/* spinlock.h: 32-bit Sparc spinlock support.
*
* Copyright (C) 1997 David S. Miller ([email protected])
*/

#ifndef __SPARC_SPINLOCK_H
#define __SPARC_SPINLOCK_H

#ifndef __ASSEMBLY__

#include <asm/psr.h>
#include <asm/processor.h> /* for cpu_relax */

#define arch_spin_is_locked(lock) (*((volatile unsigned char *)(lock)) != 0)

#define arch_spin_unlock_wait(lock) \
do { while (arch_spin_is_locked(lock)) cpu_relax(); } while (0)

static inline void arch_spin_lock(arch_spinlock_t *lock)
{
__asm__ __volatile__(
"\n1:\n\t"
"ldstub [%0], %%g2\n\t"
"orcc %%g2, 0x0, %%g0\n\t"
"bne,a 2f\n\t"
" ldub [%0], %%g2\n\t"
".subsection 2\n"
"2:\n\t"
"orcc %%g2, 0x0, %%g0\n\t"
"bne,a 2b\n\t"
" ldub [%0], %%g2\n\t"
"b,a 1b\n\t"
".previous\n"
: /* no outputs */
: "r" (lock)
: "g2", "memory", "cc");
}

static inline int arch_spin_trylock(arch_spinlock_t *lock)
{
unsigned int result;
__asm__ __volatile__("ldstub [%1], %0"
: "=r" (result)
: "r" (lock)
: "memory");
return (result == 0);
}

static inline void arch_spin_unlock(arch_spinlock_t *lock)
{
__asm__ __volatile__("stb %%g0, [%0]" : : "r" (lock) : "memory");
}

/* 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.
*
* XXX This might create some problems with my dual spinlock
* XXX scheme, deadlocks etc. -DaveM
*
* Sort of like atomic_t's on Sparc, but even more clever.
*
* ------------------------------------
* | 24-bit counter | wlock | arch_rwlock_t
* ------------------------------------
* 31 8 7 0
*
* wlock signifies the one writer is in or somebody is updating
* counter. For a writer, if he successfully acquires the wlock,
* but counter is non-zero, he has to release the lock and wait,
* till both counter and wlock are zero.
*
* Unfortunately this scheme limits us to ~16,000,000 cpus.
*/
static inline void __arch_read_lock(arch_rwlock_t *rw)
{
register arch_rwlock_t *lp asm("g1");
lp = rw;
__asm__ __volatile__(
"mov %%o7, %%g4\n\t"
"call ___rw_read_enter\n\t"
" ldstub [%%g1 + 3], %%g2\n"
: /* no outputs */
: "r" (lp)
: "g2", "g4", "memory", "cc");
}

#define arch_read_lock(lock) \
do { unsigned long flags; \
local_irq_save(flags); \
__arch_read_lock(lock); \
local_irq_restore(flags); \
} while(0)

static inline void __arch_read_unlock(arch_rwlock_t *rw)
{
register arch_rwlock_t *lp asm("g1");
lp = rw;
__asm__ __volatile__(
"mov %%o7, %%g4\n\t"
"call ___rw_read_exit\n\t"
" ldstub [%%g1 + 3], %%g2\n"
: /* no outputs */
: "r" (lp)
: "g2", "g4", "memory", "cc");
}

#define arch_read_unlock(lock) \
do { unsigned long flags; \
local_irq_save(flags); \
__arch_read_unlock(lock); \
local_irq_restore(flags); \
} while(0)

static inline void arch_write_lock(arch_rwlock_t *rw)
{
register arch_rwlock_t *lp asm("g1");
lp = rw;
__asm__ __volatile__(
"mov %%o7, %%g4\n\t"
"call ___rw_write_enter\n\t"
" ldstub [%%g1 + 3], %%g2\n"
: /* no outputs */
: "r" (lp)
: "g2", "g4", "memory", "cc");
*(volatile __u32 *)&lp->lock = ~0U;
}

static void inline arch_write_unlock(arch_rwlock_t *lock)
{
__asm__ __volatile__(
" st %%g0, [%0]"
: /* no outputs */
: "r" (lock)
: "memory");
}

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

__asm__ __volatile__("ldstub [%1 + 3], %0"
: "=r" (val)
: "r" (&rw->lock)
: "memory");

if (val == 0) {
val = rw->lock & ~0xff;
if (val)
((volatile u8*)&rw->lock)[3] = 0;
else
*(volatile u32*)&rw->lock = ~0U;
}

return (val == 0);
}

static inline int __arch_read_trylock(arch_rwlock_t *rw)
{
register arch_rwlock_t *lp asm("g1");
register int res asm("o0");
lp = rw;
__asm__ __volatile__(
"mov %%o7, %%g4\n\t"
"call ___rw_read_try\n\t"
" ldstub [%%g1 + 3], %%g2\n"
: "=r" (res)
: "r" (lp)
: "g2", "g4", "memory", "cc");
return res;
}

#define arch_read_trylock(lock) \
({ unsigned long flags; \
int res; \
local_irq_save(flags); \
res = __arch_read_trylock(lock); \
local_irq_restore(flags); \
res; \
})

#define arch_spin_lock_flags(lock, flags) arch_spin_lock(lock)
#define arch_read_lock_flags(rw, flags) arch_read_lock(rw)
#define arch_write_lock_flags(rw, flags) arch_write_lock(rw)

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

#define arch_read_can_lock(rw) (!((rw)->lock & 0xff))
#define arch_write_can_lock(rw) (!(rw)->lock)

#endif /* !(__ASSEMBLY__) */

#endif /* __SPARC_SPINLOCK_H */