Data written to the L2 cache can be overwritten with stale data on Cortex-A8

This patch is a workaround for the 460075 Cortex-A8 (r2p0) erratum. It
configures the L2 cache auxiliary control register so that the Write
Allocate mode for the L2 cache is disabled.
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

arch/arm/Kconfig

@@ -575,6 +575,17 @@ config ARM_ERRATA_458693
 	  different cache line. This false hazard might then cause a
 	  processor deadlock.
 
+config ARM_ERRATA_460075
+	bool "Data written to the L2 cache can be overwritten with stale data on Cortex-A8"
+	depends on CPU_V7
+	default n
+	help
+	  This option enables the workaround for the 458692 Cortex-A8
+	  (r2p0) erratum. Any asynchronous access to the L2 cache may
+	  encounter a situation in which recent store transactions to
+	  the L2 cache are lost and overwritten with stale memory
+	  contents from external memory.
+
 endmenu
 
 source "arch/arm/common/Kconfig"

arch/arm/mm/proc-v7.S

@@ -197,6 +197,11 @@ __v7_setup:
 	orr	r10, r10, #(1 << 5)		@ set L1NEON to 1
 	orr	r10, r10, #(1 << 9)		@ set PLDNOP to 1
 	mcr	p15, 0, r10, c1, c0, 1		@ write aux control register
+#endif
+#ifdef CONFIG_ARM_ERRATA_460075
+	mrc	p15, 1, r10, c9, c0, 2		@ read L2 cache aux ctrl register
+	orr	r10, r10, #(1 << 22)		@ set the Write Allocate disable bit
+	mcr	p15, 1, r10, c9, c0, 2		@ write the L2 cache aux ctrl register
 #endif
 	mov	r10, #0
 #ifdef HARVARD_CACHE