From 8e73b5d9528401a50254eb968080b814b5418152 Mon Sep 17 00:00:00 2001 From: Aaron Durbin Date: Wed, 1 May 2013 15:27:09 -0500 Subject: x86: add TSC_CONSTANT_RATE option Some boards use the local apic for udelay(), but they also provide their own implementation of udelay() for SMM. The reason for using the local apic for udelay() in ramstage is to not have to pay the penalty of calibrating the TSC frequency. Therefore provide a TSC_CONSTANT_RATE option to indicate that TSC calibration is not needed. Instead rely on the presence of a tsc_freq_mhz() function provided by the cpu/board. Additionally, assume that if TSC_CONSTANT_RATE is selected the udelay() function in SMM will be the tsc. Change-Id: I1629c2fbe3431772b4e80495160584fb6f599e9e Signed-off-by: Aaron Durbin Reviewed-on: http://review.coreboot.org/3168 Tested-by: build bot (Jenkins) Reviewed-by: Paul Menzel Reviewed-by: Ronald G. Minnich --- src/cpu/x86/Kconfig | 7 +++++++ 1 file changed, 7 insertions(+) (limited to 'src/cpu/x86/Kconfig') diff --git a/src/cpu/x86/Kconfig b/src/cpu/x86/Kconfig index 5cf40fa4a9..c64a8e477b 100644 --- a/src/cpu/x86/Kconfig +++ b/src/cpu/x86/Kconfig @@ -25,6 +25,13 @@ config UDELAY_TSC bool default n +config TSC_CONSTANT_RATE + def_bool n + depends on UDELAY_TSC + help + This option asserts that the TSC ticks at a known constant rate. + Therefore, no TSC calibration is required. + config TSC_MONOTONIC_TIMER def_bool n depends on UDELAY_TSC -- cgit v1.2.3