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/*
* MMU context handling.
*
* Copyright (C) 2011 Tobias Klauser <tklauser@distanz.ch>
* Copyright (C) 2009 Wind River Systems Inc
* Implemented by fredrik.markstrom@gmail.com and ivarholmqvist@gmail.com
*
* This file is subject to the terms and conditions of the GNU General Public
* License. See the file "COPYING" in the main directory of this archive
* for more details.
*/
#include <linux/mm.h>
#include <asm/cpuinfo.h>
#include <asm/mmu_context.h>
#include <asm/tlb.h>
/* The pids position and mask in context */
#define PID_SHIFT 0
#define PID_BITS (cpuinfo.tlb_pid_num_bits)
#define PID_MASK ((1UL << PID_BITS) - 1)
/* The versions position and mask in context */
#define VERSION_BITS (32 - PID_BITS)
#define VERSION_SHIFT (PID_SHIFT + PID_BITS)
#define VERSION_MASK ((1UL << VERSION_BITS) - 1)
/* Return the version part of a context */
#define CTX_VERSION(c) (((c) >> VERSION_SHIFT) & VERSION_MASK)
/* Return the pid part of a context */
#define CTX_PID(c) (((c) >> PID_SHIFT) & PID_MASK)
/* Value of the first context (version 1, pid 0) */
#define FIRST_CTX ((1UL << VERSION_SHIFT) | (0 << PID_SHIFT))
static mm_context_t next_mmu_context;
/*
* Initialize MMU context management stuff.
*/
void __init mmu_context_init(void)
{
/* We need to set this here because the value depends on runtime data
* from cpuinfo */
next_mmu_context = FIRST_CTX;
}
/*
* Set new context (pid), keep way
*/
static void set_context(mm_context_t context)
{
set_mmu_pid(CTX_PID(context));
}
static mm_context_t get_new_context(void)
{
/* Return the next pid */
next_mmu_context += (1UL << PID_SHIFT);
/* If the pid field wraps around we increase the version and
* flush the tlb */
if (unlikely(CTX_PID(next_mmu_context) == 0)) {
/* Version is incremented since the pid increment above
* overflows info version */
flush_cache_all();
flush_tlb_all();
}
/* If the version wraps we start over with the first generation, we do
* not need to flush the tlb here since it's always done above */
if (unlikely(CTX_VERSION(next_mmu_context) == 0))
next_mmu_context = FIRST_CTX;
return next_mmu_context;
}
void switch_mm(struct mm_struct *prev, struct mm_struct *next,
struct task_struct *tsk)
{
unsigned long flags;
local_irq_save(flags);
/* If the process context we are swapping in has a different context
* generation then we have it should get a new generation/pid */
if (unlikely(CTX_VERSION(next->context) !=
CTX_VERSION(next_mmu_context)))
next->context = get_new_context();
/* Save the current pgd so the fast tlb handler can find it */
pgd_current = next->pgd;
/* Set the current context */
set_context(next->context);
local_irq_restore(flags);
}
/*
* After we have set current->mm to a new value, this activates
* the context for the new mm so we see the new mappings.
*/
void activate_mm(struct mm_struct *prev, struct mm_struct *next)
{
next->context = get_new_context();
set_context(next->context);
pgd_current = next->pgd;
}
unsigned long get_pid_from_context(mm_context_t *context)
{
return CTX_PID((*context));
}
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