1 files changed, 169 insertions, 0 deletions

diff --git a/include/asm-arm/spinlock.h b/include/asm-arm/spinlock.h
new file mode 100644
index 000000000000..182323619caa
--- /dev/null
+++ b/include/asm-arm/spinlock.h
@@ -0,0 +1,169 @@
+#ifndef __ASM_SPINLOCK_H
+#define __ASM_SPINLOCK_H
+
+#if __LINUX_ARM_ARCH__ < 6
+#error SMP not supported on pre-ARMv6 CPUs
+#endif
+
+/*
+ * ARMv6 Spin-locking.
+ *
+ * We (exclusively) read the old value, and decrement it.  If it
+ * hits zero, we may have won the lock, so we try (exclusively)
+ * storing it.
+ *
+ * Unlocked value: 0
+ * Locked value: 1
+ */
+typedef struct {
+        volatile unsigned int lock;
+#ifdef CONFIG_PREEMPT
+        unsigned int break_lock;
+#endif
+} spinlock_t;
+
+#define SPIN_LOCK_UNLOCKED      (spinlock_t) { 0 }
+
+#define spin_lock_init(x)       do { *(x) = SPIN_LOCK_UNLOCKED; } while (0)
+#define spin_is_locked(x)       ((x)->lock != 0)
+#define spin_unlock_wait(x)     do { barrier(); } while (spin_is_locked(x))
+#define _raw_spin_lock_flags(lock, flags) _raw_spin_lock(lock)
+
+static inline void _raw_spin_lock(spinlock_t *lock)
+{
+        unsigned long tmp;
+
+        __asm__ __volatile__(
+"1:     ldrex   %0, [%1]\n"
+"       teq     %0, #0\n"
+"       strexeq %0, %2, [%1]\n"
+"       teqeq   %0, #0\n"
+"       bne     1b"
+        : "=&r" (tmp)
+        : "r" (&lock->lock), "r" (1)
+        : "cc", "memory");
+}
+
+static inline int _raw_spin_trylock(spinlock_t *lock)
+{
+        unsigned long tmp;
+
+        __asm__ __volatile__(
+"       ldrex   %0, [%1]\n"
+"       teq     %0, #0\n"
+"       strexeq %0, %2, [%1]"
+        : "=&r" (tmp)
+        : "r" (&lock->lock), "r" (1)
+        : "cc", "memory");
+
+        return tmp == 0;
+}
+
+static inline void _raw_spin_unlock(spinlock_t *lock)
+{
+        __asm__ __volatile__(
+"       str     %1, [%0]"
+        :
+        : "r" (&lock->lock), "r" (0)
+        : "cc", "memory");
+}
+
+/*
+ * RWLOCKS
+ */
+typedef struct {
+        volatile unsigned int lock;
+#ifdef CONFIG_PREEMPT
+        unsigned int break_lock;
+#endif
+} rwlock_t;
+
+#define RW_LOCK_UNLOCKED        (rwlock_t) { 0 }
+#define rwlock_init(x)          do { *(x) + RW_LOCK_UNLOCKED; } while (0)
+
+/*
+ * Write locks are easy - we just set bit 31.  When unlocking, we can
+ * just write zero since the lock is exclusively held.
+ */
+static inline void _raw_write_lock(rwlock_t *rw)
+{
+        unsigned long tmp;
+
+        __asm__ __volatile__(
+"1:     ldrex   %0, [%1]\n"
+"       teq     %0, #0\n"
+"       strexeq %0, %2, [%1]\n"
+"       teq     %0, #0\n"
+"       bne     1b"
+        : "=&r" (tmp)
+        : "r" (&rw->lock), "r" (0x80000000)
+        : "cc", "memory");
+}
+
+static inline void _raw_write_unlock(rwlock_t *rw)
+{
+        __asm__ __volatile__(
+        "str    %1, [%0]"
+        :
+        : "r" (&rw->lock), "r" (0)
+        : "cc", "memory");
+}
+
+/*
+ * Read locks are a bit more hairy:
+ *  - Exclusively load the lock value.
+ *  - Increment it.
+ *  - Store new lock value if positive, and we still own this location.
+ *    If the value is negative, we've already failed.
+ *  - If we failed to store the value, we want a negative result.
+ *  - If we failed, try again.
+ * Unlocking is similarly hairy.  We may have multiple read locks
+ * currently active.  However, we know we won't have any write
+ * locks.
+ */
+static inline void _raw_read_lock(rwlock_t *rw)
+{
+        unsigned long tmp, tmp2;
+
+        __asm__ __volatile__(
+"1:     ldrex   %0, [%2]\n"
+"       adds    %0, %0, #1\n"
+"       strexpl %1, %0, [%2]\n"
+"       rsbpls  %0, %1, #0\n"
+"       bmi     1b"
+        : "=&r" (tmp), "=&r" (tmp2)
+        : "r" (&rw->lock)
+        : "cc", "memory");
+}
+
+static inline void _raw_read_unlock(rwlock_t *rw)
+{
+        __asm__ __volatile__(
+"1:     ldrex   %0, [%2]\n"
+"       sub     %0, %0, #1\n"
+"       strex   %1, %0, [%2]\n"
+"       teq     %1, #0\n"
+"       bne     1b"
+        : "=&r" (tmp), "=&r" (tmp2)
+        : "r" (&rw->lock)
+        : "cc", "memory");
+}
+
+#define _raw_read_trylock(lock) generic_raw_read_trylock(lock)
+
+static inline int _raw_write_trylock(rwlock_t *rw)
+{
+        unsigned long tmp;
+
+        __asm__ __volatile__(
+"1:     ldrex   %0, [%1]\n"
+"       teq     %0, #0\n"
+"       strexeq %0, %2, [%1]"
+        : "=&r" (tmp)
+        : "r" (&rw->lock), "r" (0x80000000)
+        : "cc", "memory");
+
+        return tmp == 0;
+}
+
+#endif /* __ASM_SPINLOCK_H */