linux/include/asm-m68k/system.h

#ifndef _M68K_SYSTEM_H
#define _M68K_SYSTEM_H

#include <linux/linkage.h>
#include <linux/kernel.h>
#include <asm/segment.h>
#include <asm/entry.h>

#ifdef __KERNEL__

/*
 * switch_to(n) should switch tasks to task ptr, first checking that
 * ptr isn't the current task, in which case it does nothing.  This
 * also clears the TS-flag if the task we switched to has used the
 * math co-processor latest.
 */
/*
 * switch_to() saves the extra registers, that are not saved
 * automatically by SAVE_SWITCH_STACK in resume(), ie. d0-d5 and
 * a0-a1. Some of these are used by schedule() and its predecessors
 * and so we might get see unexpected behaviors when a task returns
 * with unexpected register values.
 *
 * syscall stores these registers itself and none of them are used
 * by syscall after the function in the syscall has been called.
 *
 * Beware that resume now expects *next to be in d1 and the offset of
 * tss to be in a1. This saves a few instructions as we no longer have
 * to push them onto the stack and read them back right after.
 *
 * 02/17/96 - Jes Sorensen (jds@kom.auc.dk)
 *
 * Changed 96/09/19 by Andreas Schwab
 * pass prev in a0, next in a1
 */
asmlinkage void resume(void);
#define switch_to(prev,next,last) do { \
  register void *_prev __asm__ ("a0") = (prev); \
  register void *_next __asm__ ("a1") = (next); \
  register void *_last __asm__ ("d1"); \
  __asm__ __volatile__("jbsr resume" \
		       : "=a" (_prev), "=a" (_next), "=d" (_last) \
		       : "0" (_prev), "1" (_next) \
		       : "d0", "d2", "d3", "d4", "d5"); \
  (last) = _last; \
} while (0)


/* interrupt control.. */
#if 0
#define local_irq_enable() asm volatile ("andiw %0,%%sr": : "i" (ALLOWINT) : "memory")
#else
#include <linux/hardirq.h>
#define local_irq_enable() ({							\
	if (MACH_IS_Q40 || !hardirq_count())					\
		asm volatile ("andiw %0,%%sr": : "i" (ALLOWINT) : "memory");	\
})
#endif
#define local_irq_disable() asm volatile ("oriw  #0x0700,%%sr": : : "memory")
#define local_save_flags(x) asm volatile ("movew %%sr,%0":"=d" (x) : : "memory")
#define local_irq_restore(x) asm volatile ("movew %0,%%sr": :"d" (x) : "memory")

static inline int irqs_disabled(void)
{
	unsigned long flags;
	local_save_flags(flags);
	return flags & ~ALLOWINT;
}

/* For spinlocks etc */
#define local_irq_save(x)	({ local_save_flags(x); local_irq_disable(); })

/*
 * Force strict CPU ordering.
 * Not really required on m68k...
 */
#define nop()		do { asm volatile ("nop"); barrier(); } while (0)
#define mb()		barrier()
#define rmb()		barrier()
#define wmb()		barrier()
#define read_barrier_depends()	do { } while(0)
#define set_mb(var, value)    do { xchg(&var, value); } while (0)

#define smp_mb()	barrier()
#define smp_rmb()	barrier()
#define smp_wmb()	barrier()
#define smp_read_barrier_depends()	do { } while(0)


#define xchg(ptr,x) ((__typeof__(*(ptr)))__xchg((unsigned long)(x),(ptr),sizeof(*(ptr))))
#define tas(ptr) (xchg((ptr),1))

struct __xchg_dummy { unsigned long a[100]; };
#define __xg(x) ((volatile struct __xchg_dummy *)(x))

#ifndef CONFIG_RMW_INSNS
static inline unsigned long __xchg(unsigned long x, volatile void * ptr, int size)
{
	unsigned long flags, tmp;

	local_irq_save(flags);

	switch (size) {
	case 1:
		tmp = *(u8 *)ptr;
		*(u8 *)ptr = x;
		x = tmp;
		break;
	case 2:
		tmp = *(u16 *)ptr;
		*(u16 *)ptr = x;
		x = tmp;
		break;
	case 4:
		tmp = *(u32 *)ptr;
		*(u32 *)ptr = x;
		x = tmp;
		break;
	default:
		BUG();
	}

	local_irq_restore(flags);
	return x;
}
#else
static inline unsigned long __xchg(unsigned long x, volatile void * ptr, int size)
{
	switch (size) {
	    case 1:
		__asm__ __volatile__
			("moveb %2,%0\n\t"
			 "1:\n\t"
			 "casb %0,%1,%2\n\t"
			 "jne 1b"
			 : "=&d" (x) : "d" (x), "m" (*__xg(ptr)) : "memory");
		break;
	    case 2:
		__asm__ __volatile__
			("movew %2,%0\n\t"
			 "1:\n\t"
			 "casw %0,%1,%2\n\t"
			 "jne 1b"
			 : "=&d" (x) : "d" (x), "m" (*__xg(ptr)) : "memory");
		break;
	    case 4:
		__asm__ __volatile__
			("movel %2,%0\n\t"
			 "1:\n\t"
			 "casl %0,%1,%2\n\t"
			 "jne 1b"
			 : "=&d" (x) : "d" (x), "m" (*__xg(ptr)) : "memory");
		break;
	}
	return x;
}
#endif

/*
 * Atomic compare and exchange.  Compare OLD with MEM, if identical,
 * store NEW in MEM.  Return the initial value in MEM.  Success is
 * indicated by comparing RETURN with OLD.
 */
#ifdef CONFIG_RMW_INSNS
#define __HAVE_ARCH_CMPXCHG	1

static inline unsigned long __cmpxchg(volatile void *p, unsigned long old,
				      unsigned long new, int size)
{
	switch (size) {
	case 1:
		__asm__ __volatile__ ("casb %0,%2,%1"
				      : "=d" (old), "=m" (*(char *)p)
				      : "d" (new), "0" (old), "m" (*(char *)p));
		break;
	case 2:
		__asm__ __volatile__ ("casw %0,%2,%1"
				      : "=d" (old), "=m" (*(short *)p)
				      : "d" (new), "0" (old), "m" (*(short *)p));
		break;
	case 4:
		__asm__ __volatile__ ("casl %0,%2,%1"
				      : "=d" (old), "=m" (*(int *)p)
				      : "d" (new), "0" (old), "m" (*(int *)p));
		break;
	}
	return old;
}

#define cmpxchg(ptr,o,n)\
	((__typeof__(*(ptr)))__cmpxchg((ptr),(unsigned long)(o),\
					(unsigned long)(n),sizeof(*(ptr))))
#endif

#define arch_align_stack(x) (x)

#endif /* __KERNEL__ */

#endif /* _M68K_SYSTEM_H */