ARM: 6416/1: errata: faulty hazard checking in the Store Buffer may lead to data corruption

On the r2p0, r2p1 and r2p2 versions of the Cortex-A9, data corruption
can occur under very rare conditions due to a store buffer optimisation.

This workaround sets a bit in the diagnostic register of the Cortex-A9,
disabling the optimisation and preventing the problem from occurring.

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>

2 files changed, 22 insertions, 0 deletions

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 88c97bc7a6f5..9c26ba7244fb 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -1101,6 +1101,20 @@ config ARM_ERRATA_720789
           invalidated are not, resulting in an incoherency in the system page
           tables. The workaround changes the TLB flushing routines to invalidate
           entries regardless of the ASID.
+
+config ARM_ERRATA_743622
+        bool "ARM errata: Faulty hazard checking in the Store Buffer may lead to data corruption"
+        depends on CPU_V7
+        help
+          This option enables the workaround for the 743622 Cortex-A9
+          (r2p0..r2p2) erratum. Under very rare conditions, a faulty
+          optimisation in the Cortex-A9 Store Buffer may lead to data
+          corruption. This workaround sets a specific bit in the diagnostic
+          register of the Cortex-A9 which disables the Store Buffer
+          optimisation, preventing the defect from occurring. This has no
+          visible impact on the overall performance or power consumption of the
+          processor.
+
 endmenu
 
 source "arch/arm/common/Kconfig"
diff --git a/arch/arm/mm/proc-v7.S b/arch/arm/mm/proc-v7.S
index 7563ff0141bd..75619c55f137 100644
--- a/arch/arm/mm/proc-v7.S
+++ b/arch/arm/mm/proc-v7.S
@@ -253,6 +253,14 @@ __v7_setup:
         orreq   r10, r10, #1 << 22              @ set bit #22
         mcreq   p15, 0, r10, c15, c0, 1         @ write diagnostic register
 #endif
+#ifdef CONFIG_ARM_ERRATA_743622
+        teq     r6, #0x20                       @ present in r2p0
+        teqne   r6, #0x21                       @ present in r2p1
+        teqne   r6, #0x22                       @ present in r2p2
+        mrceq   p15, 0, r10, c15, c0, 1         @ read diagnostic register
+        orreq   r10, r10, #1 << 6               @ set bit #6
+        mcreq   p15, 0, r10, c15, c0, 1         @ write diagnostic register
+#endif
 
 3:      mov     r10, #0
 #ifdef HARVARD_CACHE