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>

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 */

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)

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

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);
+}

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);
+}