1/*
2 * MMU context handling.
3 *
4 * Copyright (C) 2011 Tobias Klauser <tklauser@distanz.ch>
5 * Copyright (C) 2009 Wind River Systems Inc
6 *   Implemented by fredrik.markstrom@gmail.com and ivarholmqvist@gmail.com
7 *
8 * This file is subject to the terms and conditions of the GNU General Public
9 * License.  See the file "COPYING" in the main directory of this archive
10 * for more details.
11 */
12
13#include <linux/mm.h>
14
15#include <asm/cpuinfo.h>
16#include <asm/mmu_context.h>
17#include <asm/tlb.h>
18
19/* The pids position and mask in context */
20#define PID_SHIFT	0
21#define PID_BITS	(cpuinfo.tlb_pid_num_bits)
22#define PID_MASK	((1UL << PID_BITS) - 1)
23
24/* The versions position and mask in context */
25#define VERSION_BITS	(32 - PID_BITS)
26#define VERSION_SHIFT	(PID_SHIFT + PID_BITS)
27#define VERSION_MASK	((1UL << VERSION_BITS) - 1)
28
29/* Return the version part of a context */
30#define CTX_VERSION(c)	(((c) >> VERSION_SHIFT) & VERSION_MASK)
31
32/* Return the pid part of a context */
33#define CTX_PID(c)	(((c) >> PID_SHIFT) & PID_MASK)
34
35/* Value of the first context (version 1, pid 0) */
36#define FIRST_CTX	((1UL << VERSION_SHIFT) | (0 << PID_SHIFT))
37
38static mm_context_t next_mmu_context;
39
40/*
41 * Initialize MMU context management stuff.
42 */
43void __init mmu_context_init(void)
44{
45	/* We need to set this here because the value depends on runtime data
46	 * from cpuinfo */
47	next_mmu_context = FIRST_CTX;
48}
49
50/*
51 * Set new context (pid), keep way
52 */
53static void set_context(mm_context_t context)
54{
55	set_mmu_pid(CTX_PID(context));
56}
57
58static mm_context_t get_new_context(void)
59{
60	/* Return the next pid */
61	next_mmu_context += (1UL << PID_SHIFT);
62
63	/* If the pid field wraps around we increase the version and
64	 * flush the tlb */
65	if (unlikely(CTX_PID(next_mmu_context) == 0)) {
66		/* Version is incremented since the pid increment above
67		 * overflows info version */
68		flush_cache_all();
69		flush_tlb_all();
70	}
71
72	/* If the version wraps we start over with the first generation, we do
73	 * not need to flush the tlb here since it's always done above */
74	if (unlikely(CTX_VERSION(next_mmu_context) == 0))
75		next_mmu_context = FIRST_CTX;
76
77	return next_mmu_context;
78}
79
80void switch_mm(struct mm_struct *prev, struct mm_struct *next,
81	       struct task_struct *tsk)
82{
83	unsigned long flags;
84
85	local_irq_save(flags);
86
87	/* If the process context we are swapping in has a different context
88	 * generation then we have it should get a new generation/pid */
89	if (unlikely(CTX_VERSION(next->context) !=
90		CTX_VERSION(next_mmu_context)))
91		next->context = get_new_context();
92
93	/* Save the current pgd so the fast tlb handler can find it */
94	pgd_current = next->pgd;
95
96	/* Set the current context */
97	set_context(next->context);
98
99	local_irq_restore(flags);
100}
101
102/*
103 * After we have set current->mm to a new value, this activates
104 * the context for the new mm so we see the new mappings.
105 */
106void activate_mm(struct mm_struct *prev, struct mm_struct *next)
107{
108	next->context = get_new_context();
109	set_context(next->context);
110	pgd_current = next->pgd;
111}
112
113unsigned long get_pid_from_context(mm_context_t *context)
114{
115	return CTX_PID((*context));
116}
117