[PATCH] ARM: errata: Workaround for Cortex-A12 erratum 818325

[Kever Yang]

From: Huang Tao <huangtao at rock-chips.com>

On Cortex-A12 (r0p0..r0p1-00lac0-rc11), when a CPU executes a sequence of
two conditional store instructions with opposite condition code and
updating the same register, the system might enter a deadlock if the
second conditional instruction is an UNPREDICTABLE STR or STM
instruction. This workaround setting bit[12] of the Feature Register
prevents the erratum. This bit disables an optimisation applied to a
sequence of 2 instructions that use opposing condition codes.

Signed-off-by: Huang Tao <huangtao at rock-chips.com>
Signed-off-by: Kever Yang <kever.yang at rock-chips.com>
---

 arch/arm/Kconfig      | 13 +++++++++++++
 arch/arm/mm/proc-v7.S | 15 ++++++++++++++-
 2 files changed, 27 insertions(+), 1 deletion(-)

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 32cbbd5..4545835 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -1245,6 +1245,19 @@ config ARM_ERRATA_773022
 	  loop buffer may deliver incorrect instructions. This
 	  workaround disables the loop buffer to avoid the erratum.
 
+config ARM_ERRATA_818325
+	bool "ARM errata: Execution of an UNPREDICTABLE STR or STM instruction might deadlock"
+	depends on CPU_V7
+	help
+	  This option enables the workaround for the 818325 Cortex-A12
+	  (r0p0..r0p1-00lac0-rc11) erratum. When a CPU executes a sequence of
+	  two conditional store instructions with opposite condition code and
+	  updating the same register, the system might enter a deadlock if the
+	  second conditional instruction is an UNPREDICTABLE STR or STM
+	  instruction. This workaround setting bit[12] of the Feature Register
+	  prevents the erratum. This bit disables an optimisation applied to a
+	  sequence of 2 instructions that use opposing condition codes.
+
 endmenu
 
 source "arch/arm/common/Kconfig"
diff --git a/arch/arm/mm/proc-v7.S b/arch/arm/mm/proc-v7.S
index b5d67db..5ffdf97 100644
--- a/arch/arm/mm/proc-v7.S
+++ b/arch/arm/mm/proc-v7.S
@@ -408,7 +408,20 @@ __v7_setup:
 	mcrle	p15, 0, r10, c1, c0, 1		@ write aux control register
 #endif
 
-4:	mov	r10, #0
+	/* Cortex-A12 Errata */
+4:	ldr	r10, =0x00000c0d		@ Cortex-A12 primary part number
+	teq	r0, r10
+	bne	5f
+#ifdef CONFIG_ARM_ERRATA_818325
+	teq	r6, #0x00			@ present in r0p0
+	teqne	r6, #0x01			@ present in r0p1-00lac0-rc11
+	mrceq	p15, 0, r10, c15, c0, 1		@ read diagnostic register
+	orreq	r10, r10, #1 << 12		@ set bit #12
+	mcreq	p15, 0, r10, c15, c0, 1		@ write diagnostic register
+	isb
+#endif
+
+5:	mov	r10, #0
 	mcr	p15, 0, r10, c7, c5, 0		@ I+BTB cache invalidate
 #ifdef CONFIG_MMU
 	mcr	p15, 0, r10, c8, c7, 0		@ invalidate I + D TLBs
-- 
1.8.3.2