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>
diff --git a/arch/arm/mm/proc-v7.S b/arch/arm/mm/proc-v7.S
index 1f16f9e3..945f363 100644
--- a/arch/arm/mm/proc-v7.S
+++ b/arch/arm/mm/proc-v7.S
@@ -201,7 +201,7 @@
mrc p15, 0, r0, c0, c0, 0 @ read main ID register
and r10, r0, #0xff000000 @ ARM?
teq r10, #0x41000000
- bne 2f
+ bne 3f
and r5, r0, #0x00f00000 @ variant
and r6, r0, #0x0000000f @ revision
orr r6, r6, r5, lsr #20-4 @ combine variant and revision
@@ -231,8 +231,20 @@
orreq r10, r10, #(1 << 22) @ set the Write Allocate disable bit
mcreq p15, 1, r10, c9, c0, 2 @ write the L2 cache aux ctrl register
#endif
+ b 3f
-2: mov r10, #0
+ /* Cortex-A9 Errata */
+2: ldr r10, =0x00000c09 @ Cortex-A9 primary part number
+ teq r0, r10
+ bne 3f
+#ifdef CONFIG_ARM_ERRATA_742230
+ cmp r6, #0x22 @ only present up to r2p2
+ mrcle p15, 0, r10, c15, c0, 1 @ read diagnostic register
+ orrle r10, r10, #1 << 4 @ set bit #4
+ mcrle p15, 0, r10, c15, c0, 1 @ write diagnostic register
+#endif
+
+3: mov r10, #0
#ifdef HARVARD_CACHE
mcr p15, 0, r10, c7, c5, 0 @ I+BTB cache invalidate
#endif