ARM: 6388/1: errata: DMB operation may be faulty

On versions of the Cortex-A9 up to and including r2p2, under rare
circumstances, a DMB instruction between 2 write operations may not
ensure the correct visibility ordering of the 2 writes.

This workaround sets a bit in the diagnostic register of the Cortex-A9,
causing the DMB instruction to behave like a DSB, which functions
correctly on the affected cores.

Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

1 files changed, 12 insertions, 0 deletions

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 553b7cf17bfb..ab14c0a5d21e 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -1051,6 +1051,18 @@ config ARM_ERRATA_460075
           ACTLR register. Note that setting specific bits in the ACTLR register
           may not be available in non-secure mode.
 
+config ARM_ERRATA_742230
+        bool "ARM errata: DMB operation may be faulty"
+        depends on CPU_V7 && SMP
+        help
+          This option enables the workaround for the 742230 Cortex-A9
+          (r1p0..r2p2) erratum. Under rare circumstances, a DMB instruction
+          between two write operations may not ensure the correct visibility
+          ordering of the two writes. This workaround sets a specific bit in
+          the diagnostic register of the Cortex-A9 which causes the DMB
+          instruction to behave as a DSB, ensuring the correct behaviour of
+          the two writes.
+
 config PL310_ERRATA_588369
         bool "Clean & Invalidate maintenance operations do not invalidate clean lines"
         depends on CACHE_L2X0 && ARCH_OMAP4