arm64: locking: Replace ticket lock implementation with qspinlock

It's fair to say that our ticket lock has served us well over time, but
it's time to bite the bullet and start using the generic qspinlock code
so we can make use of explicit MCS queuing and potentially better PV
performance in future.

Signed-off-by: Will Deacon <will.deacon@arm.com>

1 files changed, 1 insertions, 116 deletions

diff --git a/arch/arm64/include/asm/spinlock.h b/arch/arm64/include/asm/spinlock.h
index 26c5bd7d88d8..38116008d18b 100644
--- a/arch/arm64/include/asm/spinlock.h
+++ b/arch/arm64/include/asm/spinlock.h
@@ -16,123 +16,8 @@
 #ifndef __ASM_SPINLOCK_H
 #define __ASM_SPINLOCK_H
 
-#include <asm/lse.h>
-#include <asm/spinlock_types.h>
-#include <asm/processor.h>
-
-/*
- * Spinlock implementation.
- *
- * The memory barriers are implicit with the load-acquire and store-release
- * instructions.
- */
-
-static inline void arch_spin_lock(arch_spinlock_t *lock)
-{
-	unsigned int tmp;
-	arch_spinlock_t lockval, newval;
-
-	asm volatile(
-	/* Atomically increment the next ticket. */
-	ARM64_LSE_ATOMIC_INSN(
-	/* LL/SC */
-"	prfm	pstl1strm, %3\n"
-"1:	ldaxr	%w0, %3\n"
-"	add	%w1, %w0, %w5\n"
-"	stxr	%w2, %w1, %3\n"
-"	cbnz	%w2, 1b\n",
-	/* LSE atomics */
-"	mov	%w2, %w5\n"
-"	ldadda	%w2, %w0, %3\n"
-	__nops(3)
-	)
-
-	/* Did we get the lock? */
-"	eor	%w1, %w0, %w0, ror #16\n"
-"	cbz	%w1, 3f\n"
-	/*
-	 * No: spin on the owner. Send a local event to avoid missing an
-	 * unlock before the exclusive load.
-	 */
-"	sevl\n"
-"2:	wfe\n"
-"	ldaxrh	%w2, %4\n"
-"	eor	%w1, %w2, %w0, lsr #16\n"
-"	cbnz	%w1, 2b\n"
-	/* We got the lock. Critical section starts here. */
-"3:"
-	: "=&r" (lockval), "=&r" (newval), "=&r" (tmp), "+Q" (*lock)
-	: "Q" (lock->owner), "I" (1 << TICKET_SHIFT)
-	: "memory");
-}
-
-static inline int arch_spin_trylock(arch_spinlock_t *lock)
-{
-	unsigned int tmp;
-	arch_spinlock_t lockval;
-
-	asm volatile(ARM64_LSE_ATOMIC_INSN(
-	/* LL/SC */
-	"	prfm	pstl1strm, %2\n"
-	"1:	ldaxr	%w0, %2\n"
-	"	eor	%w1, %w0, %w0, ror #16\n"
-	"	cbnz	%w1, 2f\n"
-	"	add	%w0, %w0, %3\n"
-	"	stxr	%w1, %w0, %2\n"
-	"	cbnz	%w1, 1b\n"
-	"2:",
-	/* LSE atomics */
-	"	ldr	%w0, %2\n"
-	"	eor	%w1, %w0, %w0, ror #16\n"
-	"	cbnz	%w1, 1f\n"
-	"	add	%w1, %w0, %3\n"
-	"	casa	%w0, %w1, %2\n"
-	"	sub	%w1, %w1, %3\n"
-	"	eor	%w1, %w1, %w0\n"
-	"1:")
-	: "=&r" (lockval), "=&r" (tmp), "+Q" (*lock)
-	: "I" (1 << TICKET_SHIFT)
-	: "memory");
-
-	return !tmp;
-}
-
-static inline void arch_spin_unlock(arch_spinlock_t *lock)
-{
-	unsigned long tmp;
-
-	asm volatile(ARM64_LSE_ATOMIC_INSN(
-	/* LL/SC */
-	"	ldrh	%w1, %0\n"
-	"	add	%w1, %w1, #1\n"
-	"	stlrh	%w1, %0",
-	/* LSE atomics */
-	"	mov	%w1, #1\n"
-	"	staddlh	%w1, %0\n"
-	__nops(1))
-	: "=Q" (lock->owner), "=&r" (tmp)
-	:
-	: "memory");
-}
-
-static inline int arch_spin_value_unlocked(arch_spinlock_t lock)
-{
-	return lock.owner == lock.next;
-}
-
-static inline int arch_spin_is_locked(arch_spinlock_t *lock)
-{
-	return !arch_spin_value_unlocked(READ_ONCE(*lock));
-}
-
-static inline int arch_spin_is_contended(arch_spinlock_t *lock)
-{
-	arch_spinlock_t lockval = READ_ONCE(*lock);
-	return (lockval.next - lockval.owner) > 1;
-}
-#define arch_spin_is_contended	arch_spin_is_contended
-
 #include <asm/qrwlock.h>
+#include <asm/qspinlock.h>
 
 /* See include/linux/spinlock.h */
 #define smp_mb__after_spinlock()	smp_mb()