sh: New extended page flag to wire/unwire TLB entries

Provide a new extended page flag, _PAGE_WIRED and an SH4 implementation
for wiring TLB entries and use it in the fixmap code path so that we can
wire the fixmap TLB entry.

Signed-off-by: Matt Fleming <matt@console-pimps.org>

5 files changed, 156 insertions, 0 deletions

diff --git a/arch/sh/include/asm/pgtable_32.h b/arch/sh/include/asm/pgtable_32.h
index 5003ee86f67b..c573d45f1286 100644
--- a/arch/sh/include/asm/pgtable_32.h
+++ b/arch/sh/include/asm/pgtable_32.h
@@ -71,6 +71,8 @@
 #define _PAGE_EXT_KERN_WRITE    0x1000  /* EPR4-bit: Kernel space writable */
 #define _PAGE_EXT_KERN_READ     0x2000  /* EPR5-bit: Kernel space readable */
 
+#define _PAGE_EXT_WIRED         0x4000  /* software: Wire TLB entry */
+
 /* Wrapper for extended mode pgprot twiddling */
 #define _PAGE_EXT(x)            ((unsigned long long)(x) << 32)
 
@@ -164,6 +166,8 @@ static inline unsigned long copy_ptea_attributes(unsigned long x)
         (PTE_MASK | _PAGE_ACCESSED | _PAGE_CACHABLE | \
          _PAGE_DIRTY | _PAGE_SPECIAL)
 
+#define _PAGE_WIRED     (_PAGE_EXT(_PAGE_EXT_WIRED))
+
 #ifndef __ASSEMBLY__
 
 #if defined(CONFIG_X2TLB) /* SH-X2 TLB */
diff --git a/arch/sh/include/asm/tlb.h b/arch/sh/include/asm/tlb.h
index da8fe7ab8728..3ed2f7a05416 100644
--- a/arch/sh/include/asm/tlb.h
+++ b/arch/sh/include/asm/tlb.h
@@ -97,6 +97,22 @@ tlb_end_vma(struct mmu_gather *tlb, struct vm_area_struct *vma)
 
 #define tlb_migrate_finish(mm)          do { } while (0)
 
+#ifdef CONFIG_CPU_SH4
+extern void tlb_wire_entry(struct vm_area_struct *, unsigned long, pte_t);
+extern void tlb_unwire_entry(void);
+#else
+static inline void tlb_wire_entry(struct vm_area_struct *vma ,
+                                  unsigned long addr, pte_t pte)
+{
+        BUG();
+}
+
+static inline void tlb_unwire_entry(void)
+{
+        BUG();
+}
+#endif /* CONFIG_CPU_SH4 */
+
 #else /* CONFIG_MMU */
 
 #define tlb_start_vma(tlb, vma)                         do { } while (0)
diff --git a/arch/sh/include/cpu-sh4/cpu/mmu_context.h b/arch/sh/include/cpu-sh4/cpu/mmu_context.h
index 3ce7ef6c2978..03ea75c5315d 100644
--- a/arch/sh/include/cpu-sh4/cpu/mmu_context.h
+++ b/arch/sh/include/cpu-sh4/cpu/mmu_context.h
@@ -25,6 +25,10 @@
 
 #define MMUCR_TI                (1<<2)
 
+#define MMUCR_URB               0x00FC0000
+#define MMUCR_URB_SHIFT         18
+#define MMUCR_URB_NENTRIES      64
+
 #if defined(CONFIG_32BIT) && defined(CONFIG_CPU_SUBTYPE_ST40)
 #define MMUCR_SE                (1 << 4)
 #else
diff --git a/arch/sh/mm/tlb-pteaex.c b/arch/sh/mm/tlb-pteaex.c
index 409b7c2b4b9d..88c8bb05e16d 100644
--- a/arch/sh/mm/tlb-pteaex.c
+++ b/arch/sh/mm/tlb-pteaex.c
@@ -76,3 +76,69 @@ void __uses_jump_to_uncached local_flush_tlb_one(unsigned long asid,
         __raw_writel(asid, MMU_UTLB_ADDRESS_ARRAY2 | MMU_PAGE_ASSOC_BIT);
         back_to_cached();
 }
+
+/*
+ * Load the entry for 'addr' into the TLB and wire the entry.
+ */
+void tlb_wire_entry(struct vm_area_struct *vma, unsigned long addr, pte_t pte)
+{
+        unsigned long status, flags;
+        int urb;
+
+        local_irq_save(flags);
+
+        /* Load the entry into the TLB */
+        __update_tlb(vma, addr, pte);
+
+        /* ... and wire it up. */
+        status = ctrl_inl(MMUCR);
+        urb = (status & MMUCR_URB) >> MMUCR_URB_SHIFT;
+        status &= ~MMUCR_URB;
+
+        /*
+         * Make sure we're not trying to wire the last TLB entry slot.
+         */
+        BUG_ON(!--urb);
+
+        urb = urb % MMUCR_URB_NENTRIES;
+
+        status |= (urb << MMUCR_URB_SHIFT);
+        ctrl_outl(status, MMUCR);
+        ctrl_barrier();
+
+        local_irq_restore(flags);
+}
+
+/*
+ * Unwire the last wired TLB entry.
+ *
+ * It should also be noted that it is not possible to wire and unwire
+ * TLB entries in an arbitrary order. If you wire TLB entry N, followed
+ * by entry N+1, you must unwire entry N+1 first, then entry N. In this
+ * respect, it works like a stack or LIFO queue.
+ */
+void tlb_unwire_entry(void)
+{
+        unsigned long status, flags;
+        int urb;
+
+        local_irq_save(flags);
+
+        status = ctrl_inl(MMUCR);
+        urb = (status & MMUCR_URB) >> MMUCR_URB_SHIFT;
+        status &= ~MMUCR_URB;
+
+        /*
+         * Make sure we're not trying to unwire a TLB entry when none
+         * have been wired.
+         */
+        BUG_ON(urb++ == MMUCR_URB_NENTRIES);
+
+        urb = urb % MMUCR_URB_NENTRIES;
+
+        status |= (urb << MMUCR_URB_SHIFT);
+        ctrl_outl(status, MMUCR);
+        ctrl_barrier();
+
+        local_irq_restore(flags);
+}
diff --git a/arch/sh/mm/tlb-sh4.c b/arch/sh/mm/tlb-sh4.c
index 8cf550e2570f..4c6234743318 100644
--- a/arch/sh/mm/tlb-sh4.c
+++ b/arch/sh/mm/tlb-sh4.c
@@ -81,3 +81,69 @@ void __uses_jump_to_uncached local_flush_tlb_one(unsigned long asid,
         ctrl_outl(data, addr);
         back_to_cached();
 }
+
+/*
+ * Load the entry for 'addr' into the TLB and wire the entry.
+ */
+void tlb_wire_entry(struct vm_area_struct *vma, unsigned long addr, pte_t pte)
+{
+        unsigned long status, flags;
+        int urb;
+
+        local_irq_save(flags);
+
+        /* Load the entry into the TLB */
+        __update_tlb(vma, addr, pte);
+
+        /* ... and wire it up. */
+        status = ctrl_inl(MMUCR);
+        urb = (status & MMUCR_URB) >> MMUCR_URB_SHIFT;
+        status &= ~MMUCR_URB;
+
+        /*
+         * Make sure we're not trying to wire the last TLB entry slot.
+         */
+        BUG_ON(!--urb);
+
+        urb = urb % MMUCR_URB_NENTRIES;
+
+        status |= (urb << MMUCR_URB_SHIFT);
+        ctrl_outl(status, MMUCR);
+        ctrl_barrier();
+
+        local_irq_restore(flags);
+}
+
+/*
+ * Unwire the last wired TLB entry.
+ *
+ * It should also be noted that it is not possible to wire and unwire
+ * TLB entries in an arbitrary order. If you wire TLB entry N, followed
+ * by entry N+1, you must unwire entry N+1 first, then entry N. In this
+ * respect, it works like a stack or LIFO queue.
+ */
+void tlb_unwire_entry(void)
+{
+        unsigned long status, flags;
+        int urb;
+
+        local_irq_save(flags);
+
+        status = ctrl_inl(MMUCR);
+        urb = (status & MMUCR_URB) >> MMUCR_URB_SHIFT;
+        status &= ~MMUCR_URB;
+
+        /*
+         * Make sure we're not trying to unwire a TLB entry when none
+         * have been wired.
+         */
+        BUG_ON(urb++ == MMUCR_URB_NENTRIES);
+
+        urb = urb % MMUCR_URB_NENTRIES;
+
+        status |= (urb << MMUCR_URB_SHIFT);
+        ctrl_outl(status, MMUCR);
+        ctrl_barrier();
+
+        local_irq_restore(flags);
+}