[PATCH 05/11] 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 <redacted>

---
 arch/powerpc/kernel/head_8xx.S | 22 ++++++++++------------
 1 file changed, 10 insertions(+), 12 deletions(-)

diff --git a/arch/powerpc/kernel/head_8xx.S b/arch/powerpc/kernel/head_8xx.S
index ae05f28..aa45225 100644
--- a/arch/powerpc/kernel/head_8xx.S
+++ b/arch/powerpc/kernel/head_8xx.S

@@ -322,13 +322,12 @@ InstructionTLBMiss:
 	mfspr	r11, SPRN_M_TW	/* Get level 1 table base address */
 #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 */

@@ -376,12 +375,11 @@ DataStoreTLBMiss:
 	andis.	r11, r10, 0x8000
 	mfspr	r11, SPRN_M_TW	/* Get level 1 table base address */
 	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.
 	 */

@@ -510,12 +508,11 @@ FixupDAR:/* Entry point for dcbx workaround. */
 	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
+	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

@@ -670,8 +667,7 @@ 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

@@ -850,6 +846,8 @@ _GLOBAL(set_context)
 	stw	r4, 0x4(r5)
 #endif
 
+	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

-- 
2.1.0

On Tue, 2014-12-16 at 16:03 +0100, Christophe Leroy wrote:

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.
=20
Signed-off-by: Christophe Leroy <redacted>

Nice :)
Acked-by: Joakim Tjernlund <redacted>

x.S

<< 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 */

<< 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 */

<< 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 */

is is

                * easier......until someone changes init's static structu=

res.

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Le 06/01/2015 13:08, David Laight a écrit :

quoted

On Tue, 2014-12-16 at 16:03 +0100, Christophe Leroy wrote:

quoted

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 <redacted>

Nice :)
Acked-by: Joakim Tjernlund <redacted>

quoted

---
  arch/powerpc/kernel/head_8xx.S | 22 ++++++++++------------
  1 file changed, 10 insertions(+), 12 deletions(-)

diff --git a/arch/powerpc/kernel/head_8xx.S b/arch/powerpc/kernel/head_8xx.S
index ae05f28..aa45225 100644
--- a/arch/powerpc/kernel/head_8xx.S
+++ b/arch/powerpc/kernel/head_8xx.S

@@ -322,13 +322,12 @@ InstructionTLBMiss:
         mfspr   r11, SPRN_M_TW/* Get level 1 table base address */
  #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 */

On the face of it that fragment doesn't look right when CONFIG_MODULES is undefined.

	David

I'm not sure I understand what you mean.

The other part of the patch adds the following:
+    li    r5, (swapper_pg_dir-PAGE_OFFSET)@l
+    sub    r4, r4, r5

r4 is the value put into SPRN_M_TW, so I don't see what may be wrong.

Christophe

From: leroy christophe

Le 06/01/2015 13:08, David Laight a =E9crit :

quoted

quoted

On Tue, 2014-12-16 at 16:03 +0100, Christophe Leroy wrote:

quoted

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 re=

move the

quoted

quoted

quoted

ori instruction.

Signed-off-by: Christophe Leroy <redacted>

Nice :)
Acked-by: Joakim Tjernlund <redacted>

quoted

---
  arch/powerpc/kernel/head_8xx.S | 22 ++++++++++------------
  1 file changed, 10 insertions(+), 12 deletions(-)

diff --git a/arch/powerpc/kernel/head_8xx.S b/arch/powerpc/kernel/hea=

d_8xx.S

quoted

quoted

quoted

index ae05f28..aa45225 100644

--- a/arch/powerpc/kernel/head_8xx.S
+++ b/arch/powerpc/kernel/head_8xx.S

@@ -322,13 +322,12 @@ InstructionTLBMiss:
         mfspr   r11, SPRN_M_TW/* Get level 1 table base address */
  #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

quoted

quoted

quoted

-       lwz     r11, 0(r11)/* Get the level 1 entry */
+       lwz     r11, (swapper_pg_dir-PAGE_OFFSET)@l(r11)/* Get the le=

vel 1 entry */

quoted

quoted

quoted

On the face of it that fragment doesn't look right when CONFIG_MODULES =

is undefined.

quoted

	David

I'm not sure I understand what you mean.
=20
The other part of the patch adds the following:
+    li    r5, (swapper_pg_dir-PAGE_OFFSET)@l
+    sub    r4, r4, r5
=20
r4 is the value put into SPRN_M_TW, so I don't see what may be wrong.

Ok, but it is completely non-obvious.
You probably need to change some comments somewhere about what is held
in SPRN_M_TW - since it is no longer the L1 base address, but that value
offset by some 'random' amount.

	David