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/* dmmu.c -- Data 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. */
 
/* DMMU model (not functional yet, currently just copy of data cache). */
 
#include "dmmu.h"
#include "abstract.h"
#include "stats.h"
#include "sprs.h"
#include "except.h"
 
extern int cont_run;
 
/* Data MMU */
 
unsigned long dmmu_translate(unsigned long virtaddr)
{
	unsigned long phyaddr = dmmu_simulate_tlb(virtaddr);
 
/*	printf("DMMU translate(%x) = %x\n", virtaddr, phyaddr);*/
	return phyaddr;
}
 
/* Number of DTLB sets used (power of 2, max is 256) */
#define DTLB_SETS 16
 
/* Entry size in bytes (8 == two singlewords) */
#define DTLB_ENTRY_SIZE 8
 
/* Number of DTLB ways (1, 2, 3 etc., max is 4). */
#define DTLB_WAYS 2
 
/* Number of usage states (2, 3, 4 etc., max is 4). */
#define DTLB_USTATES 2
 
void dtlb_info()
{
	if (!getsprbits(SPR_UPR, SPR_UPR_DMP)) {
		printf("DMMU not implemented. Set UPR[DMP].\n");
		return;
	}
 
	printf("Data MMU %dKB: ", DTLB_SETS * DTLB_ENTRY_SIZE * DTLB_WAYS / 1024);
	printf("%d ways, %d sets, entry size %d bytes\n", DTLB_WAYS, DTLB_SETS, DTLB_ENTRY_SIZE);
}
 
/* First check if virtual address is covered by DTLB and if it is:
    - increment DTLB read hit stats,
    - set 'lru' at this way to DTLB_USTATES - 1 and
      decrement 'lru' of other ways unless they have reached 0,
    - check page access attributes and invoke DMMU page fault exception
      handler if necessary
   and if not:
    - increment DTLB read miss stats
    - find lru way and entry and invoke DTLB miss exception handler
    - set 'lru' with DTLB_USTATES - 1 and decrement 'lru' of other
      ways unless they have reached 0
*/
 
void dtlb_status(int start_set)
{
	int set;
	int way;
	int end_set = DTLB_SETS;
 
	if (!getsprbits(SPR_UPR, SPR_UPR_DMP)) {
		printf("DMMU not implemented. Set UPR[DMP].\n");
		return;
	}
 
	if ((start_set >= 0) && (start_set < end_set))
		end_set = start_set + 1;
	else
		start_set = 0;
 
	printf("\nDMMU: ");
	/* Scan set(s) and way(s). */
	for (set = start_set; set < end_set; set++) {
		printf("\nSet %x: ", set);
		for (way = 0; way < DTLB_WAYS; way++) {
			printf("  way %d: ", way);
			printf("vpn=%x ", getsprbits(SPR_DTLBMR_BASE(way) + set, SPR_DTLBMR_VPN));
			printf("lru=%x ", getsprbits(SPR_DTLBMR_BASE(way) + set, SPR_DTLBMR_LRU));
			printf("pl1=%x ", getsprbits(SPR_DTLBMR_BASE(way) + set, SPR_DTLBMR_PL1));
			printf("v=%x ", getsprbits(SPR_DTLBMR_BASE(way) + set, SPR_DTLBMR_V));
 
			printf("a=%x ", getsprbits(SPR_DTLBTR_BASE(way) + set, SPR_DTLBTR_A));
			printf("d=%x ", getsprbits(SPR_DTLBTR_BASE(way) + set, SPR_DTLBTR_D));
			printf("ure=%x ", getsprbits(SPR_DTLBTR_BASE(way) + set, SPR_DTLBTR_URE));
			printf("uwe=%x ", getsprbits(SPR_DTLBTR_BASE(way) + set, SPR_DTLBTR_UWE));
			printf("sre=%x ", getsprbits(SPR_DTLBTR_BASE(way) + set, SPR_DTLBTR_SRE));
			printf("swe=%x ", getsprbits(SPR_DTLBTR_BASE(way) + set, SPR_DTLBTR_SWE));
			printf("ppn=%x ", getsprbits(SPR_DTLBTR_BASE(way) + set, SPR_DTLBTR_PPN));
		}
	}
	printf("\n");
}
 
unsigned long dmmu_simulate_tlb(unsigned long virtaddr)
{
	int set, way = -1;
	int i;
	unsigned long tagaddr;
	unsigned long vpn;
 
	if (!(mfspr(SPR_SR) & SPR_SR_DME) || (!getsprbits(SPR_SR, SPR_SR_DME)))
		return virtaddr;
 
	/* Which set to check out? */
	set = (virtaddr / PAGE_SIZE) % DTLB_SETS;
	tagaddr = (virtaddr / PAGE_SIZE) / DTLB_SETS;
	vpn = virtaddr / PAGE_SIZE;
 
	/* Scan all ways and try to find a matching way. */
	for (i = 0; i < DTLB_WAYS; i++)
		if ((getsprbits(SPR_DTLBMR_BASE(i) + set, SPR_DTLBMR_VPN) == vpn) &&
		    getsprbits(SPR_DTLBMR_BASE(i) + set, SPR_DTLBMR_V))
			way = i;
 
	/* Did we find our tlb entry? */
	if (way >= 0) { /* Yes, we did. */
		dmmu_stats.loads_tlbhit++;
		debug("DTLB hit (virtaddr=%x).\n", virtaddr);
 
		/* Set LRUs */
		for (i = 0; i < DTLB_WAYS; i++)
			if (getsprbits(SPR_DTLBMR_BASE(i) + set, SPR_DTLBMR_LRU))
				setsprbits(SPR_DTLBMR_BASE(i) + set, SPR_DTLBMR_LRU, getsprbits(SPR_DTLBMR_BASE(i) + set, SPR_DTLBMR_LRU) - 1);
		setsprbits(SPR_DTLBMR_BASE(way) + set, SPR_DTLBMR_LRU, DTLB_USTATES - 1);
 
		return getsprbits(SPR_DTLBTR_BASE(way) + set, SPR_DTLBTR_PPN) * PAGE_SIZE + (virtaddr % PAGE_SIZE);
	}
	else {	/* No, we didn't. */
		int minlru = DTLB_USTATES - 1;
		int minway = 0;
 
		dmmu_stats.loads_tlbmiss++;
#if 0
		for (i = 0; i < DTLB_WAYS; i++)
			if (getsprbits(SPR_DTLBMR_BASE(i) + set, SPR_DTLBMR_LRU) < minlru)
				minway = i;
 
		setsprbits(SPR_DTLBMR_BASE(minway) + set, SPR_DTLBMR_VPN, vpn);
		for (i = 0; i < DTLB_WAYS; i++)
			if (getsprbits(SPR_DTLBMR_BASE(i) + set, SPR_DTLBMR_LRU))
				setsprbits(SPR_DTLBMR_BASE(i) + set, SPR_DTLBMR_LRU, getsprbits(SPR_DTLBMR_BASE(i) + set, SPR_DTLBMR_LRU) - 1);
		setsprbits(SPR_DTLBMR_BASE(minway) + set, SPR_DTLBMR_LRU, DTLB_USTATES - 1);
		setsprbits(SPR_DTLBTR_BASE(minway) + set, SPR_DTLBTR_PPN, vpn); /* 1 to 1 */
		setsprbits(SPR_DTLBMR_BASE(minway) + set, SPR_DTLBMR_V, 1);
#endif
		except_handle(EXCEPT_DTLBMISS, virtaddr);
		/* if tlb refill implemented in HW */
		/* return getsprbits(SPR_DTLBTR_BASE(minway) + set, SPR_DTLBTR_PPN) * PAGE_SIZE + (virtaddr % PAGE_SIZE); */
		return 0;
	}
}