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authorScott Wood <scottwood@freescale.com>2007-06-25 14:50:41 -0500
committerKumar Gala <galak@kernel.crashing.org>2007-10-03 20:36:36 -0500
commit7401685242fbcbf4b0660726372c77a88c4af17d (patch)
tree71b814468d705c2c48184161c38a0295c832239d
parent663edbd2640447dc43840568cd5701e6c9878d63 (diff)
downloadop-kernel-dev-7401685242fbcbf4b0660726372c77a88c4af17d.zip
op-kernel-dev-7401685242fbcbf4b0660726372c77a88c4af17d.tar.gz
[POWERPC] 8xx: Work around CPU15 erratum.
The CPU15 erratum on MPC8xx chips can cause incorrect code execution under certain circumstances, where there is a conditional or indirect branch in the last word of a page, with a target in the last cache line of the next page. This patch implements one of the suggested workarounds, by forcing a TLB miss whenever execution crosses a page boundary. This is done by invalidating the pages before and after the one being loaded into the TLB in the ITLB miss handler. Signed-off-by: Scott Wood <scottwood@freescale.com> Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
-rw-r--r--arch/powerpc/kernel/head_8xx.S6
-rw-r--r--arch/powerpc/platforms/8xx/Kconfig16
2 files changed, 22 insertions, 0 deletions
diff --git a/arch/powerpc/kernel/head_8xx.S b/arch/powerpc/kernel/head_8xx.S
index 9c30938..f745839 100644
--- a/arch/powerpc/kernel/head_8xx.S
+++ b/arch/powerpc/kernel/head_8xx.S
@@ -298,6 +298,12 @@ InstructionTLBMiss:
stw r10, 0(r0)
stw r11, 4(r0)
mfspr r10, SPRN_SRR0 /* Get effective address of fault */
+#ifdef CONFIG_8xx_CPU15
+ addi r11, r10, 0x1000
+ tlbie r11
+ addi r11, r10, -0x1000
+ tlbie r11
+#endif
DO_8xx_CPU6(0x3780, r3)
mtspr SPRN_MD_EPN, r10 /* Have to use MD_EPN for walk, MI_EPN can't */
mfspr r10, SPRN_M_TWB /* Get level 1 table entry address */
diff --git a/arch/powerpc/platforms/8xx/Kconfig b/arch/powerpc/platforms/8xx/Kconfig
index 8ecd01a..322b155 100644
--- a/arch/powerpc/platforms/8xx/Kconfig
+++ b/arch/powerpc/platforms/8xx/Kconfig
@@ -100,6 +100,22 @@ config 8xx_CPU6
If in doubt, say N here.
+config 8xx_CPU15
+ bool "CPU15 Silicon Errata"
+ default y
+ help
+ This enables a workaround for erratum CPU15 on MPC8xx chips.
+ This bug can cause incorrect code execution under certain
+ circumstances. This workaround adds some overhead (a TLB miss
+ every time execution crosses a page boundary), and you may wish
+ to disable it if you have worked around the bug in the compiler
+ (by not placing conditional branches or branches to LR or CTR
+ in the last word of a page, with a target of the last cache
+ line in the next page), or if you have used some other
+ workaround.
+
+ If in doubt, say Y here.
+
choice
prompt "Microcode patch selection"
default NO_UCODE_PATCH
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