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authorRussell King <rmk@dyn-67.arm.linux.org.uk>2008-08-02 10:55:55 +0100
committerRussell King <rmk+kernel@arm.linux.org.uk>2008-08-02 21:32:35 +0100
commit4baa9922430662431231ac637adedddbb0cfb2d7 (patch)
treee8fb765ce3e41c01f33de34a0bc9494f0ae19818 /arch/arm/include/asm/spinlock.h
parentff4db0a043a5dee7180bdffd178e61cd02812c68 (diff)
downloadlinux-4baa9922430662431231ac637adedddbb0cfb2d7.tar.gz
[ARM] move include/asm-arm to arch/arm/include/asm
Move platform independent header files to arch/arm/include/asm, leaving those in asm/arch* and asm/plat* alone. Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Diffstat (limited to 'arch/arm/include/asm/spinlock.h')
-rw-r--r--arch/arm/include/asm/spinlock.h224
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 00000000000..2b41ebbfa7f
--- /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 */