[PATCHv5 RFC 12/15] hwspinlock/core: add OF helper to parse reserved locks

[Suman Anna]

The property 'hwlock-reserved-locks' will be used to represent
the number of locks to be reserved for clients that would need
to request/operate on specific locks. A new OF helper function,
of_hwspin_lock_get_num_reserved_locks(), is added to minimize
duplication in different platform implementations.

The function will return a value of 0 if the property is not
defined, so as to support a default behavior of marking all
locks as unused and open for anonymous allocations.

Signed-off-by: Suman Anna <s-anna@xxxxxx>
---
 .../devicetree/bindings/hwlock/hwlock.txt          |  3 +++
 drivers/hwspinlock/hwspinlock_core.c               | 25 ++++++++++++++++++++++
 include/linux/hwspinlock.h                         |  1 +
 3 files changed, 29 insertions(+)

diff --git a/Documentation/devicetree/bindings/hwlock/hwlock.txt b/Documentation/devicetree/bindings/hwlock/hwlock.txt
index d538a9b..88d16d2 100644
--- a/Documentation/devicetree/bindings/hwlock/hwlock.txt
+++ b/Documentation/devicetree/bindings/hwlock/hwlock.txt
@@ -18,6 +18,9 @@ Common properties:
 			property is needed on hwlock devices, where the number
 			of supported locks within a hwlock device cannot be
 			read from a register.
+- hwlock-reserved-locks: Number of locks to reserve for clients requiring
+			specific locks. This value cannot exceed the value of
+			hwlock-num-locks.
 - hwlock-base-id:	An unique base Id for the locks for a particular hwlock
 			device. This property is mandatory ONLY if a SoC has
 			several hwlock devices.
diff --git a/drivers/hwspinlock/hwspinlock_core.c b/drivers/hwspinlock/hwspinlock_core.c
index e05cea8..e74b55b 100644
--- a/drivers/hwspinlock/hwspinlock_core.c
+++ b/drivers/hwspinlock/hwspinlock_core.c
@@ -286,6 +286,31 @@ int of_hwspin_lock_get_base_id(struct device_node *dn)
 EXPORT_SYMBOL_GPL(of_hwspin_lock_get_base_id);
 
 /**
+ * of_hwspin_lock_get_num_reserved_locks() - retrieve number of reserved locks
+ * @dn: device node pointer
+ *
+ * This is an OF helper function that can be called by the underlying platform
+ * specific implementations, to retrieve the number of locks to reserve from
+ * the hwspinlock device instance's base id. The hwlock-reserved-locks DT
+ * property needs to be defined for requesting any DT-based locks.
+ *
+ * Returns a positive number of locks on success, a default value of 0 if the
+ * property is missing or an appropriate error code as returned by the OF layer
+ */
+int of_hwspin_lock_get_num_reserved_locks(struct device_node *dn)
+{
+	unsigned int val = 0;
+	int ret;
+
+	ret = of_property_read_u32(dn, "hwlock-reserved-locks", &val);
+	if (!ret || ret == -EINVAL)
+		ret = val;
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(of_hwspin_lock_get_num_reserved_locks);
+
+/**
  * of_hwspin_lock_get_num_locks() - OF helper to retrieve number of locks
  * @dn: device node pointer
  *
diff --git a/include/linux/hwspinlock.h b/include/linux/hwspinlock.h
index d120035..d18431f 100644
--- a/include/linux/hwspinlock.h
+++ b/include/linux/hwspinlock.h
@@ -69,6 +69,7 @@ int of_hwspin_lock_simple_xlate(struct hwspinlock_device *bank,
 				const struct of_phandle_args *hwlock_spec);
 int of_hwspin_lock_get_base_id(struct device_node *dn);
 int of_hwspin_lock_get_num_locks(struct device_node *dn);
+int of_hwspin_lock_get_num_reserved_locks(struct device_node *dn);
 int hwspin_lock_register(struct hwspinlock_device *bank, struct device *dev,
 		const struct hwspinlock_ops *ops, int base_id, int num_locks,
 		int num_reserved_locks);
-- 
1.9.2

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