[PATCHv6 4/5] hwspinlock/core: add common OF helpers

[Suman Anna]

This patch adds three new OF helper functions to use/request
locks from a hwspinlock device instantiated through a
device-tree blob.

1. The of_hwspin_lock_get_num_locks() is a common OF helper
   function to read the 'hwlock-num-locks' property.
2. The of_hwspin_lock_get_base_id() is a common OF helper
   function to read the 'hwlock-base-id' property.
3. The of_hwspin_lock_get_id() 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@xxxxxx>
---
 Documentation/hwspinlock.txt         |  26 ++++++++
 drivers/hwspinlock/hwspinlock_core.c | 122 +++++++++++++++++++++++++++++++++++
 include/linux/hwspinlock.h           |  15 ++++-
 3 files changed, 160 insertions(+), 3 deletions(-)

diff --git a/Documentation/hwspinlock.txt b/Documentation/hwspinlock.txt
index 640ae47..c15dc9f 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 valid 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
@@ -243,6 +253,22 @@ int hwspinlock_example2(void)
      Returns the address of hwspinlock on success, or NULL on error (e.g.
      if the hwspinlock is still in use).
 
+  int of_hwspin_lock_get_num_locks(struct device_node *dn);
+   - is a common OF helper function that can be used by some underlying
+     vendor-specific implementations. This can be used by implementations
+     that require and define the number of locks supported within a hwspinlock
+     bank as a device tree node property. This function should be called by
+     needed implementations before registering a hwspinlock device with the
+     core.
+
+  int of_hwspin_lock_get_base_id(struct device_node *dn);
+   - is a common OF helper function that can be used by some underlying
+     vendor-specific implementations. This can be used by implementations
+     that require and define the base index for a block of locks present
+     within a hwspinlock bank as a device tree node property. This function
+     should be called by needed implementations before registering a hwspinlock
+     device with the core.
+
 5. Important structs
 
 struct hwspinlock_device is a device which usually contains a bank
diff --git a/drivers/hwspinlock/hwspinlock_core.c b/drivers/hwspinlock/hwspinlock_core.c
index 48f7866..7d9f749 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"
 
@@ -262,6 +263,127 @@ 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 negative value on error, and a relative index of the lock within
+ * a specified bank on success.
+ */
+static int of_hwspin_lock_simple_xlate(struct hwspinlock_device *bank,
+				const struct of_phandle_args *hwlock_spec)
+{
+	/* sanity check (these shouldn't happen) */
+	if (WARN_ON(!bank->dev->of_node))
+		return -EINVAL;
+
+	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 user node.
+ */
+int of_hwspin_lock_get_id(struct device_node *np, int index)
+{
+	struct hwspinlock_device *bank;
+	struct of_phandle_args args;
+	int id;
+	int ret;
+
+	ret = of_parse_phandle_with_args(np, "hwlocks", "#hwlock-cells", index,
+					 &args);
+	if (ret)
+		return ret;
+
+	mutex_lock(&hwspinlock_tree_lock);
+	list_for_each_entry(bank, &hwspinlock_devices, list)
+		if (bank->dev->of_node == args.np)
+			break;
+	mutex_unlock(&hwspinlock_tree_lock);
+	if (&bank->list == &hwspinlock_devices) {
+		ret = -EPROBE_DEFER;
+		goto out;
+	}
+
+	id = of_hwspin_lock_simple_xlate(bank, &args);
+	if (id < 0 || id >= bank->num_locks) {
+		ret = -EINVAL;
+		goto out;
+	}
+	id += bank->base_id;
+
+out:
+	of_node_put(args.np);
+	return ret ? ret : id;
+}
+EXPORT_SYMBOL_GPL(of_hwspin_lock_get_id);
+
+/**
+ * of_hwspin_lock_get_base_id() - OF helper to retrieve base id
+ * @dn: device node pointer
+ *
+ * This is an OF helper function that can be called by the underlying
+ * platform-specific implementations, to retrieve the base id for the
+ * set of locks present within a hwspinlock device instance.
+ *
+ * Returns the base id value on success, or an appropriate error code
+ * as returned by the OF layer
+ */
+int of_hwspin_lock_get_base_id(struct device_node *dn)
+{
+	unsigned int val;
+	int ret;
+
+	ret = of_property_read_u32(dn, "hwlock-base-id", &val);
+	return ret ? ret : val;
+}
+EXPORT_SYMBOL_GPL(of_hwspin_lock_get_base_id);
+
+/**
+ * of_hwspin_lock_get_num_locks() - OF helper to retrieve number of 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
+ * present within a hwspinlock device instance. The hwlock-num-locks
+ * DT property may be optional for some platforms, while mandatory for
+ * some others, so this function is typically called only by needed
+ * platform-specific implementations.
+ *
+ * Returns a positive number of locks on success, -ENODEV on generic
+ * failure or an appropriate error code as returned by the OF layer
+ */
+int of_hwspin_lock_get_num_locks(struct device_node *dn)
+{
+	unsigned int val;
+	int ret = -ENODEV;
+
+	ret = of_property_read_u32(dn, "hwlock-num-locks", &val);
+	if (!ret)
+		ret = val ? val : -ENODEV;
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(of_hwspin_lock_get_num_locks);
+
 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 3343298..a9eeb4f 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;
@@ -60,12 +61,15 @@ struct hwspinlock_pdata {
 
 #if defined(CONFIG_HWSPINLOCK) || defined(CONFIG_HWSPINLOCK_MODULE)
 
+int of_hwspin_lock_get_base_id(struct device_node *dn);
+int of_hwspin_lock_get_num_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 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 *);
@@ -80,9 +84,9 @@ void __hwspin_unlock(struct hwspinlock *, int, unsigned long *);
  * code path get compiled away. This way, if CONFIG_HWSPINLOCK is not
  * required on a given setup, users will still work.
  *
- * The only exception is hwspin_lock_register/hwspin_lock_unregister, with which
- * we _do_ want users to fail (no point in registering hwspinlock instances if
- * the framework is not available).
+ * The only exception is hwspin_lock_register/hwspin_lock_unregister and
+ * associated OF helpers, with which we _do_ want users to fail (no point
+ * in registering hwspinlock instances if the framework is not available).
  *
  * Note: ERR_PTR(-ENODEV) will still be considered a success for NULL-checking
  * users. Others, which care, can still check this with IS_ERR.
@@ -120,6 +124,11 @@ 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;
-- 
2.0.4

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