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/* immu.c -- Instruction MMU simulation

   Copyright (C) 1999 Damjan Lampret, lampret@opencores.org

This file is part of OpenRISC 1000 Architectural Simulator.

This program is free software; you can redistribute it and/or modify

it under the terms of the GNU General Public License as published by

the Free Software Foundation; either version 2 of the License, or

(at your option) any later version.

This program is distributed in the hope that it will be useful,

but WITHOUT ANY WARRANTY; without even the implied warranty of

MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

GNU General Public License for more details.

You should have received a copy of the GNU General Public License

along with this program; if not, write to the Free Software

Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */

/* IMMU model (not functional yet, currently just copy of data cache). */

#include "immu.h"

#include "abstract.h"

#include "stats.h"

#include "sprs.h"

#include "except.h"

extern int cont_run;

/* Insn MMU */

unsigned long immu_translate(unsigned long virtaddr)

{

        unsigned long phyaddr = immu_simulate_tlb(virtaddr);

/*      printf("IMMU translate(%x) = %x\n", virtaddr, phyaddr);*/

        return phyaddr;

}

/* Number of ITLB sets used (power of 2, max is 256) */

#define ITLB_SETS 16

/* Entry size in bytes (8 == two singlewords) */

#define ITLB_ENTRY_SIZE 8

/* Number of ITLB ways (1, 2, 3 etc., max is 4). */

#define ITLB_WAYS 2

/* Number of usage states (2, 3, 4 etc., max is 4). */

#define ITLB_USTATES 2

void itlb_info()

{

        printf("Insn MMU %dKB: ", ITLB_SETS * ITLB_ENTRY_SIZE * ITLB_WAYS / 1024);

        printf("%d ways, %d sets, entry size %d bytes\n", ITLB_WAYS, ITLB_SETS, ITLB_ENTRY_SIZE);

}

/* First check if virtual address is covered by ITLB and if it is:

    - increment ITLB read hit stats,

    - set 'lru' at this way to ITLB_USTATES - 1 and

      decrement 'lru' of other ways unless they have reached 0,

    - check page access attributes and invoke IMMU page fault exception

      handler if necessary

   and if not:

    - increment ITLB read miss stats

    - find lru way and entry and invoke ITLB miss exception handler

    - set 'lru' with ITLB_USTATES - 1 and decrement 'lru' of other

      ways unless they have reached 0

*/

unsigned long itlb_status(int start_set)

{

        int set;

        int way;

        int end_set = ITLB_SETS;

        if ((start_set >= 0) && (start_set < end_set))

                end_set = start_set + 1;

        else

                start_set = 0;

        printf("\nIMMU: ");

        /* Scan set(s) and way(s). */

        for (set = start_set; set < end_set; set++) {

                printf("\nSet %x: ", set);

                for (way = 0; way < ITLB_WAYS; way++) {

                        printf("  way %d: ", way);

                        printf("vpn=%x ", getsprbits(SPR_ITLBMR_BASE(way) + set, SPR_ITLBMR_VPN));

                        printf("lru=%x ", getsprbits(SPR_ITLBMR_BASE(way) + set, SPR_ITLBMR_LRU));

                        printf("pl1=%x ", getsprbits(SPR_ITLBMR_BASE(way) + set, SPR_ITLBMR_PL1));

                        printf("v=%x ", getsprbits(SPR_ITLBMR_BASE(way) + set, SPR_ITLBMR_V));

                        printf("a=%x ", getsprbits(SPR_ITLBTR_BASE(way) + set, SPR_ITLBTR_A));

                        printf("d=%x ", getsprbits(SPR_ITLBTR_BASE(way) + set, SPR_ITLBTR_D));

                        printf("ure=%x ", getsprbits(SPR_ITLBTR_BASE(way) + set, SPR_ITLBTR_URE));

                        printf("uwe=%x ", getsprbits(SPR_ITLBTR_BASE(way) + set, SPR_ITLBTR_UWE));

                        printf("sre=%x ", getsprbits(SPR_ITLBTR_BASE(way) + set, SPR_ITLBTR_SRE));

                        printf("swe=%x ", getsprbits(SPR_ITLBTR_BASE(way) + set, SPR_ITLBTR_SWE));

                        printf("ppn=%x ", getsprbits(SPR_ITLBTR_BASE(way) + set, SPR_ITLBTR_PPN));

                }

        }

        printf("\n");

}

unsigned long immu_simulate_tlb(unsigned long virtaddr)

{

        int set, way = -1;

        int i;

        unsigned long tagaddr;

        unsigned long vpn;

        if (! (mfspr(SPR_SR) & SPR_SR_IME))

                return virtaddr;

        /* Which set to check out? */

        set = (virtaddr / PAGE_SIZE) % ITLB_SETS;

        tagaddr = (virtaddr / PAGE_SIZE) / ITLB_SETS;

        vpn = virtaddr / PAGE_SIZE;

        /* Scan all ways and try to find a matching way. */

        for (i = 0; i < ITLB_WAYS; i++)

                if ((getsprbits(SPR_ITLBMR_BASE(i) + set, SPR_ITLBMR_VPN) == vpn) &&

                    getsprbits(SPR_ITLBMR_BASE(i) + set, SPR_ITLBMR_V))

                        way = i;

        /* Did we find our tlb entry? */

        if (way >= 0) { /* Yes, we did. */

                immu_stats.fetch_tlbhit++;

                debug("ITLB hit (virtaddr=%x).\n", virtaddr);

                /* Set LRUs */

                for (i = 0; i < ITLB_WAYS; i++)

                        if (getsprbits(SPR_ITLBMR_BASE(i) + set, SPR_ITLBMR_LRU))

                                setsprbits(SPR_ITLBMR_BASE(i) + set, SPR_ITLBMR_LRU, getsprbits(SPR_ITLBMR_BASE(i) + set, SPR_ITLBMR_LRU) - 1);

                setsprbits(SPR_ITLBMR_BASE(way) + set, SPR_ITLBMR_LRU, ITLB_USTATES - 1);

                return getsprbits(SPR_ITLBTR_BASE(way) + set, SPR_ITLBTR_PPN) * PAGE_SIZE + (virtaddr % PAGE_SIZE);

        }

        else {  /* No, we didn't. */

                int minlru = ITLB_USTATES - 1;

                int minway = 0;

                immu_stats.fetch_tlbmiss++;

                cont_run=0;

#if 0

                for (i = 0; i < ITLB_WAYS; i++)

                        if (getsprbits(SPR_ITLBMR_BASE(i) + set, SPR_ITLBMR_LRU) < minlru)

                                minway = i;

                setsprbits(SPR_ITLBMR_BASE(minway) + set, SPR_ITLBMR_VPN, vpn);

                for (i = 0; i < ITLB_WAYS; i++)

                        if (getsprbits(SPR_ITLBMR_BASE(i) + set, SPR_ITLBMR_LRU))

                                setsprbits(SPR_ITLBMR_BASE(i) + set, SPR_ITLBMR_LRU, getsprbits(SPR_ITLBMR_BASE(i) + set, SPR_ITLBMR_LRU) - 1);

                setsprbits(SPR_ITLBMR_BASE(minway) + set, SPR_ITLBMR_LRU, ITLB_USTATES - 1);

                setsprbits(SPR_ITLBTR_BASE(minway) + set, SPR_ITLBTR_PPN, vpn); /* 1 to 1 */

                setsprbits(SPR_ITLBMR_BASE(minway) + set, SPR_ITLBMR_V, 1);

#endif

                except_handle(EXCEPT_ITLBMISS, virtaddr);

                /* if tlb refill implemented in HW */

                /* return getsprbits(SPR_ITLBTR_BASE(minway) + set, SPR_ITLBTR_PPN) * PAGE_SIZE + (virtaddr % PAGE_SIZE); */

                return 0;

        }

}