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/Kconfig b/arch/arm/Kconfig
index 553b7cf..ab14c0a 100644 (file)
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -1051,6 +1051,18 @@ config ARM_ERRATA_460075
          ACTLR register. Note that setting specific bits in the ACTLR register
          may not be available in non-secure mode.
 
+config ARM_ERRATA_742230
+       bool "ARM errata: DMB operation may be faulty"
+       depends on CPU_V7 && SMP
+       help
+         This option enables the workaround for the 742230 Cortex-A9
+         (r1p0..r2p2) erratum. Under rare circumstances, a DMB instruction
+         between two write operations may not ensure the correct visibility
+         ordering of the two writes. This workaround sets a specific bit in
+         the diagnostic register of the Cortex-A9 which causes the DMB
+         instruction to behave as a DSB, ensuring the correct behaviour of
+         the two writes.
+
 config PL310_ERRATA_588369
        bool "Clean & Invalidate maintenance operations do not invalidate clean lines"
        depends on CACHE_L2X0 && ARCH_OMAP4

diff --git a/arch/arm/mm/proc-v7.S b/arch/arm/mm/proc-v7.S
index 1f16f9e..945f363 100644 (file)
--- a/arch/arm/mm/proc-v7.S
+++ b/arch/arm/mm/proc-v7.S
@@ -201,7 +201,7 @@ __v7_setup:
        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 @@ __v7_setup:
        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
+
+       /* 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
 
-2:     mov     r10, #0
+3:     mov     r10, #0
 #ifdef HARVARD_CACHE
        mcr     p15, 0, r10, c7, c5, 0          @ I+BTB cache invalidate
 #endif