[U-Boot] [PATCH V4 02/11] ARM: Introduce erratum workaround for 454179

[Nishanth Menon]

454179: Stale prediction may inhibit target address misprediction on
	next predicted taken branch
Impacts: Every Cortex-A8 processors with revision lower than r2p1
Work around:  Set IBE and disable branch size mispredict to 1

Also provide a hook for SoC specific handling to take place if needed.

Based on ARM errata Document revision 20.0 (13 Nov 2010)

Signed-off-by: Nishanth Menon <nm at ti.com>
---
 README                       |    1 +
 arch/arm/cpu/armv7/cp15.c    |    6 ++++++
 arch/arm/cpu/armv7/start.S   |   13 +++++++++++++
 arch/arm/include/asm/armv7.h |    2 ++
 4 files changed, 22 insertions(+)

diff --git a/README b/README
index 11ec37ba4a00..e538cf061286 100644
--- a/README
+++ b/README
@@ -624,6 +624,7 @@ The following options need to be configured:
 		NOTE: The following can be machine specific errata. These
 		do have ability to provide rudimentary version and machine
 		specific checks, but expect no product checks.
+		CONFIG_ARM_ERRATA_454179
 		CONFIG_ARM_ERRATA_798870
 
 - Driver Model
diff --git a/arch/arm/cpu/armv7/cp15.c b/arch/arm/cpu/armv7/cp15.c
index 8ac81c9ba147..b44c9f94a822 100644
--- a/arch/arm/cpu/armv7/cp15.c
+++ b/arch/arm/cpu/armv7/cp15.c
@@ -21,3 +21,9 @@ void __weak v7_arch_cp15_set_l2aux_ctrl(u32 l2actlr, u32 cpu_midr,
 {
 	asm volatile ("mcr p15, 1, %0, c15, c0, 0\n\t" : : "r"(l2actlr));
 }
+
+void __weak v7_arch_cp15_set_acr(u32 acr, u32 cpu_midr, u32 cpu_rev_comb,
+				 u32 cpu_variant, u32 cpu_rev)
+{
+	asm volatile ("mcr p15, 0, %0, c1, c0, 1\n\t" : : "r"(acr));
+}
diff --git a/arch/arm/cpu/armv7/start.S b/arch/arm/cpu/armv7/start.S
index 6fbc44e5bf74..1516ed675dac 100644
--- a/arch/arm/cpu/armv7/start.S
+++ b/arch/arm/cpu/armv7/start.S
@@ -185,6 +185,19 @@ ENTRY(cpu_init_cp15)
 skip_errata_798870:
 #endif
 
+#ifdef CONFIG_ARM_ERRATA_454179
+	cmp	r2, #0x21		@ Only on < r2p1
+	bge	skip_errata_454179
+
+	mrc	p15, 0, r0, c1, c0, 1	@ Read ACR
+	orr	r0, r0, #(0x3 << 6)	@ Set DBSM(BIT7) and IBE(BIT6) bits
+	push	{r1-r4}			@ Save the cpu info registers
+	b	v7_arch_cp15_set_acr
+	pop	{r1-r4}			@ Restore the cpu info - fall through
+
+skip_errata_454179:
+#endif
+
 	mov	pc, lr			@ back to my caller
 ENDPROC(cpu_init_cp15)
 
diff --git a/arch/arm/include/asm/armv7.h b/arch/arm/include/asm/armv7.h
index 30e0cc3cf3d5..434b34de0ce9 100644
--- a/arch/arm/include/asm/armv7.h
+++ b/arch/arm/include/asm/armv7.h
@@ -96,6 +96,8 @@ extern char __secure_end[];
 void v7_arch_cp15_set_l2aux_ctrl(u32 l2auxctrl, u32 cpu_midr,
 				 u32 cpu_rev_comb, u32 cpu_variant,
 				 u32 cpu_rev);
+void v7_arch_cp15_set_acr(u32 acr, u32 cpu_midr, u32 cpu_rev_comb,
+			  u32 cpu_variant, u32 cpu_rev);
 #endif /* ! __ASSEMBLY__ */
 
 #endif
-- 
1.7.9.5