m68k: ColdFire V4e MMU context support code

Add code to manage the context's of the ColdFire V4e MMU. This code is
mostly taken from the Freescale 2.6.35 kernel BSP for MMU enabled ColdFire.
Signed-off-by: Greg Ungerer <gerg@uclinux.org>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Matt Waddel <mwaddel@yahoo.com>
Acked-by: Kurt Mahan <kmahan@xmission.com>

arch/m68k/include/asm/atomic.h

@@ -55,6 +55,16 @@ static inline int atomic_dec_and_test(atomic_t *v)
 	return c != 0;
 }
 
+static inline int atomic_dec_and_test_lt(atomic_t *v)
+{
+	char c;
+	__asm__ __volatile__(
+		"subql #1,%1; slt %0"
+		: "=d" (c), "=m" (*v)
+		: "m" (*v));
+	return c != 0;
+}
+
 static inline int atomic_inc_and_test(atomic_t *v)
 {
 	char c;

arch/m68k/include/asm/mmu_context.h

@@ -8,7 +8,206 @@ static inline void enter_lazy_tlb(struct mm_struct *mm, struct task_struct *tsk)
 }
 
 #ifdef CONFIG_MMU
-#ifndef CONFIG_SUN3
+
+#if defined(CONFIG_COLDFIRE)
+
+#include <asm/atomic.h>
+#include <asm/bitops.h>
+#include <asm/mcfmmu.h>
+#include <asm/mmu.h>
+
+#define NO_CONTEXT		256
+#define LAST_CONTEXT		255
+#define FIRST_CONTEXT		1
+
+extern unsigned long context_map[];
+extern mm_context_t next_mmu_context;
+
+extern atomic_t nr_free_contexts;
+extern struct mm_struct *context_mm[LAST_CONTEXT+1];
+extern void steal_context(void);
+
+static inline void get_mmu_context(struct mm_struct *mm)
+{
+	mm_context_t ctx;
+
+	if (mm->context != NO_CONTEXT)
+		return;
+	while (atomic_dec_and_test_lt(&nr_free_contexts)) {
+		atomic_inc(&nr_free_contexts);
+		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 set_context(mm_context_t context, pgd_t *pgd)
+{
+	__asm__ __volatile__ ("movec %0,%%asid" : : "d" (context));
+}
+
+static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next,
+	struct task_struct *tsk)
+{
+	get_mmu_context(tsk->mm);
+	set_context(tsk->mm->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)
+{
+	get_mmu_context(mm);
+	set_context(mm->context, mm->pgd);
+}
+
+#define deactivate_mm(tsk, mm) do { } while (0)
+
+extern void mmu_context_init(void);
+#define prepare_arch_switch(next) load_ksp_mmu(next)
+
+static inline void load_ksp_mmu(struct task_struct *task)
+{
+	unsigned long flags;
+	struct mm_struct *mm;
+	int asid;
+	pgd_t *pgd;
+	pmd_t *pmd;
+	pte_t *pte;
+	unsigned long mmuar;
+
+	local_irq_save(flags);
+	mmuar = task->thread.ksp;
+
+	/* Search for a valid TLB entry, if one is found, don't remap */
+	mmu_write(MMUAR, mmuar);
+	mmu_write(MMUOR, MMUOR_STLB | MMUOR_ADR);
+	if (mmu_read(MMUSR) & MMUSR_HIT)
+		goto end;
+
+	if (mmuar >= PAGE_OFFSET) {
+		mm = &init_mm;
+	} else {
+		pr_info("load_ksp_mmu: non-kernel mm found: 0x%p\n", task->mm);
+		mm = task->mm;
+	}
+
+	if (!mm)
+		goto bug;
+
+	pgd = pgd_offset(mm, mmuar);
+	if (pgd_none(*pgd))
+		goto bug;
+
+	pmd = pmd_offset(pgd, mmuar);
+	if (pmd_none(*pmd))
+		goto bug;
+
+	pte = (mmuar >= PAGE_OFFSET) ? pte_offset_kernel(pmd, mmuar)
+				     : pte_offset_map(pmd, mmuar);
+	if (pte_none(*pte) || !pte_present(*pte))
+		goto bug;
+
+	set_pte(pte, pte_mkyoung(*pte));
+	asid = mm->context & 0xff;
+	if (!pte_dirty(*pte) && mmuar <= PAGE_OFFSET)
+		set_pte(pte, pte_wrprotect(*pte));
+
+	mmu_write(MMUTR, (mmuar & PAGE_MASK) | (asid << MMUTR_IDN) |
+		(((int)(pte->pte) & (int)CF_PAGE_MMUTR_MASK)
+		>> CF_PAGE_MMUTR_SHIFT) | MMUTR_V);
+
+	mmu_write(MMUDR, (pte_val(*pte) & PAGE_MASK) |
+		((pte->pte) & CF_PAGE_MMUDR_MASK) | MMUDR_SZ_8KB | MMUDR_X);
+
+	mmu_write(MMUOR, MMUOR_ACC | MMUOR_UAA);
+
+	goto end;
+
+bug:
+	pr_info("ksp load failed: mm=0x%p ksp=0x08%lx\n", mm, mmuar);
+end:
+	local_irq_restore(flags);
+}
+
+#elif defined(CONFIG_SUN3)
+#include <asm/sun3mmu.h>
+#include <linux/sched.h>
+
+extern unsigned long get_free_context(struct mm_struct *mm);
+extern void clear_context(unsigned long context);
+
+/* set the context for a new task to unmapped */
+static inline int init_new_context(struct task_struct *tsk,
+				   struct mm_struct *mm)
+{
+	mm->context = SUN3_INVALID_CONTEXT;
+	return 0;
+}
+
+/* find the context given to this process, and if it hasn't already
+   got one, go get one for it. */
+static inline void get_mmu_context(struct mm_struct *mm)
+{
+	if (mm->context == SUN3_INVALID_CONTEXT)
+		mm->context = get_free_context(mm);
+}
+
+/* flush context if allocated... */
+static inline void destroy_context(struct mm_struct *mm)
+{
+	if (mm->context != SUN3_INVALID_CONTEXT)
+		clear_context(mm->context);
+}
+
+static inline void activate_context(struct mm_struct *mm)
+{
+	get_mmu_context(mm);
+	sun3_put_context(mm->context);
+}
+
+static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next,
+			     struct task_struct *tsk)
+{
+	activate_context(tsk->mm);
+}
+
+#define deactivate_mm(tsk, mm)	do { } while (0)
+
+static inline void activate_mm(struct mm_struct *prev_mm,
+			       struct mm_struct *next_mm)
+{
+	activate_context(next_mm);
+}
+
+#else
 
 #include <asm/setup.h>
 #include <asm/page.h>
@@ -103,55 +302,8 @@ static inline void activate_mm(struct mm_struct *prev_mm,
 		switch_mm_0460(next_mm);
 }
 
-#else  /* CONFIG_SUN3 */
-#include <asm/sun3mmu.h>
-#include <linux/sched.h>
-
-extern unsigned long get_free_context(struct mm_struct *mm);
-extern void clear_context(unsigned long context);
-
-/* set the context for a new task to unmapped */
-static inline int init_new_context(struct task_struct *tsk, struct mm_struct *mm)
-{
-	mm->context = SUN3_INVALID_CONTEXT;
-	return 0;
-}
-
-/* find the context given to this process, and if it hasn't already
-   got one, go get one for it. */
-static inline void get_mmu_context(struct mm_struct *mm)
-{
-	if(mm->context == SUN3_INVALID_CONTEXT)
-		mm->context = get_free_context(mm);
-}
-
-/* flush context if allocated... */
-static inline void destroy_context(struct mm_struct *mm)
-{
-	if(mm->context != SUN3_INVALID_CONTEXT)
-		clear_context(mm->context);
-}
-
-static inline void activate_context(struct mm_struct *mm)
-{
-	get_mmu_context(mm);
-	sun3_put_context(mm->context);
-}
-
-static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next, struct task_struct *tsk)
-{
-	activate_context(tsk->mm);
-}
-
-#define deactivate_mm(tsk,mm)	do { } while (0)
-
-static inline void activate_mm(struct mm_struct *prev_mm,
-			       struct mm_struct *next_mm)
-{
-	activate_context(next_mm);
-}
-
 #endif
+
 #else /* !CONFIG_MMU */
 
 static inline int init_new_context(struct task_struct *tsk, struct mm_struct *mm)