text: /* SPDX-License-Identifier: GPL-2.0 */
  #ifndef __ASM_SPINLOCK_H
  #define __ASM_SPINLOCK_H
  
  #include <asm/barrier.h>
  #include <asm/ldcw.h>
  #include <asm/processor.h>
  #include <asm/spinlock_types.h>
  
  static inline int arch_spin_is_locked(arch_spinlock_t *x)
  {
  	volatile unsigned int *a = __ldcw_align(x);
  	return *a == 0;
  }
  
  #define arch_spin_lock(lock) arch_spin_lock_flags(lock, 0)
  
  static inline void arch_spin_lock_flags(arch_spinlock_t *x,
  					 unsigned long flags)
  {
  	volatile unsigned int *a;
  
  	a = __ldcw_align(x);
  	while (__ldcw(a) == 0)
  		while (*a == 0)
  			if (flags & PSW_SM_I) {
  				local_irq_enable();
  				cpu_relax();
  				local_irq_disable();
  			} else
  				cpu_relax();
  }
  
  static inline void arch_spin_unlock(arch_spinlock_t *x)
  {
  	volatile unsigned int *a;
  
  	a = __ldcw_align(x);
  	mb();
  	*a = 1;
  }
  
  static inline int arch_spin_trylock(arch_spinlock_t *x)
  {
  	volatile unsigned int *a;
  	int ret;
  
  	a = __ldcw_align(x);
          ret = __ldcw(a) != 0;
  
  	return ret;
  }
  
  /*
   * Read-write spinlocks, allowing multiple readers but only one writer.
   * Linux rwlocks are unfair to writers; they can be starved for an indefinite
   * time by readers.  With care, they can also be taken in interrupt context.
   *
   * In the PA-RISC implementation, we have a spinlock and a counter.
   * Readers use the lock to serialise their access to the counter (which
   * records how many readers currently hold the lock).
   * Writers hold the spinlock, preventing any readers or other writers from
   * grabbing the rwlock.
   */
  
  /* Note that we have to ensure interrupts are disabled in case we're
   * interrupted by some other code that wants to grab the same read lock */
  static  __inline__ void arch_read_lock(arch_rwlock_t *rw)
  {
  	unsigned long flags;
  	local_irq_save(flags);
  	arch_spin_lock_flags(&rw->lock, flags);
  	rw->counter++;
  	arch_spin_unlock(&rw->lock);
  	local_irq_restore(flags);
  }
  
  /* Note that we have to ensure interrupts are disabled in case we're
   * interrupted by some other code that wants to grab the same read lock */
  static  __inline__ void arch_read_unlock(arch_rwlock_t *rw)
  {
  	unsigned long flags;
  	local_irq_save(flags);
  	arch_spin_lock_flags(&rw->lock, flags);
  	rw->counter--;
  	arch_spin_unlock(&rw->lock);
  	local_irq_restore(flags);
  }
  
  /* Note that we have to ensure interrupts are disabled in case we're
   * interrupted by some other code that wants to grab the same read lock */
  static __inline__ int arch_read_trylock(arch_rwlock_t *rw)
  {
  	unsigned long flags;
   retry:
  	local_irq_save(flags);
  	if (arch_spin_trylock(&rw->lock)) {
  		rw->counter++;
  		arch_spin_unlock(&rw->lock);
  		local_irq_restore(flags);
  		return 1;
  	}
  
  	local_irq_restore(flags);
  	/* If write-locked, we fail to acquire the lock */
  	if (rw->counter < 0)
  		return 0;
  
  	/* Wait until we have a realistic chance at the lock */
  	while (arch_spin_is_locked(&rw->lock) && rw->counter >= 0)
  		cpu_relax();
  
  	goto retry;
  }
  
  /* Note that we have to ensure interrupts are disabled in case we're
   * interrupted by some other code that wants to read_trylock() this lock */
  static __inline__ void arch_write_lock(arch_rwlock_t *rw)
  {
  	unsigned long flags;
  retry:
  	local_irq_save(flags);
  	arch_spin_lock_flags(&rw->lock, flags);
  
  	if (rw->counter != 0) {
  		arch_spin_unlock(&rw->lock);
  		local_irq_restore(flags);
  
  		while (rw->counter != 0)
  			cpu_relax();
  
  		goto retry;
  	}
  
  	rw->counter = -1; /* mark as write-locked */
  	mb();
  	local_irq_restore(flags);
  }
  
  static __inline__ void arch_write_unlock(arch_rwlock_t *rw)
  {
  	rw->counter = 0;
  	arch_spin_unlock(&rw->lock);
  }
  
  /* Note that we have to ensure interrupts are disabled in case we're
   * interrupted by some other code that wants to read_trylock() this lock */
  static __inline__ int arch_write_trylock(arch_rwlock_t *rw)
  {
  	unsigned long flags;
  	int result = 0;
  
  	local_irq_save(flags);
  	if (arch_spin_trylock(&rw->lock)) {
  		if (rw->counter == 0) {
  			rw->counter = -1;
  			result = 1;
  		} else {
  			/* Read-locked.  Oh well. */
  			arch_spin_unlock(&rw->lock);
  		}
  	}
  	local_irq_restore(flags);
  
  	return result;
  }
  
  /*
   * read_can_lock - would read_trylock() succeed?
   * @lock: the rwlock in question.
   */
  static __inline__ int arch_read_can_lock(arch_rwlock_t *rw)
  {
  	return rw->counter >= 0;
  }
  
  /*
   * write_can_lock - would write_trylock() succeed?
   * @lock: the rwlock in question.
   */
  static __inline__ int arch_write_can_lock(arch_rwlock_t *rw)
  {
  	return !rw->counter;
  }
  
  #define arch_read_lock_flags(lock, flags) arch_read_lock(lock)
  #define arch_write_lock_flags(lock, flags) arch_write_lock(lock)
  
  #endif /* __ASM_SPINLOCK_H */
  