Subject: [PATCH 3/3] powerpc/mm: e300c2/c3/c4 TLB errata workaround

From: Kumar Gala <[email-masked]>
Date: Thu, 19 Mar 2009 08:55:41 -0500

Complete workaround for DTLB errata in e300c2/c3/c4 processors.

Due to the bug, the hardware-implemented LRU algorythm always goes to way
1 of the TLB. This fix implements the proposed software workaround in
form of a LRW table for chosing the TLB-way.

Based on patch from David Jander <[email-masked]>

Signed-off-by: Kumar Gala <[email-masked]>
---
* Fix a linking problem that showed up in testing branch with not having
  #include <asm/mmu.h> in cpu_setup_6xx.S for the MMU feature fixup

 arch/powerpc/include/asm/mmu.h      |    6 ++++++
 arch/powerpc/kernel/cpu_setup_6xx.S |    5 +++++
 arch/powerpc/kernel/cputable.c      |    9 ++++++---
 arch/powerpc/kernel/head_32.S       |   32 ++++++++++++++++++++++++++++----
 4 files changed, 45 insertions(+), 7 deletions(-)

diff --git a/arch/powerpc/include/asm/mmu.h b/arch/powerpc/include/asm/mmu.h
index dc82dcd..c073de4 100644
--- a/arch/powerpc/include/asm/mmu.h
+++ b/arch/powerpc/include/asm/mmu.h
@@ -46,6 +46,12 @@
  */
 #define MMU_FTR_LOCK_BCAST_INVAL	ASM_CONST(0x00100000)
 
+/* This indicates that the processor doesn't handle way selection
+ * properly and needs SW to track and update the LRU state.  This
+ * is specific to an errata on e300c2/c3/c4 class parts
+ */
+#define MMU_FTR_NEED_DTLB_SW_LRU	ASM_CONST(0x00200000)
+
 #ifndef __ASSEMBLY__
 #include <asm/cputable.h>
 
diff --git a/arch/powerpc/kernel/cpu_setup_6xx.S b/arch/powerpc/kernel/cpu_setup_6xx.S
index 72d1d73..54f767e 100644
--- a/arch/powerpc/kernel/cpu_setup_6xx.S
+++ b/arch/powerpc/kernel/cpu_setup_6xx.S
@@ -15,9 +15,14 @@
 #include <asm/ppc_asm.h>
 #include <asm/asm-offsets.h>
 #include <asm/cache.h>
+#include <asm/mmu.h>
 
 _GLOBAL(__setup_cpu_603)
 	mflr	r4
+BEGIN_MMU_FTR_SECTION
+	li	r10,0
+	mtspr	SPRN_SPRG4,r10		/* init SW LRU tracking */
+END_MMU_FTR_SECTION_IFSET(MMU_FTR_NEED_DTLB_SW_LRU)
 BEGIN_FTR_SECTION
 	bl	__init_fpu_registers
 END_FTR_SECTION_IFCLR(CPU_FTR_FPU_UNAVAILABLE)
diff --git a/arch/powerpc/kernel/cputable.c b/arch/powerpc/kernel/cputable.c
index 6388386..4ec0a3a 100644
--- a/arch/powerpc/kernel/cputable.c
+++ b/arch/powerpc/kernel/cputable.c
@@ -1082,7 +1082,8 @@ static struct cpu_spec __initdata cpu_specs[] = {
 		.cpu_name		= "e300c2",
 		.cpu_features		= CPU_FTRS_E300C2,
 		.cpu_user_features	= PPC_FEATURE_32 | PPC_FEATURE_HAS_MMU,
-		.mmu_features		= MMU_FTR_USE_HIGH_BATS,
+		.mmu_features		= MMU_FTR_USE_HIGH_BATS |
+			MMU_FTR_NEED_DTLB_SW_LRU,
 		.icache_bsize		= 32,
 		.dcache_bsize		= 32,
 		.cpu_setup		= __setup_cpu_603,
@@ -1095,7 +1096,8 @@ static struct cpu_spec __initdata cpu_specs[] = {
 		.cpu_name		= "e300c3",
 		.cpu_features		= CPU_FTRS_E300,
 		.cpu_user_features	= COMMON_USER,
-		.mmu_features		= MMU_FTR_USE_HIGH_BATS,
+		.mmu_features		= MMU_FTR_USE_HIGH_BATS |
+			MMU_FTR_NEED_DTLB_SW_LRU,
 		.icache_bsize		= 32,
 		.dcache_bsize		= 32,
 		.cpu_setup		= __setup_cpu_603,
@@ -1110,7 +1112,8 @@ static struct cpu_spec __initdata cpu_specs[] = {
 		.cpu_name		= "e300c4",
 		.cpu_features		= CPU_FTRS_E300,
 		.cpu_user_features	= COMMON_USER,
-		.mmu_features		= MMU_FTR_USE_HIGH_BATS,
+		.mmu_features		= MMU_FTR_USE_HIGH_BATS |
+			MMU_FTR_NEED_DTLB_SW_LRU,
 		.icache_bsize		= 32,
 		.dcache_bsize		= 32,
 		.cpu_setup		= __setup_cpu_603,
diff --git a/arch/powerpc/kernel/head_32.S b/arch/powerpc/kernel/head_32.S
index 8a9dc79..6469ffa 100644
--- a/arch/powerpc/kernel/head_32.S
+++ b/arch/powerpc/kernel/head_32.S
@@ -590,9 +590,21 @@ BEGIN_FTR_SECTION
 	rlwinm	r1,r1,0,~_PAGE_COHERENT	/* clear M (coherence not required) */
 END_FTR_SECTION_IFCLR(CPU_FTR_NEED_COHERENT)
 	mtspr	SPRN_RPA,r1
+	mfspr	r2,SPRN_SRR1		/* Need to restore CR0 */
+	mtcrf	0x80,r2
+BEGIN_MMU_FTR_SECTION
+	li	r0,1
+	mfspr	r1,SPRN_SPRG4
+	rlwinm	r2,r3,20,27,31		/* Get Address bits 15:19 */
+	slw	r0,r0,r2
+	xor	r1,r0,r1
+	srw	r0,r1,r2
+	mtspr   SPRN_SPRG4,r1
+	mfspr	r2,SPRN_SRR1
+	rlwimi	r2,r0,31-14,14,14
+	mtspr   SPRN_SRR1,r2
+END_MMU_FTR_SECTION_IFSET(MMU_FTR_NEED_DTLB_SW_LRU)
 	tlbld	r3
-	mfspr	r3,SPRN_SRR1		/* Need to restore CR0 */
-	mtcrf	0x80,r3
 	rfi
 DataAddressInvalid:
 	mfspr	r3,SPRN_SRR1
@@ -658,9 +670,21 @@ BEGIN_FTR_SECTION
 	rlwinm	r1,r1,0,~_PAGE_COHERENT	/* clear M (coherence not required) */
 END_FTR_SECTION_IFCLR(CPU_FTR_NEED_COHERENT)
 	mtspr	SPRN_RPA,r1
+	mfspr	r2,SPRN_SRR1		/* Need to restore CR0 */
+	mtcrf	0x80,r2
+BEGIN_MMU_FTR_SECTION
+	li	r0,1
+	mfspr	r1,SPRN_SPRG4
+	rlwinm	r2,r3,20,27,31		/* Get Address bits 15:19 */
+	slw	r0,r0,r2
+	xor	r1,r0,r1
+	srw	r0,r1,r2
+	mtspr   SPRN_SPRG4,r1
+	mfspr	r2,SPRN_SRR1
+	rlwimi	r2,r0,31-14,14,14
+	mtspr   SPRN_SRR1,r2
+END_MMU_FTR_SECTION_IFSET(MMU_FTR_NEED_DTLB_SW_LRU)
 	tlbld	r3
-	mfspr	r3,SPRN_SRR1		/* Need to restore CR0 */
-	mtcrf	0x80,r3
 	rfi
 
 #ifndef CONFIG_ALTIVEC
-- 
1.5.6.6