[PATCH v8 2/4] hwspinlock/core: add device tree support

[Suman Anna <s-anna@ti.com>]

This patch adds a new OF-friendly API of_hwspin_lock_get_id()
for hwspinlock clients to use/request locks from a hwspinlock
device instantiated through a device-tree blob. This new API
can be used by hwspinlock clients to get the id for a specific
lock using the phandle + args specifier, so that it can be
requested using the available hwspin_lock_request_specific()
API.

Signed-off-by: Suman Anna <s-anna@ti.com>
---
v8: Removed the previous OF helpers of_hwspin_lock_get_num_locks()
    & of_hwspin_lock_get_base_id() due to the revised generic
    bindings. Added back the support for deferred probing and
    pargs specifier validation like in v6, but without using an
    added list for storing registered hwspinlock devices.

 Documentation/hwspinlock.txt         | 10 +++++
 drivers/hwspinlock/hwspinlock_core.c | 79 ++++++++++++++++++++++++++++++++++++
 include/linux/hwspinlock.h           |  7 ++++
 3 files changed, 96 insertions(+)

diff --git a/Documentation/hwspinlock.txt b/Documentation/hwspinlock.txt
index 62f7d4ea6e26..61c1ee98e59f 100644
--- a/Documentation/hwspinlock.txt
+++ b/Documentation/hwspinlock.txt
@@ -48,6 +48,16 @@ independent, drivers.
      ids for predefined purposes.
      Should be called from a process context (might sleep).
 
+  int of_hwspin_lock_get_id(struct device_node *np, int index);
+   - retrieve the global lock id for an OF phandle-based specific lock.
+     This function provides a means for DT users of a hwspinlock module
+     to get the global lock id of a specific hwspinlock, so that it can
+     be requested using the normal hwspin_lock_request_specific() API.
+     The function returns a lock id number on success, -EPROBE_DEFER if
+     the hwspinlock device is not yet registered with the core, or other
+     error values.
+     Should be called from a process context (might sleep).
+
   int hwspin_lock_free(struct hwspinlock *hwlock);
    - free a previously-assigned hwspinlock; returns 0 on success, or an
      appropriate error code on failure (e.g. -EINVAL if the hwspinlock
diff --git a/drivers/hwspinlock/hwspinlock_core.c b/drivers/hwspinlock/hwspinlock_core.c
index 461a0d739d75..f8539f624e3d 100644
--- a/drivers/hwspinlock/hwspinlock_core.c
+++ b/drivers/hwspinlock/hwspinlock_core.c
@@ -27,6 +27,7 @@
 #include <linux/hwspinlock.h>
 #include <linux/pm_runtime.h>
 #include <linux/mutex.h>
+#include <linux/of.h>
 
 #include "hwspinlock_internal.h"
 
@@ -257,6 +258,84 @@ void __hwspin_unlock(struct hwspinlock *hwlock, int mode, unsigned long *flags)
 }
 EXPORT_SYMBOL_GPL(__hwspin_unlock);
 
+/**
+ * of_hwspin_lock_simple_xlate - translate hwlock_spec to return a lock id
+ * @bank: the hwspinlock device bank
+ * @hwlock_spec: hwlock specifier as found in the device tree
+ *
+ * This is a simple translation function, suitable for hwspinlock platform
+ * drivers that only has a lock specifier length of 1.
+ *
+ * Returns a relative index of the lock within a specified bank on success,
+ * or -EINVAL on invalid specifier cell count.
+ */
+static inline int
+of_hwspin_lock_simple_xlate(const struct of_phandle_args *hwlock_spec)
+{
+	if (WARN_ON(hwlock_spec->args_count != 1))
+		return -EINVAL;
+
+	return hwlock_spec->args[0];
+}
+
+/**
+ * of_hwspin_lock_get_id() - get lock id for an OF phandle-based specific lock
+ * @np: device node from which to request the specific hwlock
+ * @index: index of the hwlock in the list of values
+ *
+ * This function provides a means for DT users of the hwspinlock module to
+ * get the global lock id of a specific hwspinlock using the phandle of the
+ * hwspinlock device, so that it can be requested using the normal
+ * hwspin_lock_request_specific() API.
+ *
+ * Returns the global lock id number on success, -EPROBE_DEFER if the hwspinlock
+ * device is not yet registered, -EINVAL on invalid args specifier value or an
+ * appropriate error as returned from the OF parsing of the DT client node.
+ */
+int of_hwspin_lock_get_id(struct device_node *np, int index)
+{
+	struct of_phandle_args args;
+	struct hwspinlock *hwlock;
+	struct radix_tree_iter iter;
+	void **slot;
+	int id;
+	int ret;
+
+	ret = of_parse_phandle_with_args(np, "hwlocks", "#hwlock-cells", index,
+					 &args);
+	if (ret)
+		return ret;
+
+	/* perform a sanity check of the hwspinlock device */
+	ret = -EPROBE_DEFER;
+	rcu_read_lock();
+	radix_tree_for_each_slot(slot, &hwspinlock_tree, &iter, 0) {
+		hwlock = radix_tree_deref_slot(slot);
+		if (unlikely(!hwlock))
+			continue;
+
+		if (hwlock->bank->dev->of_node == args.np) {
+			ret = 0;
+			break;
+		}
+	}
+	rcu_read_unlock();
+	if (ret < 0)
+		goto out;
+
+	id = of_hwspin_lock_simple_xlate(&args);
+	if (id < 0 || id >= hwlock->bank->num_locks) {
+		ret = -EINVAL;
+		goto out;
+	}
+	id += hwlock->bank->base_id;
+
+out:
+	of_node_put(args.np);
+	return ret ? ret : id;
+}
+EXPORT_SYMBOL_GPL(of_hwspin_lock_get_id);
+
 static int hwspin_lock_register_single(struct hwspinlock *hwlock, int id)
 {
 	struct hwspinlock *tmp;
diff --git a/include/linux/hwspinlock.h b/include/linux/hwspinlock.h
index 3343298e40e8..859d673d98c8 100644
--- a/include/linux/hwspinlock.h
+++ b/include/linux/hwspinlock.h
@@ -26,6 +26,7 @@
 #define HWLOCK_IRQ	0x02	/* Disable interrupts, don't save state */
 
 struct device;
+struct device_node;
 struct hwspinlock;
 struct hwspinlock_device;
 struct hwspinlock_ops;
@@ -66,6 +67,7 @@ int hwspin_lock_unregister(struct hwspinlock_device *bank);
 struct hwspinlock *hwspin_lock_request(void);
 struct hwspinlock *hwspin_lock_request_specific(unsigned int id);
 int hwspin_lock_free(struct hwspinlock *hwlock);
+int of_hwspin_lock_get_id(struct device_node *np, int index);
 int hwspin_lock_get_id(struct hwspinlock *hwlock);
 int __hwspin_lock_timeout(struct hwspinlock *, unsigned int, int,
 							unsigned long *);
@@ -120,6 +122,11 @@ void __hwspin_unlock(struct hwspinlock *hwlock, int mode, unsigned long *flags)
 {
 }
 
+static inline int of_hwspin_lock_get_id(struct device_node *np, int index)
+{
+	return 0;
+}
+
 static inline int hwspin_lock_get_id(struct hwspinlock *hwlock)
 {
 	return 0;
-- 
2.3.0