[U-Boot] [PATCH 1/3] ARM: implement some Cortex-A9 errata workarounds

[Stephen Warren]

From: Stephen Warren <swarren at nvidia.com>

Various errata exist in the Cortex-A9 CPU, and may be worked around by
setting some bits in a CP15 diagnostic register. Add code to implement
the workarounds, enabled by new CONFIG_ options.

This code was taken from the Linux kernel, v3.8, arch/arm/mm/proc-v7.S,
and modified to remove the logic to conditionally apply the WAR (since we
know exactly which CPU we're running on given the U-Boot configuration),
and use r0 instead of r10 for consistency with the rest of U-Boot's
cpu_init_cp15().

Signed-off-by: Stephen Warren <swarren at nvidia.com>
---
 README                     |   10 ++++++++++
 arch/arm/cpu/armv7/start.S |   19 +++++++++++++++++++
 2 files changed, 29 insertions(+)

diff --git a/README b/README
index d8cb394..f2b1c88 100644
--- a/README
+++ b/README
@@ -485,6 +485,16 @@ The following options need to be configured:
 		Thumb2 this flag will result in Thumb2 code generated by
 		GCC.
 
+		CONFIG_ARM_ERRATA_742230
+		CONFIG_ARM_ERRATA_743622
+		CONFIG_ARM_ERRATA_751472
+
+		If set, the workarounds for these ARM errata are applied early
+		during U-Boot startup. Note that these options force the
+		workarounds to be applied; no CPU-type/version detection
+		exists, unlike the similar options in the Linux kernel. Do not
+		set these options unless they apply!
+
 - Linux Kernel Interface:
 		CONFIG_CLOCKS_IN_MHZ
 
diff --git a/arch/arm/cpu/armv7/start.S b/arch/arm/cpu/armv7/start.S
index 6b59529d..30f02d3 100644
--- a/arch/arm/cpu/armv7/start.S
+++ b/arch/arm/cpu/armv7/start.S
@@ -309,6 +309,25 @@ ENTRY(cpu_init_cp15)
 	orr	r0, r0, #0x00001000	@ set bit 12 (I) I-cache
 #endif
 	mcr	p15, 0, r0, c1, c0, 0
+
+#ifdef CONFIG_ARM_ERRATA_742230
+	mrc	p15, 0, r0, c15, c0, 1	@ read diagnostic register
+	orr	r0, r0, #1 << 4		@ set bit #4
+	mcr	p15, 0, r0, c15, c0, 1	@ write diagnostic register
+#endif
+
+#ifdef CONFIG_ARM_ERRATA_743622
+	mrc	p15, 0, r0, c15, c0, 1	@ read diagnostic register
+	orr	r0, r0, #1 << 6		@ set bit #6
+	mcr	p15, 0, r0, c15, c0, 1	@ write diagnostic register
+#endif
+
+#ifdef CONFIG_ARM_ERRATA_751472
+	mrc	p15, 0, r0, c15, c0, 1	@ read diagnostic register
+	orr	r0, r0, #1 << 11	@ set bit #11
+	mcr	p15, 0, r0, c15, c0, 1	@ write diagnostic register
+#endif
+
 	mov	pc, lr			@ back to my caller
 ENDPROC(cpu_init_cp15)
 
-- 
1.7.10.4