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Subject[PATCH v2] arm: remove unused code in delay.S
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Date
Document #if 0 code block in delay.S and make it selectable for compile.

Signed-off-by: Steve Chen <schen@mvista.com>

---
arch/arm/Kconfig | 14 ++++++++++++++
arch/arm/lib/delay.S | 2 +-
2 files changed, 15 insertions(+), 1 deletions(-)
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index aef63c8..ed8bf14 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -813,6 +813,20 @@ config ARM_ERRATA_460075
ACTLR register. Note that setting specific bits in the ACTLR
register
may not be available in non-secure mode.

+config OLD_CPU_DELAY
+ depends on CPU_32v3 || CPU_32v4 || CPU_32v4T
+ bool "Different delay() code for some older CPUs"
+ def_bool n
+ help
+ Enable this if observing longer than expected delays. This code
+ improves delay accuracy for some CPUs. However, it can also cause
+ delay duration to be too short for others which leads to stability
+ issues.
+
+ In other words, do not enable unless you can guarantee that the
+ processor (or ALL of the processors if building a generic kernel)
+ delays for at least the time requested after enabling.
+
endmenu

source "arch/arm/common/Kconfig"
diff --git a/arch/arm/lib/delay.S b/arch/arm/lib/delay.S
index 8d6a876..67e679b 100644
--- a/arch/arm/lib/delay.S
+++ b/arch/arm/lib/delay.S
@@ -42,7 +42,7 @@ ENTRY(__const_udelay) @ 0 <= r0 <= 0x7fffff06
@ Delay routine
ENTRY(__delay)
subs r0, r0, #1
-#if 0
+#ifdef CONFIG_OLD_CPU_DELAY
movls pc, lr
subs r0, r0, #1
movls pc, lr



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