55 lines
1.7 KiB
C
55 lines
1.7 KiB
C
#include <zinnia/clock.h>
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#include <zinnia/cmdline.h>
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#include <zinnia/print.h>
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#include <x86_64/asm.h>
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#include <x86_64/defs.h>
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static bool use_tsc = true;
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void tsc_init() {
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if (!use_tsc)
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return;
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if (!(asm_cpuid(1, 0).edx & CPUID_1D_TSC) || !(asm_cpuid(0x8000'0007, 0).edx & (1 << 8))) {
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printf("No invariant TSC detected!\n");
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return;
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}
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// Check for the TSC info leaf.
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bool has_tsc_leaf = false;
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struct cpuid tsc_leaf = {0};
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if (asm_cpuid(0x8000'0000, 0).eax >= 0x15) {
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tsc_leaf = asm_cpuid(0x15, 0);
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}
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uint64_t freq = 0;
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if (clock_available()) {
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// Calibrate using existing clock.
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uint64_t t1 = asm_rdtsc();
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clock_spin_ns(10'000'000);
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uint64_t t2 = asm_rdtsc();
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freq = (t2 - t1) * 100;
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} else if (has_tsc_leaf) {
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// If we have no timer (yet), the only way we can calibrate the TSC is if CPUID gives us the frequency.
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// On a normal system, this should usually never be called and is a last resort
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// since at this point we have at least the HPET timer.
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if (tsc_leaf.ecx != 0 && tsc_leaf.ebx != 0 && tsc_leaf.eax != 0) {
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printf("Calibrating TSC using CPUID 0x15");
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freq = tsc_leaf.ecx * tsc_leaf.ebx / tsc_leaf.eax;
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} else {
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printf("Unable to calibrate TSC using CPUID frequency information");
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return;
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}
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} else {
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printf("Unable to calibrate the TSC without a clock or static frequency info!\n");
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return;
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}
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printf("Timer frequency is %lu MHz\n", freq / 1'000'000);
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}
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static void tsc_option(bool opt) {
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use_tsc = opt;
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}
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CMDLINE_OPTION("tsc", tsc_option);
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