ARM: 7541/1: Add ARM ERRATA 775420 workaround

arm: Add ARM ERRATA 775420 workaround

Workaround for the 775420 Cortex-A9 (r2p2, r2p6,r2p8,r2p10,r3p0) erratum.
In case a date cache maintenance operation aborts with MMU exception, it
might cause the processor to deadlock. This workaround puts DSB before
executing ISB if an abort may occur on cache maintenance.

Based on work by Kouei Abe and feedback from Catalin Marinas.
Signed-off-by: Kouei Abe <kouei.abe.cp@rms.renesas.com>
[ horms@verge.net.au: Changed to implementation
  suggested by catalin.marinas@arm.com ]
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Simon Horman <horms@verge.net.au>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/Kconfig

@@ -1413,6 +1413,16 @@ config PL310_ERRATA_769419
 	  on systems with an outer cache, the store buffer is drained
 	  explicitly.
 
+config ARM_ERRATA_775420
+       bool "ARM errata: A data cache maintenance operation which aborts, might lead to deadlock"
+       depends on CPU_V7
+       help
+	 This option enables the workaround for the 775420 Cortex-A9 (r2p2,
+	 r2p6,r2p8,r2p10,r3p0) erratum. In case a date cache maintenance
+	 operation aborts with MMU exception, it might cause the processor
+	 to deadlock. This workaround puts DSB before executing ISB if
+	 an abort may occur on cache maintenance.
+
 endmenu
 
 source "arch/arm/common/Kconfig"

arch/arm/mm/cache-v7.S

@@ -211,6 +211,9 @@ ENTRY(v7_coherent_user_range)
  * isn't mapped, fail with -EFAULT.
  */
 9001:
+#ifdef CONFIG_ARM_ERRATA_775420
+	dsb
+#endif
 	mov	r0, #-EFAULT
 	mov	pc, lr
  UNWIND(.fnend		)