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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 <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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