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
---
Changes in v2: - Spell out TSC, MSR and PIT in the Kconfig help
arch/x86/Kconfig | 20 ++++++++++++++++++++ arch/x86/lib/tsc_timer.c | 8 ++++++-- 2 files changed, 26 insertions(+), 2 deletions(-)
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index ebf72b3..4bd945e 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -317,6 +317,26 @@ config FRAMEBUFFER_VESA_MODE
endmenu
+config TSC_CALIBRATION_BYPASS + bool "Bypass Time-Stamp Counter (TSC) calibration" + default n + help + By default U-Boot automatically calibrates Time-Stamp Counter (TSC) + running frequency via Model-Specific Register (MSR) and Programmable + Interval Timer (PIT). If the calibration does not work on your board, + select this option and provide a hardcoded TSC running frequency with + CONFIG_TSC_FREQ_IN_MHZ below. + + Normally this option should be turned on in a simulation environment + like qemu. + +config TSC_FREQ_IN_MHZ + int "Time-Stamp Counter (TSC) running frequency in MHz" + depends on TSC_CALIBRATION_BYPASS + default 1000 + help + The running frequency in MHz of Time-Stamp Counter (TSC). + source "arch/x86/cpu/ivybridge/Kconfig"
source "arch/x86/cpu/queensbay/Kconfig" diff --git a/arch/x86/lib/tsc_timer.c b/arch/x86/lib/tsc_timer.c index fb9afed..7f5ba2c 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;