[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>

1 files changed, 16 insertions, 0 deletions

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