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>

1 files changed, 66 insertions, 0 deletions

diff --git a/arch/sh/mm/tlb-sh4.c b/arch/sh/mm/tlb-sh4.c
index 8cf550e2570..4c623474331 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);
+}