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x86: Allow a hardcoded TSC frequency provided by Kconfig

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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>
This commit is contained in:
Bin Meng 2015-01-06 22:14:14 +08:00 • committed by Simon Glass
parent 5c564b0d2f
commit 3ba6a0f4f6
2 changed files with 26 additions and 2 deletions
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8
arch/x86/lib/tsc_timer.c
View file

@ -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;