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>

2 files changed, 132 insertions, 0 deletions

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);
+}