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 <da...@protonic.nl>
Signed-off-by: Kumar Gala <ga...@kernel.crashing.org>
---
* use SPRG4 instead of SPRG6 (6 was random, so use next free SPRG)
* init SPRG4 to 0 before we use it
arch/powerpc/include/asm/mmu.h | 6 ++++++
arch/powerpc/kernel/cputable.c | 9 ++++++---
arch/powerpc/kernel/head_32.S | 36 ++++++++++++++++++++++++++++++++----
3 files changed, 44 insertions(+), 7 deletions(-)
diff --git a/arch/powerpc/include/asm/mmu.h b/arch/powerpc/include/asm/mmu.h
index 10476a8..cbf1543 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/cputable.c b/arch/powerpc/kernel/cputable.c
index ccea243..cd1b687 100644
--- a/arch/powerpc/kernel/cputable.c
+++ b/arch/powerpc/kernel/cputable.c
@@ -1090,7 +1090,8 @@ 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,
@@ -1103,7 +1104,8 @@ 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,
@@ -1118,7 +1120,8 @@ 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 58dcc7c..1475ad5 100644
--- a/arch/powerpc/kernel/head_32.S
+++ b/arch/powerpc/kernel/head_32.S
@@ -153,6 +153,10 @@ __start:
*/
bl mmu_off
__after_mmu_off:
+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)
bl clear_bats
bl flush_tlbs
@@ -593,9 +597,21 @@ 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
@@ -661,9 +677,21 @@ 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
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