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/*
* Copyright (C) 2008-2009 Michal Simek <monstr@monstr.eu>
* Copyright (C) 2008-2009 PetaLogix
* Copyright (C) 2006 Atmark Techno, Inc.
*
* 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.
*/
#ifndef _ASM_MICROBLAZE_MMU_CONTEXT_H
#define _ASM_MICROBLAZE_MMU_CONTEXT_H
#include <linux/atomic.h>
#include <linux/mm_types.h>
#include <asm/bitops.h>
#include <asm/mmu.h>
#include <asm-generic/mm_hooks.h>
# ifdef __KERNEL__
/*
* This function defines the mapping from contexts to VSIDs (virtual
* segment IDs). We use a skew on both the context and the high 4 bits
* of the 32-bit virtual address (the "effective segment ID") in order
* to spread out the entries in the MMU hash table.
*/
# define CTX_TO_VSID(ctx, va) (((ctx) * (897 * 16) + ((va) >> 28) * 0x111) \
& 0xffffff)
/*
MicroBlaze has 256 contexts, so we can just rotate through these
as a way of "switching" contexts. If the TID of the TLB is zero,
the PID/TID comparison is disabled, so we can use a TID of zero
to represent all kernel pages as shared among all contexts.
*/
static inline void enter_lazy_tlb(struct mm_struct *mm, struct task_struct *tsk)
{
}
# define NO_CONTEXT 256
# define LAST_CONTEXT 255
# define FIRST_CONTEXT 1
/*
* Set the current MMU context.
* This is done byloading up the segment registers for the user part of the
* address space.
*
* Since the PGD is immediately available, it is much faster to simply
* pass this along as a second parameter, which is required for 8xx and
* can be used for debugging on all processors (if you happen to have
* an Abatron).
*/
extern void set_context(mm_context_t context, pgd_t *pgd);
/*
* Bitmap of contexts in use.
* The size of this bitmap is LAST_CONTEXT + 1 bits.
*/
extern unsigned long context_map[];
/*
* This caches the next context number that we expect to be free.
* Its use is an optimization only, we can't rely on this context
* number to be free, but it usually will be.
*/
extern mm_context_t next_mmu_context;
/*
* Since we don't have sufficient contexts to give one to every task
* that could be in the system, we need to be able to steal contexts.
* These variables support that.
*/
extern atomic_t nr_free_contexts;
extern struct mm_struct *context_mm[LAST_CONTEXT+1];
extern void steal_context(void);
/*
* Get a new mmu context for the address space described by `mm'.
*/
static inline void get_mmu_context(struct mm_struct *mm)
{
mm_context_t ctx;
if (mm->context != NO_CONTEXT)
return;
while (atomic_dec_if_positive(&nr_free_contexts) < 0)
steal_context();
ctx = next_mmu_context;
while (test_and_set_bit(ctx, context_map)) {
ctx = find_next_zero_bit(context_map, LAST_CONTEXT+1, ctx);
if (ctx > LAST_CONTEXT)
ctx = 0;
}
next_mmu_context = (ctx + 1) & LAST_CONTEXT;
mm->context = ctx;
context_mm[ctx] = mm;
}
/*
* Set up the context for a new address space.
*/
# define init_new_context(tsk, mm) (((mm)->context = NO_CONTEXT), 0)
/*
* We're finished using the context for an address space.
*/
static inline void destroy_context(struct mm_struct *mm)
{
if (mm->context != NO_CONTEXT) {
clear_bit(mm->context, context_map);
mm->context = NO_CONTEXT;
atomic_inc(&nr_free_contexts);
}
}
static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next,
struct task_struct *tsk)
{
tsk->thread.pgdir = next->pgd;
get_mmu_context(next);
set_context(next->context, next->pgd);
}
/*
* After we have set current->mm to a new value, this activates
* the context for the new mm so we see the new mappings.
*/
static inline void activate_mm(struct mm_struct *active_mm,
struct mm_struct *mm)
{
current->thread.pgdir = mm->pgd;
get_mmu_context(mm);
set_context(mm->context, mm->pgd);
}
extern void mmu_context_init(void);
# endif /* __KERNEL__ */
#endif /* _ASM_MICROBLAZE_MMU_CONTEXT_H */
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