(line);
 		module_put(rcdev->owner);
 		return ERR_PTR(-ENOMEM);
 	}
 
 	rstc->rcdev = rcdev;
-	rstc->id = rstc_id;
+	rstc->line = line;
 
 	return rstc;
 }
@@ -259,6 +358,10 @@ void reset_control_put(struct reset_control *rstc)
 	if (IS_ERR(rstc))
 		return;
 
+	mutex_lock(&reset_controller_list_mutex);
+	reset_line_put(rstc->line);
+	mutex_unlock(&reset_controller_list_mutex);
+
 	module_put(rstc->rcdev->owner);
 	kfree(rstc);
 }
diff --git a/include/linux/reset-controller.h b/include/linux/reset-controller.h
index ce6b962..7f2cbd1 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_line_head: head of internal list of reset lines
  * @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_line_head;
 	struct device_node *of_node;
 	int of_reset_n_cells;
 	int (*of_xlate)(struct reset_controller_dev *rcdev,
diff --git a/include/linux/reset.h b/include/linux/reset.h
index c4c097d..1cca8ce 100644
--- a/include/linux/reset.h
+++ b/include/linux/reset.h
@@ -11,6 +11,8 @@ 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_assert_shared(struct reset_control *rstc);
+int reset_control_deassert_shared(struct reset_control *rstc);
 
 struct reset_control *reset_control_get(struct device *dev, const char *id);
 void reset_control_put(struct reset_control *rstc);
-- 
2.5.0