ARM: 8862/1: errata: 814220-B-Cache maintenance by set/way operations can execute out of order

The v7 ARM states that all cache and branch predictor maintenance operations
that do not specify an address execute, relative to each other, in program
order. However, because of this erratum, an L2 set/way cache maintenance
operation can overtake an L1 set/way cache maintenance operation, this would
cause the data corruption.

This ERRATA affected the Cortex-A7 and present in r0p2, r0p3, r0p4, r0p5.

This patch is the SW workaround by adding a DSB before changing cache levels as
the ARM ERRATA: ARM/MP: 814220 told in the ARM ERRATA documentation.
Signed-off-by: Jason Liu <r64343@freescale.com>
Signed-off-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>

arch/arm/Kconfig

@@ -1250,6 +1250,18 @@ config PCI_HOST_ITE8152
 	default y
 	select DMABOUNCE
 
+config ARM_ERRATA_814220
+	bool "ARM errata: Cache maintenance by set/way operations can execute out of order"
+	depends on CPU_V7
+	help
+	  The v7 ARM states that all cache and branch predictor maintenance
+	  operations that do not specify an address execute, relative to
+	  each other, in program order.
+	  However, because of this erratum, an L2 set/way cache maintenance
+	  operation can overtake an L1 set/way cache maintenance operation.
+	  This ERRATA only affected the Cortex-A7 and present in r0p2, r0p3,
+	  r0p4, r0p5.
+
 endmenu
 
 menu "Kernel Features"

arch/arm/mm/cache-v7.S

@@ -171,6 +171,9 @@ loop2:
 skip:
 	add	r10, r10, #2			@ increment cache number
 	cmp	r3, r10
+#ifdef CONFIG_ARM_ERRATA_814220
+	dsb
+#endif
 	bgt	flush_levels
 finished:
 	mov	r10, #0				@ switch back to cache level 0