[PATCH v1] ARM: errata: Workaround for Cortex-A12 erratum 818325

[Caesar Wang]

From: Huang Tao <huangtao@xxxxxxxxxxxxxx>

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@xxxxxxxxxxxxxx>
Signed-off-by: Kever Yang <kever.yang@xxxxxxxxxxxxxx>
Signed-off-by: Caesar Wang <wxt@xxxxxxxxxxxxxx>

---

Changes in v1:
- fix the build error.

 arch/arm/Kconfig      | 13 +++++++++++++
 arch/arm/mm/proc-v7.S | 16 ++++++++++++++++
 2 files changed, 29 insertions(+)

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 639411f..554b57a 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -1263,6 +1263,19 @@ 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 de2b246..e95c83c 100644
--- a/arch/arm/mm/proc-v7.S
+++ b/arch/arm/mm/proc-v7.S
@@ -351,6 +351,17 @@ __ca9_errata:
 #endif
 	b	__errata_finish
 
+__ca12_errata:
+#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
+	b	__errata_finish
+
 __ca15_errata:
 #ifdef CONFIG_ARM_ERRATA_773022
 	cmp	r6, #0x4			@ only present up to r0p4
@@ -439,6 +450,11 @@ __v7_setup_cont:
 	teq	r0, r10
 	beq	__ca9_errata
 
+	/* Cortex-A12 Errata */
+	ldr	r10, =0x00000c0d		@ Cortex-A12 primary part number
+	teq	r0, r10
+	beq	__ca12_errata
+
 	/* Cortex-A15 Errata */
 	ldr	r10, =0x00000c0f		@ Cortex-A15 primary part number
 	teq	r0, r10
-- 
1.9.1

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