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>
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 @@
*
* 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 @@
#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 @@
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 @@
if (!fast_calibrate)
panic("TSC frequency is ZERO");
}
+#endif
gd->arch.tsc_mhz = fast_calibrate;
return fast_calibrate;