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#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>

/*

 * 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.

 *

 * On the EV4, the ASNs are more-or-less useless anyway, as they are

 * only used as a icache tag, not for TB entries.  On the EV5 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).

 */

#ifdef CONFIG_ALPHA_EV5

#define MAX_ASN 127

#else

#define MAX_ASN 63

#define BROKEN_ASN 1

#endif

extern unsigned long asn_cache;

#define ASN_VERSION_SHIFT 16

#define ASN_VERSION_MASK ((~0UL) << ASN_VERSION_SHIFT)

#define ASN_FIRST_VERSION (1UL << ASN_VERSION_SHIFT)

extern inline void get_new_mmu_context(struct task_struct *p,

        struct mm_struct *mm,

        unsigned long asn)

{

        /* check if it's legal.. */

        if ((asn & ~ASN_VERSION_MASK) > MAX_ASN) {

                /* start a new version, invalidate all old asn's */

                tbiap(); imb();

                asn = (asn & ASN_VERSION_MASK) + ASN_FIRST_VERSION;

                if (!asn)

                        asn = ASN_FIRST_VERSION;

        }

        asn_cache = asn + 1;

        mm->context = asn;                      /* full version + asn */

        p->tss.asn = asn & ~ASN_VERSION_MASK;   /* just asn */

}

/*

 * 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.

 */

extern inline void get_mmu_context(struct task_struct *p)

{

#ifndef BROKEN_ASN

        struct mm_struct * mm = p->mm;

        if (mm) {

                unsigned long asn = asn_cache;

                /* Check if our ASN is of an older version and thus invalid */

                if ((mm->context ^ asn) & ASN_VERSION_MASK)

                        get_new_mmu_context(p, mm, asn);

        }

#endif

}

#endif