hwspinlock/core: register a bank of hwspinlocks in a single API call

Hardware Spinlock devices usually contain numerous locks (known
devices today support between 32 to 256 locks).

Originally hwspinlock core required drivers to register (and later,
when needed, unregister) each lock separately.

That worked, but required hwspinlocks drivers to do a bit extra work
when they were probed/removed.

This patch changes hwspin_lock_{un}register() to allow a bank of
hwspinlocks to be {un}registered in a single invocation.

A new 'struct hwspinlock_device', which contains an array of 'struct
hwspinlock's is now being passed to the core upon registration (so
instead of wrapping each struct hwspinlock, a priv member has been added
to allow drivers to piggyback their private data with each hwspinlock).

While at it, several per-lock members were moved to be per-device:
1. struct device *dev
2. struct hwspinlock_ops *ops

In addition, now that the array of locks is handled by the core,
there's no reason to maintain a per-lock 'int id' member: the id of the
lock anyway equals to its index in the bank's array plus the bank's
base_id.
Remove this per-lock id member too, and instead use a simple pointers
arithmetic to derive it.

As a result of this change, hwspinlocks drivers are now simpler and smaller
(about %20 code reduction) and the memory footprint of the hwspinlock
framework is reduced.

Signed-off-by: Ohad Ben-Cohen <ohad@wizery.com>

1 files changed, 28 insertions, 10 deletions

diff --git a/drivers/hwspinlock/hwspinlock_internal.h b/drivers/hwspinlock/hwspinlock_internal.h
index fb25830c2ee7..d26f78b8f214 100644
--- a/drivers/hwspinlock/hwspinlock_internal.h
+++ b/drivers/hwspinlock/hwspinlock_internal.h
@@ -21,6 +21,8 @@
 #include <linux/spinlock.h>
 #include <linux/device.h>
 
+struct hwspinlock_device;
+
 /**
  * struct hwspinlock_ops - platform-specific hwspinlock handlers
  *
@@ -39,21 +41,37 @@ struct hwspinlock_ops {
 
 /**
  * struct hwspinlock - this struct represents a single hwspinlock instance
- *
- * @dev: underlying device, will be used to invoke runtime PM api
- * @ops: platform-specific hwspinlock handlers
- * @id: a global, unique, system-wide, index of the lock.
+ * @bank: the hwspinlock_device structure which owns this lock
  * @lock: initialized and used by hwspinlock core
- *
- * Note: currently simplicity was opted for, but later we can squeeze some
- * memory bytes by grouping dev, ops in a single
- * per-platform struct, and have all hwspinlocks point at it.
+ * @priv: private data, owned by the underlying platform-specific hwspinlock drv
  */
 struct hwspinlock {
+	struct hwspinlock_device *bank;
+	spinlock_t lock;
+	void *priv;
+};
+
+/**
+ * struct hwspinlock_device - a device which usually spans numerous hwspinlocks
+ * @dev: underlying device, will be used to invoke runtime PM api
+ * @ops: platform-specific hwspinlock handlers
+ * @base_id: id index of the first lock in this device
+ * @num_locks: number of locks in this device
+ * @lock: dynamically allocated array of 'struct hwspinlock'
+ */
+struct hwspinlock_device {
 	struct device *dev;
 	const struct hwspinlock_ops *ops;
-	int id;
-	spinlock_t lock;
+	int base_id;
+	int num_locks;
+	struct hwspinlock lock[0];
 };
 
+static inline int hwlock_to_id(struct hwspinlock *hwlock)
+{
+	int local_id = hwlock - &hwlock->bank->lock[0];
+
+	return hwlock->bank->base_id + local_id;
+}
+
 #endif /* __HWSPINLOCK_HWSPINLOCK_H */