[RFC PATCHv2 3/3] hwspinlock/core: add support for reserved locks

[Suman Anna]

The HwSpinlock core allows requesting either a specific lock or an
available normal lock. The specific locks are usually reserved during
board init time, while the normal available locks are intended to be
assigned at runtime for clients that do not care about a specific
lock.

The HwSpinlock core has been enhanced to:
  1. mark certain locks as 'reserved' by parsing the DT blob for any
     locks used by client nodes.
  2. restrict the anonymous hwspin_lock_request() API to allocate only
     from non-reserved locks for DT boots.
  3. limit these reserved locks to be allocated only using the
     hwspin_lock_request_specific() API for DT boots.

Signed-off-by: Suman Anna <s-anna@xxxxxx>
---
 drivers/hwspinlock/hwspinlock_core.c | 61 ++++++++++++++++++++++++++++++++++--
 1 file changed, 59 insertions(+), 2 deletions(-)

diff --git a/drivers/hwspinlock/hwspinlock_core.c b/drivers/hwspinlock/hwspinlock_core.c
index f0d8475..d49a077 100644
--- a/drivers/hwspinlock/hwspinlock_core.c
+++ b/drivers/hwspinlock/hwspinlock_core.c
@@ -474,6 +474,53 @@ static int hwspinlock_device_add(struct hwspinlock_device *bank)
 }
 
 /**
+ * hwspin_mark_reserved_locks() - mark reserved locks
+ *
+ * This is an internal function that mark all the reserved locks within
+ * a hwspinlock device during the registration phase, and is applicable
+ * only for device-tree boots. The locks are marked by browsing through
+ * all the user nodes with the property "hwlocks", so that a separate
+ * property is not needed in the hwspinlock device itself. Note that it
+ * also marks locks used on disabled user nodes.
+ */
+static void hwspin_mark_reserved_locks(struct hwspinlock_device *bank)
+{
+	struct device_node *np = bank->dev->of_node;
+	const char *prop_name = "hwlocks";
+	const char *cells_name = "#hwlock-cells";
+	struct device_node *node = NULL;
+	struct of_phandle_args args;
+	struct hwspinlock *hwlock;
+	int i, id, count, ret;
+
+	for_each_node_with_property(node, prop_name) {
+		count = of_count_phandle_with_args(node, prop_name, cells_name);
+		if (count <= 0)
+			continue;
+
+		for (i = 0; i < count; i++, of_node_put(args.np)) {
+			args.np = NULL;
+			ret = of_parse_phandle_with_args(node, prop_name,
+							 cells_name, i, &args);
+			if (ret || np != args.np)
+				continue;
+
+			id = of_hwspin_lock_simple_xlate(bank, &args);
+			if (id < 0 || id >= bank->num_locks)
+				continue;
+
+			hwlock = &bank->lock[id];
+			if (hwlock->type == HWSPINLOCK_RESERVED) {
+				dev_err(bank->dev, "potential reuse of hwspinlock %d between multiple clients on %s\n",
+					id, np->full_name);
+				continue;
+			}
+			hwlock->type = HWSPINLOCK_RESERVED;
+		}
+	}
+}
+
+/**
  * hwspin_lock_register() - register a new hw spinlock device
  * @bank: the hwspinlock device, which usually provides numerous hw locks
  * @dev: the backing device
@@ -511,12 +558,16 @@ int hwspin_lock_register(struct hwspinlock_device *bank, struct device *dev,
 	if (ret)
 		return ret;
 
+	if (dev->of_node)
+		hwspin_mark_reserved_locks(bank);
+
 	for (i = 0; i < num_locks; i++) {
 		hwlock = &bank->lock[i];
 
 		spin_lock_init(&hwlock->lock);
 		hwlock->bank = bank;
-		hwlock->type = HWSPINLOCK_UNUSED;
+		if (hwlock->type != HWSPINLOCK_RESERVED)
+			hwlock->type = HWSPINLOCK_UNUSED;
 
 		ret = hwspin_lock_register_single(hwlock, base_id + i);
 		if (ret)
@@ -699,7 +750,13 @@ struct hwspinlock *hwspin_lock_request_specific(unsigned int id)
 	/* sanity check (this shouldn't happen) */
 	WARN_ON(hwlock_to_id(hwlock) != id);
 
-	/* make sure this hwspinlock is unused */
+	if (hwlock->bank->dev->of_node && hwlock->type != HWSPINLOCK_RESERVED) {
+		pr_warn("hwspinlock %u is not a reserved lock\n", id);
+		hwlock = NULL;
+		goto out;
+	}
+
+	/* make sure this hwspinlock is an unused reserved lock */
 	ret = radix_tree_tag_get(&hwspinlock_tree, id, hwlock->type);
 	if (ret == 0) {
 		pr_warn("hwspinlock %u is already in use\n", id);
-- 
2.0.4

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