1 files changed, 224 insertions, 0 deletions

diff --git a/arch/arm/include/asm/spinlock.h b/arch/arm/include/asm/spinlock.h
new file mode 100644
index 000000000000..2b41ebbfa7ff
--- /dev/null
+++ b/arch/arm/include/asm/spinlock.h
@@ -0,0 +1,224 @@
+#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.  If it is zero, we may have
+ * won the lock, so we try exclusively storing it.  A memory barrier
+ * is required after we get a lock, and before we release it, because
+ * V6 CPUs are assumed to have weakly ordered memory.
+ *
+ * Unlocked value: 0
+ * Locked value: 1
+ */
+
+#define __raw_spin_is_locked(x)         ((x)->lock != 0)
+#define __raw_spin_unlock_wait(lock) \
+        do { while (__raw_spin_is_locked(lock)) cpu_relax(); } while (0)
+
+#define __raw_spin_lock_flags(lock, flags) __raw_spin_lock(lock)
+
+static inline void __raw_spin_lock(raw_spinlock_t *lock)
+{
+        unsigned long tmp;
+
+        __asm__ __volatile__(
+"1:     ldrex   %0, [%1]\n"
+"       teq     %0, #0\n"
+#ifdef CONFIG_CPU_32v6K
+"       wfene\n"
+#endif
+"       strexeq %0, %2, [%1]\n"
+"       teqeq   %0, #0\n"
+"       bne     1b"
+        : "=&r" (tmp)
+        : "r" (&lock->lock), "r" (1)
+        : "cc");
+
+        smp_mb();
+}
+
+static inline int __raw_spin_trylock(raw_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");
+
+        if (tmp == 0) {
+                smp_mb();
+                return 1;
+        } else {
+                return 0;
+        }
+}
+
+static inline void __raw_spin_unlock(raw_spinlock_t *lock)
+{
+        smp_mb();
+
+        __asm__ __volatile__(
+"       str     %1, [%0]\n"
+#ifdef CONFIG_CPU_32v6K
+"       mcr     p15, 0, %1, c7, c10, 4\n" /* DSB */
+"       sev"
+#endif
+        :
+        : "r" (&lock->lock), "r" (0)
+        : "cc");
+}
+
+/*
+ * RWLOCKS
+ *
+ *
+ * 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(raw_rwlock_t *rw)
+{
+        unsigned long tmp;
+
+        __asm__ __volatile__(
+"1:     ldrex   %0, [%1]\n"
+"       teq     %0, #0\n"
+#ifdef CONFIG_CPU_32v6K
+"       wfene\n"
+#endif
+"       strexeq %0, %2, [%1]\n"
+"       teq     %0, #0\n"
+"       bne     1b"
+        : "=&r" (tmp)
+        : "r" (&rw->lock), "r" (0x80000000)
+        : "cc");
+
+        smp_mb();
+}
+
+static inline int __raw_write_trylock(raw_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");
+
+        if (tmp == 0) {
+                smp_mb();
+                return 1;
+        } else {
+                return 0;
+        }
+}
+
+static inline void __raw_write_unlock(raw_rwlock_t *rw)
+{
+        smp_mb();
+
+        __asm__ __volatile__(
+        "str    %1, [%0]\n"
+#ifdef CONFIG_CPU_32v6K
+"       mcr     p15, 0, %1, c7, c10, 4\n" /* DSB */
+"       sev\n"
+#endif
+        :
+        : "r" (&rw->lock), "r" (0)
+        : "cc");
+}
+
+/* write_can_lock - would write_trylock() succeed? */
+#define __raw_write_can_lock(x)         ((x)->lock == 0)
+
+/*
+ * 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(raw_rwlock_t *rw)
+{
+        unsigned long tmp, tmp2;
+
+        __asm__ __volatile__(
+"1:     ldrex   %0, [%2]\n"
+"       adds    %0, %0, #1\n"
+"       strexpl %1, %0, [%2]\n"
+#ifdef CONFIG_CPU_32v6K
+"       wfemi\n"
+#endif
+"       rsbpls  %0, %1, #0\n"
+"       bmi     1b"
+        : "=&r" (tmp), "=&r" (tmp2)
+        : "r" (&rw->lock)
+        : "cc");
+
+        smp_mb();
+}
+
+static inline void __raw_read_unlock(raw_rwlock_t *rw)
+{
+        unsigned long tmp, tmp2;
+
+        smp_mb();
+
+        __asm__ __volatile__(
+"1:     ldrex   %0, [%2]\n"
+"       sub     %0, %0, #1\n"
+"       strex   %1, %0, [%2]\n"
+"       teq     %1, #0\n"
+"       bne     1b"
+#ifdef CONFIG_CPU_32v6K
+"\n     cmp     %0, #0\n"
+"       mcreq   p15, 0, %0, c7, c10, 4\n"
+"       seveq"
+#endif
+        : "=&r" (tmp), "=&r" (tmp2)
+        : "r" (&rw->lock)
+        : "cc");
+}
+
+static inline int __raw_read_trylock(raw_rwlock_t *rw)
+{
+        unsigned long tmp, tmp2 = 1;
+
+        __asm__ __volatile__(
+"1:     ldrex   %0, [%2]\n"
+"       adds    %0, %0, #1\n"
+"       strexpl %1, %0, [%2]\n"
+        : "=&r" (tmp), "+r" (tmp2)
+        : "r" (&rw->lock)
+        : "cc");
+
+        smp_mb();
+        return tmp2 == 0;
+}
+
+/* read_can_lock - would read_trylock() succeed? */
+#define __raw_read_can_lock(x)          ((x)->lock < 0x80000000)
+
+#define _raw_spin_relax(lock)   cpu_relax()
+#define _raw_read_relax(lock)   cpu_relax()
+#define _raw_write_relax(lock)  cpu_relax()
+
+#endif /* __ASM_SPINLOCK_H */