#ifndef __ALPHA_MMU_CONTEXT_H
#define __ALPHA_MMU_CONTEXT_H

/*
 * get a new mmu context..
 *
 * Copyright (C) 1996, Linus Torvalds
 */

#include <linux/config.h>
#include <asm/system.h>
#include <asm/machvec.h>

/*
 * The maximum ASN's the processor supports.  On the EV4 this is 63
 * but the PAL-code doesn't actually use this information.  On the
 * EV5 this is 127, and EV6 has 255.
 *
 * On the EV4, the ASNs are more-or-less useless anyway, as they are
 * only used as an icache tag, not for TB entries.  On the EV5 and EV6,
 * ASN's also validate the TB entries, and thus make a lot more sense.
 *
 * The EV4 ASN's don't even match the architecture manual, ugh.  And
 * I quote: "If a processor implements address space numbers (ASNs),
 * and the old PTE has the Address Space Match (ASM) bit clear (ASNs
 * in use) and the Valid bit set, then entries can also effectively be
 * made coherent by assigning a new, unused ASN to the currently
 * running process and not reusing the previous ASN before calling the
 * appropriate PALcode routine to invalidate the translation buffer
 * (TB)". 
 *
 * In short, the EV4 has a "kind of" ASN capability, but it doesn't actually
 * work correctly and can thus not be used (explaining the lack of PAL-code
 * support).
 */
#define EV4_MAX_ASN 63
#define EV5_MAX_ASN 127
#define EV6_MAX_ASN 255

#ifdef CONFIG_ALPHA_GENERIC
# define MAX_ASN	(alpha_mv.max_asn)
#else
# ifdef CONFIG_ALPHA_EV4
#  define MAX_ASN	EV4_MAX_ASN
# elif defined(CONFIG_ALPHA_EV5)
#  define MAX_ASN	EV5_MAX_ASN
# else
#  define MAX_ASN	EV6_MAX_ASN
# endif
#endif

#ifdef __SMP__
#define WIDTH_THIS_PROCESSOR	5
/*
 * last_asn[processor]:
 * 63                                            0
 * +-------------+----------------+--------------+
 * | asn version | this processor | hardware asn |
 * +-------------+----------------+--------------+
 */
extern unsigned long last_asn[];
#define asn_cache last_asn[p->processor]

#else
#define WIDTH_THIS_PROCESSOR	0
/*
 * asn_cache:
 * 63                                            0
 * +------------------------------+--------------+
 * |         asn version          | hardware asn |
 * +------------------------------+--------------+
 */
extern unsigned long asn_cache;
#endif /* __SMP__ */

#define WIDTH_HARDWARE_ASN	8
#define ASN_FIRST_VERSION (1UL << (WIDTH_THIS_PROCESSOR + WIDTH_HARDWARE_ASN))
#define HARDWARE_ASN_MASK ((1UL << WIDTH_HARDWARE_ASN) - 1)

/*
 * NOTE! The way this is set up, the high bits of the "asn_cache" (and
 * the "mm->context") are the ASN _version_ code. A version of 0 is
 * always considered invalid, so to invalidate another process you only
 * need to do "p->mm->context = 0".
 *
 * If we need more ASN's than the processor has, we invalidate the old
 * user TLB's (tbiap()) and start a new ASN version. That will automatically
 * force a new asn for any other processes the next time they want to
 * run.
 */

#ifndef __EXTERN_INLINE
#define __EXTERN_INLINE extern inline
#define __MMU_EXTERN_INLINE
#endif

extern void get_new_mmu_context(struct task_struct *p, struct mm_struct *mm);

__EXTERN_INLINE void ev4_get_mmu_context(struct task_struct *p)
{
	/* As described, ASN's are broken.  */
}

__EXTERN_INLINE void ev5_get_mmu_context(struct task_struct *p)
{
	struct mm_struct * mm = p->mm;

	if (mm) {
		unsigned long asn = asn_cache;
		/* Check if our ASN is of an older version,
		   or on a different CPU, and thus invalid.  */
		if ((mm->context ^ asn) & ~HARDWARE_ASN_MASK)
			get_new_mmu_context(p, mm);
	}
}

#ifdef CONFIG_ALPHA_GENERIC
# define get_mmu_context		(alpha_mv.mv_get_mmu_context)
#else
# ifdef CONFIG_ALPHA_EV4
#  define get_mmu_context		ev4_get_mmu_context
# else
#  define get_mmu_context		ev5_get_mmu_context
# endif
#endif

extern inline void init_new_context(struct mm_struct *mm)
{
	mm->context = 0;
}

extern inline void destroy_context(struct mm_struct *mm)
{
	/* Nothing to do.  */
}


/*
 * Force a context reload. This is needed when we change the page
 * table pointer or when we update the ASN of the current process.
 */

#if defined(CONFIG_ALPHA_GENERIC)
#define MASK_CONTEXT(tss) \
 ((struct thread_struct *)((unsigned long)(tss) & alpha_mv.mmu_context_mask))
#elif defined(CONFIG_ALPHA_DP264)
#define MASK_CONTEXT(tss) \
 ((struct thread_struct *)((unsigned long)(tss) & 0xfffffffffful))
#else
#define MASK_CONTEXT(tss)  (tss)
#endif

__EXTERN_INLINE struct thread_struct *
__reload_tss(struct thread_struct *tss)
{
	register struct thread_struct *a0 __asm__("$16");
	register struct thread_struct *v0 __asm__("$0");

	a0 = MASK_CONTEXT(tss);

	__asm__ __volatile__(
		"call_pal %2 #__reload_tss"
		: "=r"(v0), "=r"(a0)
		: "i"(PAL_swpctx), "r"(a0)
		: "$1", "$16", "$22", "$23", "$24", "$25");

	return v0;
}

__EXTERN_INLINE void
reload_context(struct task_struct *task)
{
	__reload_tss(&task->tss);
}

/*
 * After we have set current->mm to a new value, this activates the
 * context for the new mm so we see the new mappings.
 */

__EXTERN_INLINE void
activate_context(struct task_struct *task)
{
	get_mmu_context(task);
	reload_context(task);
}

#ifdef __MMU_EXTERN_INLINE
#undef __EXTERN_INLINE
#undef __MMU_EXTERN_INLINE
#endif

#endif /* __ALPHA_MMU_CONTEXT_H */
