sh: Use MMU.TTB register as pointer to current pgd.

Add TTB accessor functions and give it a sensible default
value. We will use this later for optimizing the fault
path.

Signed-off-by: Stuart Menefy <stuart.menefy@st.com>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>

1 files changed, 8 insertions, 10 deletions

diff --git a/arch/sh/mm/init.c b/arch/sh/mm/init.c
index 8b275166f400..8c8d39118387 100644
--- a/arch/sh/mm/init.c
+++ b/arch/sh/mm/init.c
@@ -155,9 +155,6 @@ extern char __init_begin, __init_end;
 
 /*
  * paging_init() sets up the page tables
- *
- * This routines also unmaps the page at virtual kernel address 0, so
- * that we can trap those pesky NULL-reference errors in the kernel.
  */
 void __init paging_init(void)
 {
@@ -180,14 +177,11 @@ void __init paging_init(void)
          */
         {
                 unsigned long max_dma, low, start_pfn;
-                pgd_t *pg_dir;
-                int i;
-
-                /* We don't need kernel mapping as hardware support that. */
-                pg_dir = swapper_pg_dir;
 
-                for (i = 0; i < PTRS_PER_PGD; i++)
-                        pgd_val(pg_dir[i]) = 0;
+                /* We don't need to map the kernel through the TLB, as
+                 * it is permanatly mapped using P1. So clear the
+                 * entire pgd. */
+                memset(swapper_pg_dir, 0, sizeof(swapper_pg_dir));
 
                 /* Turn on the MMU */
                 enable_mmu();
@@ -206,6 +200,10 @@ void __init paging_init(void)
                 }
         }
 
+        /* Set an initial value for the MMU.TTB so we don't have to
+         * check for a null value. */
+        set_TTB(swapper_pg_dir);
+
 #elif defined(CONFIG_CPU_SH3) || defined(CONFIG_CPU_SH4)
         /*
          * If we don't have CONFIG_MMU set and the processor in question