[U-Boot] [PATCH V3 02/11] ARM: Introduce erratum workaround for 454179

Nishanth Menon
2015-02-25T20:55:10Z

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@ti.com>
---
README | 1 +
arch/arm/cpu/armv7/cp15.c | 6 ++++++
arch/arm/cpu/armv7/start.S | 11 +++++++++++
arch/arm/include/asm/armv7.h | 2 ++
4 files changed, 20 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 ec46cec9cb1c..1f20e12b92f9 100644
--- a/arch/arm/cpu/armv7/start.S
+++ b/arch/arm/cpu/armv7/start.S
@@ -183,6 +183,17 @@ ENTRY(cpu_init_cp15)
skip_errata_798870:
#endif

+#ifdef CONFIG_ARM_ERRATA_454179
+ cmp r2, #0x21 @ Only on < r2p1
+ blt skip_errata_454179
+
+ mrc p15, 0, r0, c1, c0, 1 @ Read ACR
+ orr r0, r0, #(0x3 << 6) @ Set DBSM(BIT7) and IBE(BIT6) bits
+ b v7_arch_cp15_set_acr
+
+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