1/*
2 *  linux/arch/cris/mm/tlb.c
3 *
4 *  Copyright (C) 2000, 2001  Axis Communications AB
5 *
6 *  Authors:   Bjorn Wesen (bjornw@axis.com)
7 *
8 */
9
10#include <linux/init.h>
11#include <linux/kernel.h>
12#include <asm/tlb.h>
13
14#define D(x)
15
16/* The TLB can host up to 64 different mm contexts at the same time.
17 * The running context is R_MMU_CONTEXT, and each TLB entry contains a
18 * page_id that has to match to give a hit. In page_id_map, we keep track
19 * of which mm's we have assigned which page_id's, so that we know when
20 * to invalidate TLB entries.
21 *
22 * The last page_id is never running - it is used as an invalid page_id
23 * so we can make TLB entries that will never match.
24 *
25 * Notice that we need to make the flushes atomic, otherwise an interrupt
26 * handler that uses vmalloced memory might cause a TLB load in the middle
27 * of a flush causing.
28 */
29
30struct mm_struct *page_id_map[NUM_PAGEID];
31static int map_replace_ptr = 1;  /* which page_id_map entry to replace next */
32
33/* the following functions are similar to those used in the PPC port */
34
35static inline void
36alloc_context(struct mm_struct *mm)
37{
38	struct mm_struct *old_mm;
39
40	D(printk("tlb: alloc context %d (%p)\n", map_replace_ptr, mm));
41
42	/* did we replace an mm ? */
43
44	old_mm = page_id_map[map_replace_ptr];
45
46	if(old_mm) {
47		/* throw out any TLB entries belonging to the mm we replace
48		 * in the map
49		 */
50		flush_tlb_mm(old_mm);
51
52		old_mm->context.page_id = NO_CONTEXT;
53	}
54
55	/* insert it into the page_id_map */
56
57	mm->context.page_id = map_replace_ptr;
58	page_id_map[map_replace_ptr] = mm;
59
60	map_replace_ptr++;
61
62	if(map_replace_ptr == INVALID_PAGEID)
63		map_replace_ptr = 0;         /* wrap around */
64}
65
66/*
67 * if needed, get a new MMU context for the mm. otherwise nothing is done.
68 */
69
70void
71get_mmu_context(struct mm_struct *mm)
72{
73	if(mm->context.page_id == NO_CONTEXT)
74		alloc_context(mm);
75}
76
77/* called by __exit_mm to destroy the used MMU context if any before
78 * destroying the mm itself. this is only called when the last user of the mm
79 * drops it.
80 *
81 * the only thing we really need to do here is mark the used PID slot
82 * as empty.
83 */
84
85void
86destroy_context(struct mm_struct *mm)
87{
88	if(mm->context.page_id != NO_CONTEXT) {
89		D(printk("destroy_context %d (%p)\n", mm->context.page_id, mm));
90		flush_tlb_mm(mm);  /* TODO this might be redundant ? */
91		page_id_map[mm->context.page_id] = NULL;
92	}
93}
94
95/* called once during VM initialization, from init.c */
96
97void __init
98tlb_init(void)
99{
100	int i;
101
102	/* clear the page_id map */
103
104	for (i = 1; i < ARRAY_SIZE(page_id_map); i++)
105		page_id_map[i] = NULL;
106
107	/* invalidate the entire TLB */
108
109	flush_tlb_all();
110
111	/* the init_mm has context 0 from the boot */
112
113	page_id_map[0] = &init_mm;
114}
115