linux/arch/mips/include/asm/spinlock.h

/*
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file "COPYING" in the main directory of this archive
 * for more details.
 *
 * Copyright (C) 1999, 2000, 06 Ralf Baechle (ralf@linux-mips.org)
 * Copyright (C) 1999, 2000 Silicon Graphics, Inc.
 */
#ifndef _ASM_SPINLOCK_H
#define _ASM_SPINLOCK_H

#include <linux/compiler.h>

#include <asm/barrier.h>
#include <asm/compiler.h>
#include <asm/war.h>

/*
 * Your basic SMP spinlocks, allowing only a single CPU anywhere
 *
 * Simple spin lock operations.	 There are two variants, one clears IRQ's
 * on the local processor, one does not.
 *
 * These are fair FIFO ticket locks
 *
 * (the type definitions are in asm/spinlock_types.h)
 */


/*
 * Ticket locks are conceptually two parts, one indicating the current head of
 * the queue, and the other indicating the current tail. The lock is acquired
 * by atomically noting the tail and incrementing it by one (thus adding
 * ourself to the queue and noting our position), then waiting until the head
 * becomes equal to the the initial value of the tail.
 */

static inline int arch_spin_is_locked(arch_spinlock_t *lock)
{
	u32 counters = ACCESS_ONCE(lock->lock);

	return ((counters >> 16) ^ counters) & 0xffff;
}

#define arch_spin_lock_flags(lock, flags) arch_spin_lock(lock)
#define arch_spin_unlock_wait(x) \
	while (arch_spin_is_locked(x)) { cpu_relax(); }

static inline int arch_spin_is_contended(arch_spinlock_t *lock)
{
	u32 counters = ACCESS_ONCE(lock->lock);

	return (((counters >> 16) - counters) & 0xffff) > 1;
}
#define arch_spin_is_contended	arch_spin_is_contended

static inline void arch_spin_lock(arch_spinlock_t *lock)
{
	int my_ticket;
	int tmp;
	int inc = 0x10000;

	if (R10000_LLSC_WAR) {
		__asm__ __volatile__ (
		"	.set push		# arch_spin_lock	\n"
		"	.set noreorder					\n"
		"							\n"
		"1:	ll	%[ticket], %[ticket_ptr]		\n"
		"	addu	%[my_ticket], %[ticket], %[inc]		\n"
		"	sc	%[my_ticket], %[ticket_ptr]		\n"
		"	beqzl	%[my_ticket], 1b			\n"
		"	 nop						\n"
		"	srl	%[my_ticket], %[ticket], 16		\n"
		"	andi	%[ticket], %[ticket], 0xffff		\n"
		"	bne	%[ticket], %[my_ticket], 4f		\n"
		"	 subu	%[ticket], %[my_ticket], %[ticket]	\n"
		"2:							\n"
		"	.subsection 2					\n"
		"4:	andi	%[ticket], %[ticket], 0xffff		\n"
		"	sll	%[ticket], 5				\n"
		"							\n"
		"6:	bnez	%[ticket], 6b				\n"
		"	 subu	%[ticket], 1				\n"
		"							\n"
		"	lhu	%[ticket], %[serving_now_ptr]		\n"
		"	beq	%[ticket], %[my_ticket], 2b		\n"
		"	 subu	%[ticket], %[my_ticket], %[ticket]	\n"
		"	b	4b					\n"
		"	 subu	%[ticket], %[ticket], 1			\n"
		"	.previous					\n"
		"	.set pop					\n"
		: [ticket_ptr] "+" GCC_OFF_SMALL_ASM() (lock->lock),
		  [serving_now_ptr] "+m" (lock->h.serving_now),
		  [ticket] "=&r" (tmp),
		  [my_ticket] "=&r" (my_ticket)
		: [inc] "r" (inc));
	} else {
		__asm__ __volatile__ (
		"	.set push		# arch_spin_lock	\n"
		"	.set noreorder					\n"
		"							\n"
		"1:	ll	%[ticket], %[ticket_ptr]		\n"
		"	addu	%[my_ticket], %[ticket], %[inc]		\n"
		"	sc	%[my_ticket], %[ticket_ptr]		\n"
		"	beqz	%[my_ticket], 1b			\n"
		"	 srl	%[my_ticket], %[ticket], 16		\n"
		"	andi	%[ticket], %[ticket], 0xffff		\n"
		"	bne	%[ticket], %[my_ticket], 4f		\n"
		"	 subu	%[ticket], %[my_ticket], %[ticket]	\n"
		"2:							\n"
		"	.subsection 2					\n"
		"4:	andi	%[ticket], %[ticket], 0xffff		\n"
		"	sll	%[ticket], 5				\n"
		"							\n"
		"6:	bnez	%[ticket], 6b				\n"
		"	 subu	%[ticket], 1				\n"
		"							\n"
		"	lhu	%[ticket], %[serving_now_ptr]		\n"
		"	beq	%[ticket], %[my_ticket], 2b		\n"
		"	 subu	%[ticket], %[my_ticket], %[ticket]	\n"
		"	b	4b					\n"
		"	 subu	%[ticket], %[ticket], 1			\n"
		"	.previous					\n"
		"	.set pop					\n"
		: [ticket_ptr] "+" GCC_OFF_SMALL_ASM() (lock->lock),
		  [serving_now_ptr] "+m" (lock->h.serving_now),
		  [ticket] "=&r" (tmp),
		  [my_ticket] "=&r" (my_ticket)
		: [inc] "r" (inc));
	}

	smp_llsc_mb();
}

static inline void arch_spin_unlock(arch_spinlock_t *lock)
{
	unsigned int serving_now = lock->h.serving_now + 1;
	wmb();
	lock->h.serving_now = (u16)serving_now;
	nudge_writes();
}

static inline unsigned int arch_spin_trylock(arch_spinlock_t *lock)
{
	int tmp, tmp2, tmp3;
	int inc = 0x10000;

	if (R10000_LLSC_WAR) {
		__asm__ __volatile__ (
		"	.set push		# arch_spin_trylock	\n"
		"	.set noreorder					\n"
		"							\n"
		"1:	ll	%[ticket], %[ticket_ptr]		\n"
		"	srl	%[my_ticket], %[ticket], 16		\n"
		"	andi	%[now_serving], %[ticket], 0xffff	\n"
		"	bne	%[my_ticket], %[now_serving], 3f	\n"
		"	 addu	%[ticket], %[ticket], %[inc]		\n"
		"	sc	%[ticket], %[ticket_ptr]		\n"
		"	beqzl	%[ticket], 1b				\n"
		"	 li	%[ticket], 1				\n"
		"2:							\n"
		"	.subsection 2					\n"
		"3:	b	2b					\n"
		"	 li	%[ticket], 0				\n"
		"	.previous					\n"
		"	.set pop					\n"
		: [ticket_ptr] "+" GCC_OFF_SMALL_ASM() (lock->lock),
		  [ticket] "=&r" (tmp),
		  [my_ticket] "=&r" (tmp2),
		  [now_serving] "=&r" (tmp3)
		: [inc] "r" (inc));
	} else {
		__asm__ __volatile__ (
		"	.set push		# arch_spin_trylock	\n"
		"	.set noreorder					\n"
		"							\n"
		"1:	ll	%[ticket], %[ticket_ptr]		\n"
		"	srl	%[my_ticket], %[ticket], 16		\n"
		"	andi	%[now_serving], %[ticket], 0xffff	\n"
		"	bne	%[my_ticket], %[now_serving], 3f	\n"
		"	 addu	%[ticket], %[ticket], %[inc]		\n"
		"	sc	%[ticket], %[ticket_ptr]		\n"
		"	beqz	%[ticket], 1b				\n"
		"	 li	%[ticket], 1				\n"
		"2:							\n"
		"	.subsection 2					\n"
		"3:	b	2b					\n"
		"	 li	%[ticket], 0				\n"
		"	.previous					\n"
		"	.set pop					\n"
		: [ticket_ptr] "+" GCC_OFF_SMALL_ASM() (lock->lock),
		  [ticket] "=&r" (tmp),
		  [my_ticket] "=&r" (tmp2),
		  [now_serving] "=&r" (tmp3)
		: [inc] "r" (inc));
	}

	smp_llsc_mb();

	return tmp;
}

/*
 * Read-write spinlocks, allowing multiple readers but only one writer.
 *
 * NOTE! it is quite common to have readers in interrupts but no interrupt
 * writers. For those circumstances we can "mix" irq-safe locks - any writer
 * needs to get a irq-safe write-lock, but readers can get non-irqsafe
 * read-locks.
 */

/*
 * read_can_lock - would read_trylock() succeed?
 * @lock: the rwlock in question.
 */
#define arch_read_can_lock(rw)	((rw)->lock >= 0)

/*
 * write_can_lock - would write_trylock() succeed?
 * @lock: the rwlock in question.
 */
#define arch_write_can_lock(rw) (!(rw)->lock)

static inline void arch_read_lock(arch_rwlock_t *rw)
{
	unsigned int tmp;

	if (R10000_LLSC_WAR) {
		__asm__ __volatile__(
		"	.set	noreorder	# arch_read_lock	\n"
		"1:	ll	%1, %2					\n"
		"	bltz	%1, 1b					\n"
		"	 addu	%1, 1					\n"
		"	sc	%1, %0					\n"
		"	beqzl	%1, 1b					\n"
		"	 nop						\n"
		"	.set	reorder					\n"
		: "=" GCC_OFF_SMALL_ASM() (rw->lock), "=&r" (tmp)
		: GCC_OFF_SMALL_ASM() (rw->lock)
		: "memory");
	} else {
		do {
			__asm__ __volatile__(
			"1:	ll	%1, %2	# arch_read_lock	\n"
			"	bltz	%1, 1b				\n"
			"	 addu	%1, 1				\n"
			"2:	sc	%1, %0				\n"
			: "=" GCC_OFF_SMALL_ASM() (rw->lock), "=&r" (tmp)
			: GCC_OFF_SMALL_ASM() (rw->lock)
			: "memory");
		} while (unlikely(!tmp));
	}

	smp_llsc_mb();
}

static inline void arch_read_unlock(arch_rwlock_t *rw)
{
	unsigned int tmp;

	smp_mb__before_llsc();

	if (R10000_LLSC_WAR) {
		__asm__ __volatile__(
		"1:	ll	%1, %2		# arch_read_unlock	\n"
		"	addiu	%1, -1					\n"
		"	sc	%1, %0					\n"
		"	beqzl	%1, 1b					\n"
		: "=" GCC_OFF_SMALL_ASM() (rw->lock), "=&r" (tmp)
		: GCC_OFF_SMALL_ASM() (rw->lock)
		: "memory");
	} else {
		do {
			__asm__ __volatile__(
			"1:	ll	%1, %2	# arch_read_unlock	\n"
			"	addiu	%1, -1				\n"
			"	sc	%1, %0				\n"
			: "=" GCC_OFF_SMALL_ASM() (rw->lock), "=&r" (tmp)
			: GCC_OFF_SMALL_ASM() (rw->lock)
			: "memory");
		} while (unlikely(!tmp));
	}
}

static inline void arch_write_lock(arch_rwlock_t *rw)
{
	unsigned int tmp;

	if (R10000_LLSC_WAR) {
		__asm__ __volatile__(
		"	.set	noreorder	# arch_write_lock	\n"
		"1:	ll	%1, %2					\n"
		"	bnez	%1, 1b					\n"
		"	 lui	%1, 0x8000				\n"
		"	sc	%1, %0					\n"
		"	beqzl	%1, 1b					\n"
		"	 nop						\n"
		"	.set	reorder					\n"
		: "=" GCC_OFF_SMALL_ASM() (rw->lock), "=&r" (tmp)
		: GCC_OFF_SMALL_ASM() (rw->lock)
		: "memory");
	} else {
		do {
			__asm__ __volatile__(
			"1:	ll	%1, %2	# arch_write_lock	\n"
			"	bnez	%1, 1b				\n"
			"	 lui	%1, 0x8000			\n"
			"2:	sc	%1, %0				\n"
			: "=" GCC_OFF_SMALL_ASM() (rw->lock), "=&r" (tmp)
			: GCC_OFF_SMALL_ASM() (rw->lock)
			: "memory");
		} while (unlikely(!tmp));
	}

	smp_llsc_mb();
}

static inline void arch_write_unlock(arch_rwlock_t *rw)
{
	smp_mb__before_llsc();

	__asm__ __volatile__(
	"				# arch_write_unlock	\n"
	"	sw	$0, %0					\n"
	: "=m" (rw->lock)
	: "m" (rw->lock)
	: "memory");
}

static inline int arch_read_trylock(arch_rwlock_t *rw)
{
	unsigned int tmp;
	int ret;

	if (R10000_LLSC_WAR) {
		__asm__ __volatile__(
		"	.set	noreorder	# arch_read_trylock	\n"
		"	li	%2, 0					\n"
		"1:	ll	%1, %3					\n"
		"	bltz	%1, 2f					\n"
		"	 addu	%1, 1					\n"
		"	sc	%1, %0					\n"
		"	.set	reorder					\n"
		"	beqzl	%1, 1b					\n"
		"	 nop						\n"
		__WEAK_LLSC_MB
		"	li	%2, 1					\n"
		"2:							\n"
		: "=" GCC_OFF_SMALL_ASM() (rw->lock), "=&r" (tmp), "=&r" (ret)
		: GCC_OFF_SMALL_ASM() (rw->lock)
		: "memory");
	} else {
		__asm__ __volatile__(
		"	.set	noreorder	# arch_read_trylock	\n"
		"	li	%2, 0					\n"
		"1:	ll	%1, %3					\n"
		"	bltz	%1, 2f					\n"
		"	 addu	%1, 1					\n"
		"	sc	%1, %0					\n"
		"	beqz	%1, 1b					\n"
		"	 nop						\n"
		"	.set	reorder					\n"
		__WEAK_LLSC_MB
		"	li	%2, 1					\n"
		"2:							\n"
		: "=" GCC_OFF_SMALL_ASM() (rw->lock), "=&r" (tmp), "=&r" (ret)
		: GCC_OFF_SMALL_ASM() (rw->lock)
		: "memory");
	}

	return ret;
}

static inline int arch_write_trylock(arch_rwlock_t *rw)
{
	unsigned int tmp;
	int ret;

	if (R10000_LLSC_WAR) {
		__asm__ __volatile__(
		"	.set	noreorder	# arch_write_trylock	\n"
		"	li	%2, 0					\n"
		"1:	ll	%1, %3					\n"
		"	bnez	%1, 2f					\n"
		"	 lui	%1, 0x8000				\n"
		"	sc	%1, %0					\n"
		"	beqzl	%1, 1b					\n"
		"	 nop						\n"
		__WEAK_LLSC_MB
		"	li	%2, 1					\n"
		"	.set	reorder					\n"
		"2:							\n"
		: "=" GCC_OFF_SMALL_ASM() (rw->lock), "=&r" (tmp), "=&r" (ret)
		: GCC_OFF_SMALL_ASM() (rw->lock)
		: "memory");
	} else {
		do {
			__asm__ __volatile__(
			"	ll	%1, %3	# arch_write_trylock	\n"
			"	li	%2, 0				\n"
			"	bnez	%1, 2f				\n"
			"	lui	%1, 0x8000			\n"
			"	sc	%1, %0				\n"
			"	li	%2, 1				\n"
			"2:						\n"
			: "=" GCC_OFF_SMALL_ASM() (rw->lock), "=&r" (tmp),
			  "=&r" (ret)
			: GCC_OFF_SMALL_ASM() (rw->lock)
			: "memory");
		} while (unlikely(!tmp));

		smp_llsc_mb();
	}

	return ret;
}

#define arch_read_lock_flags(lock, flags) arch_read_lock(lock)
#define arch_write_lock_flags(lock, flags) arch_write_lock(lock)

#define arch_spin_relax(lock)	cpu_relax()
#define arch_read_relax(lock)	cpu_relax()
#define arch_write_relax(lock)	cpu_relax()

#endif /* _ASM_SPINLOCK_H */