diff options
| author | Bin Meng <bmeng.cn@gmail.com> | 2015-01-06 22:14:14 +0800 |
|---|---|---|
| committer | Simon Glass <sjg@chromium.org> | 2015-01-13 07:25:02 -0800 |
| commit | 3ba6a0f4f6a2381ad32930df6277930a3de577bc (patch) | |
| tree | 218fdbde4e70eeab4b65543757677b3ca5864229 /arch/x86/lib/tsc_timer.c | |
| parent | 5c564b0d2fd108ebc5fd6bb0081b981ee32ddf0b (diff) | |
x86: Allow a hardcoded TSC frequency provided by Kconfig
By default U-Boot automatically calibrates TSC running frequency via
MSR and PIT. The calibration may not work on every x86 processor, so
a new Kconfig option CONFIG_TSC_CALIBRATION_BYPASS is introduced to
allow bypassing the calibration and assign a hardcoded TSC frequency
CONFIG_TSC_FREQ_IN_MHZ.
Normally the bypass should be turned on in a simulation environment
like qemu.
Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Acked-by: Simon Glass <sjg@chromium.org>
Diffstat (limited to 'arch/x86/lib/tsc_timer.c')
| -rw-r--r-- | arch/x86/lib/tsc_timer.c | 8 |
1 files changed, 6 insertions, 2 deletions
diff --git a/arch/x86/lib/tsc_timer.c b/arch/x86/lib/tsc_timer.c index fb9afed18f..7f5ba2ca6f 100644 --- a/arch/x86/lib/tsc_timer.c +++ b/arch/x86/lib/tsc_timer.c @@ -78,7 +78,7 @@ static int match_cpu(u8 family, u8 model) * * Returns the calibration value or 0 if MSR calibration failed. */ -static unsigned long try_msr_calibrate_tsc(void) +static unsigned long __maybe_unused try_msr_calibrate_tsc(void) { u32 lo, hi, ratio, freq_id, freq; unsigned long res; @@ -199,7 +199,7 @@ static inline int pit_expect_msb(unsigned char val, u64 *tscp, #define MAX_QUICK_PIT_MS 50 #define MAX_QUICK_PIT_ITERATIONS (MAX_QUICK_PIT_MS * PIT_TICK_RATE / 1000 / 256) -static unsigned long quick_pit_calibrate(void) +static unsigned long __maybe_unused quick_pit_calibrate(void) { int i; u64 tsc, delta; @@ -306,6 +306,9 @@ unsigned __attribute__((no_instrument_function)) long get_tbclk_mhz(void) if (gd->arch.tsc_mhz) return gd->arch.tsc_mhz; +#ifdef CONFIG_TSC_CALIBRATION_BYPASS + fast_calibrate = CONFIG_TSC_FREQ_IN_MHZ; +#else fast_calibrate = try_msr_calibrate_tsc(); if (!fast_calibrate) { @@ -313,6 +316,7 @@ unsigned __attribute__((no_instrument_function)) long get_tbclk_mhz(void) if (!fast_calibrate) panic("TSC frequency is ZERO"); } +#endif gd->arch.tsc_mhz = fast_calibrate; return fast_calibrate; |