/* SPDX-License-Identifier: GPL-2.0-or-later */
#ifndef _ASM_POWERPC_SIMPLE_SPINLOCK_H
#define _ASM_POWERPC_SIMPLE_SPINLOCK_H
/*
* Simple spin lock operations.
*
* Copyright (C) 2001-2004 Paul Mackerras <paulus@au.ibm.com>, IBM
* Copyright (C) 2001 Anton Blanchard <anton@au.ibm.com>, IBM
* Copyright (C) 2002 Dave Engebretsen <engebret@us.ibm.com>, IBM
* Rework to support virtual processors
*
* Type of int is used as a full 64b word is not necessary.
*
* (the type definitions are in asm/simple_spinlock_types.h)
*/
#include <linux/irqflags.h>
#include <linux/kcsan-checks.h>
#include <asm/paravirt.h>
#include <asm/paca.h>
#include <asm/synch.h>
#include <asm/ppc-opcode.h>
#ifdef CONFIG_PPC64
/* use 0x800000yy when locked, where yy == CPU number */
#ifdef __BIG_ENDIAN__
#define LOCK_TOKEN (*(u32 *)(&get_paca()->lock_token))
#else
#define LOCK_TOKEN (*(u32 *)(&get_paca()->paca_index))
#endif
#else
#define LOCK_TOKEN 1
#endif
static __always_inline int arch_spin_value_unlocked(arch_spinlock_t lock)
{
return lock.slock == 0;
}
static inline int arch_spin_is_locked(arch_spinlock_t *lock)
{
return !arch_spin_value_unlocked(READ_ONCE(*lock));
}
/*
* This returns the old value in the lock, so we succeeded
* in getting the lock if the return value is 0.
*/
static inline unsigned long __arch_spin_trylock(arch_spinlock_t *lock)
{
unsigned long tmp, token;
unsigned int eh = IS_ENABLED(CONFIG_PPC64);
token = LOCK_TOKEN;
__asm__ __volatile__(
"1: lwarx %0,0,%2,%[eh]\n\
cmpwi 0,%0,0\n\
bne- 2f\n\
stwcx. %1,0,%2\n\
bne- 1b\n"
PPC_ACQUIRE_BARRIER
"2:"
: "=&r" (tmp)
: "r" (token), "r" (&lock->slock), [eh] "n" (eh)
: "cr0", "memory");
return tmp;
}
static inline int arch_spin_trylock(arch_spinlock_t *lock)
{
return __arch_spin_trylock(lock) == 0;
}
/*
* On a system with shared processors (that is, where a physical
* processor is multiplexed between several virtual processors),
* there is no point spinning on a lock if the holder of the lock
* isn't currently scheduled on a physical processor. Instead
* we detect this situation and ask the hypervisor to give the
* rest of our timeslice to the lock holder.
*
* So that we can tell which virtual processor is holding a lock,
* we put 0x80000000 | smp_processor_id() in the lock when it is
* held. Conveniently, we have a word in the paca that holds this
* value.
*/
#if defined(CONFIG_PPC_SPLPAR)
/* We only yield to the hypervisor if we are in shared processor mode */
void splpar_spin_yield(arch_spinlock_t *lock);
void splpar_rw_yield(arch_rwlock_t *lock);
#else /* SPLPAR */
static inline void splpar_spin_yield(arch_spinlock_t *lock) {}
static inline void splpar_rw_yield(arch_rwlock_t *lock) {}
#endif
static inline void spin_yield(arch_spinlock_t *lock)
{
if (is_shared_processor())
splpar_spin_yield(lock);
else
barrier();
}
static inline void rw_yield(arch_rwlock_t *lock)
{
if (is_shared_processor())
splpar_rw_yield(lock);
else
barrier();
}
static inline void arch_spin_lock(arch_spinlock_t *lock)
{
while (1) {
if (likely(__arch_spin_trylock(lock) == 0))
break;
do {
HMT_low();
if (is_shared_processor())
splpar_spin_yield(lock);
} while (unlikely(lock->slock != 0));
HMT_medium();
}
}
static inline void arch_spin_unlock(arch_spinlock_t *lock)
{
kcsan_mb();
__asm__ __volatile__("# arch_spin_unlock\n\t"
PPC_RELEASE_BARRIER: : :"memory");
lock->slock = 0;
}
/*
* 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.
*/
#ifdef CONFIG_PPC64
#define __DO_SIGN_EXTEND "extsw %0,%0\n"
#define WRLOCK_TOKEN LOCK_TOKEN /* it's negative */
#else
#define __DO_SIGN_EXTEND
#define WRLOCK_TOKEN (-1)
#endif
/*
* This returns the old value in the lock + 1,
* so we got a read lock if the return value is > 0.
*/
static inline long __arch_read_trylock(arch_rwlock_t *rw)
{
long tmp;
unsigned int eh = IS_ENABLED(CONFIG_PPC64);
__asm__ __volatile__(
"1: lwarx %0,0,%1,%[eh]\n"
__DO_SIGN_EXTEND
" addic. %0,%0,1\n\
ble- 2f\n"
" stwcx. %0,0,%1\n\
bne- 1b\n"
PPC_ACQUIRE_BARRIER
"2:" : "=&r" (tmp)
: "r" (&rw->lock), [eh] "n" (eh)
: "cr0", "xer", "memory");
return tmp;
}
/*
* This returns the old value in the lock,
* so we got the write lock if the return value is 0.
*/
static inline long __arch_write_trylock(arch_rwlock_t *rw)
{
long tmp, token;
unsigned int eh = IS_ENABLED(CONFIG_PPC64);
token = WRLOCK_TOKEN;
__asm__ __volatile__(
"1: lwarx %0,0,%2,%[eh]\n\
cmpwi 0,%0,0\n\
bne- 2f\n"
" stwcx. %1,0,%2\n\
bne- 1b\n"
PPC_ACQUIRE_BARRIER
"2:" : "=&r" (tmp)
: "r" (token), "r" (&rw->lock), [eh] "n" (eh)
: "cr0", "memory");
return tmp;
}
static inline void arch_read_lock(arch_rwlock_t *rw)
{
while (1) {
if (likely(__arch_read_trylock(rw) > 0))
break;
do {
HMT_low();
if (is_shared_processor())
splpar_rw_yield(rw);
} while (unlikely(rw->lock < 0));
HMT_medium();
}
}
static inline void arch_write_lock(arch_rwlock_t *rw)
{
while (1) {
if (likely(__arch_write_trylock(rw) == 0))
break;
do {
HMT_low();
if (is_shared_processor())
splpar_rw_yield(rw);
} while (unlikely(rw->lock != 0));
HMT_medium();
}
}
static inline int arch_read_trylock(arch_rwlock_t *rw)
{
return __arch_read_trylock(rw) > 0;
}
static inline int arch_write_trylock(arch_rwlock_t *rw)
{
return __arch_write_trylock(rw) == 0;
}
static inline void arch_read_unlock(arch_rwlock_t *rw)
{
long tmp;
__asm__ __volatile__(
"# read_unlock\n\t"
PPC_RELEASE_BARRIER
"1: lwarx %0,0,%1\n\
addic %0,%0,-1\n"
" stwcx. %0,0,%1\n\
bne- 1b"
: "=&r"(tmp)
: "r"(&rw->lock)
: "cr0", "xer", "memory");
}
static inline void arch_write_unlock(arch_rwlock_t *rw)
{
__asm__ __volatile__("# write_unlock\n\t"
PPC_RELEASE_BARRIER: : :"memory");
rw->lock = 0;
}
#define arch_spin_relax(lock) spin_yield(lock)
#define arch_read_relax(lock) rw_yield(lock)
#define arch_write_relax(lock) rw_yield(lock)
#endif /* _ASM_POWERPC_SIMPLE_SPINLOCK_H */