powerpc/8xx: Optimise access to swapper_pg_dir

All accessed to PGD entries are done via 0(r11).
By using lower part of swapper_pg_dir as load index to r11, we can remove the
ori instruction.

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Scott Wood <scottwood@freescale.com>

diff --git a/arch/powerpc/kernel/head_8xx.S b/arch/powerpc/kernel/head_8xx.S
index 0ab16b6..24934e7 100644 (file)
--- a/arch/powerpc/kernel/head_8xx.S
+++ b/arch/powerpc/kernel/head_8xx.S
@@ -319,16 +319,15 @@ InstructionTLBMiss:
         * pin the first 8MB of kernel memory */
        andis.  r11, r10, 0x8000        /* Address >= 0x80000000 */
 #endif
-       mfspr   r11, SPRN_M_TW  /* Get level 1 table base address */
+       mfspr   r11, SPRN_M_TW  /* Get level 1 table */
 #ifdef CONFIG_MODULES
        beq     3f
-       lis     r11, (swapper_pg_dir-PAGE_OFFSET)@h
-       ori     r11, r11, (swapper_pg_dir-PAGE_OFFSET)@l
+       lis     r11, (swapper_pg_dir-PAGE_OFFSET)@ha
 3:
 #endif
        /* Insert level 1 index */
        rlwimi  r11, r10, 32 - ((PAGE_SHIFT - 2) << 1), (PAGE_SHIFT - 2) << 1, 29
-       lwz     r11, 0(r11)     /* Get the level 1 entry */
+       lwz     r11, (swapper_pg_dir-PAGE_OFFSET)@l(r11)        /* Get the level 1 entry */
 
        /* Load the MI_TWC with the attributes for this "segment." */
        MTSPR_CPU6(SPRN_MI_TWC, r11, r3)        /* Set segment attributes */
@@ -374,14 +373,13 @@ DataStoreTLBMiss:
         * kernel page tables.
         */
        andis.  r11, r10, 0x8000
-       mfspr   r11, SPRN_M_TW  /* Get level 1 table base address */
+       mfspr   r11, SPRN_M_TW  /* Get level 1 table */
        beq     3f
-       lis     r11, (swapper_pg_dir-PAGE_OFFSET)@h
-       ori     r11, r11, (swapper_pg_dir-PAGE_OFFSET)@l
+       lis     r11, (swapper_pg_dir-PAGE_OFFSET)@ha
 3:
        /* Insert level 1 index */
        rlwimi  r11, r10, 32 - ((PAGE_SHIFT - 2) << 1), (PAGE_SHIFT - 2) << 1, 29
-       lwz     r11, 0(r11)     /* Get the level 1 entry */
+       lwz     r11, (swapper_pg_dir-PAGE_OFFSET)@l(r11)        /* Get the level 1 entry */
 
        /* We have a pte table, so load fetch the pte from the table.
         */
@@ -506,13 +504,12 @@ FixupDAR:/* Entry point for dcbx workaround. */
        /* fetch instruction from memory. */
        mfspr   r10, SPRN_SRR0
        andis.  r11, r10, 0x8000        /* Address >= 0x80000000 */
-       mfspr   r11, SPRN_M_TW  /* Get level 1 table base address */
-       beq-    3f              /* Branch if user space */
-       lis     r11, (swapper_pg_dir-PAGE_OFFSET)@h
-       ori     r11, r11, (swapper_pg_dir-PAGE_OFFSET)@l
+       mfspr   r11, SPRN_M_TW  /* Get level 1 table */
+       beq     3f
+       lis     r11, (swapper_pg_dir-PAGE_OFFSET)@ha
        /* Insert level 1 index */
 3:     rlwimi  r11, r10, 32 - ((PAGE_SHIFT - 2) << 1), (PAGE_SHIFT - 2) << 1, 29
-       lwz     r11, 0(r11)     /* Get the level 1 entry */
+       lwz     r11, (swapper_pg_dir-PAGE_OFFSET)@l(r11)        /* Get the level 1 entry */
        rlwinm  r11, r11,0,0,19 /* Extract page descriptor page address */
        /* Insert level 2 index */
        rlwimi  r11, r10, 32 - (PAGE_SHIFT - 2), 32 - PAGE_SHIFT, 29
@@ -667,8 +664,7 @@ start_here:
         * init's THREAD like the context switch code does, but this is
         * easier......until someone changes init's static structures.
         */
-       lis     r6, swapper_pg_dir@h
-       ori     r6, r6, swapper_pg_dir@l
+       lis     r6, swapper_pg_dir@ha
        tophys(r6,r6)
 #ifdef CONFIG_8xx_CPU6
        lis     r4, cpu6_errata_word@h
@@ -847,6 +843,13 @@ _GLOBAL(set_context)
        stw     r4, 0x4(r5)
 #endif
 
+       /* Register M_TW will contain base address of level 1 table minus the
+        * lower part of the kernel PGDIR base address, so that all accesses to
+        * level 1 table are done relative to lower part of kernel PGDIR base
+        * address.
+        */
+       li      r5, (swapper_pg_dir-PAGE_OFFSET)@l
+       sub     r4, r4, r5
 #ifdef CONFIG_8xx_CPU6
        lis     r6, cpu6_errata_word@h
        ori     r6, r6, cpu6_errata_word@l
@@ -854,7 +857,7 @@ _GLOBAL(set_context)
        li      r7, 0x3f80
        stw     r7, 12(r6)
        lwz     r7, 12(r6)
-        mtspr   SPRN_M_TW, r4               /* Update MMU base address */
+       mtspr   SPRN_M_TW, r4           /* Update pointeur to level 1 table */
        li      r7, 0x3380
        stw     r7, 12(r6)
        lwz     r7, 12(r6)