diff options
| author | Aaron Durbin <adurbin@chromium.org> | 2013-05-01 15:27:09 -0500 |
|---|---|---|
| committer | Ronald G. Minnich <rminnich@gmail.com> | 2013-05-07 18:35:04 +0200 |
| commit | 8e73b5d9528401a50254eb968080b814b5418152 (patch) | |
| tree | eb63210a3be8114f72894c9ff78fbc70fb4d2426 /src/cpu/x86/Kconfig | |
| parent | 7cb1ba9a61b244800eb65c08729f75d85a504de3 (diff) | |
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 <adurbin@chromium.org>
Reviewed-on: http://review.coreboot.org/3168
Tested-by: build bot (Jenkins)
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>
Diffstat (limited to 'src/cpu/x86/Kconfig')
| -rw-r--r-- | src/cpu/x86/Kconfig | 7 |
1 files changed, 7 insertions, 0 deletions
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 |