+static void
+calibrate_tsc(void)
+{
+ u32 eax, ebx, ecx, edx, cpuid_features = 0;
+ cpuid(0, &eax, &ebx, &ecx, &edx);
+ if (eax > 0)
+ cpuid(1, &eax, &ebx, &ecx, &cpuid_features);
+
+ if (!(cpuid_features & CPUID_TSC)) {
+ SET_GLOBAL(no_tsc, 1);
+ SET_GLOBAL(cpu_khz, PIT_TICK_RATE / 1000);
+ dprintf(3, "386/486 class CPU. Using TSC emulation\n");
+ return;
+ }
+
+ // Setup "timer2"
+#if 0
+ u8 orig = inb(PORT_PS2_CTRLB);
+ outb((orig & ~PPCB_SPKR) | PPCB_T2GATE, PORT_PS2_CTRLB);
+ /* binary, mode 0, LSB/MSB, Ch 2 */
+ outb(PM_SEL_TIMER2|PM_ACCESS_WORD|PM_MODE0|PM_CNT_BINARY, PORT_PIT_MODE);
+ /* LSB of ticks */
+ outb(CALIBRATE_COUNT & 0xFF, PORT_PIT_COUNTER2);
+ /* MSB of ticks */
+ outb(CALIBRATE_COUNT >> 8, PORT_PIT_COUNTER2);
+
+ u64 start = rdtscll();
+ while ((inb(PORT_PS2_CTRLB) & PPCB_T2OUT) == 0)
+ ;
+ u64 end = rdtscll();
+
+ // Restore PORT_PS2_CTRLB
+ outb(orig, PORT_PS2_CTRLB);
+
+ // Store calibrated cpu khz.
+ u64 diff = end - start;
+ dprintf(6, "tsc calibrate start=%u end=%u diff=%u\n"
+ , (u32)start, (u32)end, (u32)diff);
+ u32 hz = diff * PIT_TICK_RATE / CALIBRATE_COUNT;
+ SET_GLOBAL(cpu_khz, hz / 1000);
+#else
+ u32 hz = 800 * 1000000;
+ SET_GLOBAL(cpu_khz, hz / 1000);
+#endif
+
+ dprintf(1, "CPU Mhz=%u\n", hz / 1000000);
+}
+
+static u64
+emulate_tsc(void)
+{
+ int cnt, d;
+ u16 ebda_seg = get_ebda_seg();
+ u64 ret;
+ /* read timer 0 current count */
+ ret = GET_EBDA2(ebda_seg, tsc_8254);
+ /* readback mode has slightly shifted registers, works on all 8254, readback PIT0 latch */
+ outb(PM_SEL_READBACK | PM_READ_VALUE | PM_READ_COUNTER0, PORT_PIT_MODE);
+ cnt = (inb(PORT_PIT_COUNTER0) | (inb(PORT_PIT_COUNTER0) << 8));
+ d = GET_EBDA2(ebda_seg, last_tsc_8254) - cnt;
+ /* Determine the ticks count from last invocation of this function */
+ ret += (d > 0) ? d : (PIT_TICK_INTERVAL + d);
+ SET_EBDA2(ebda_seg, last_tsc_8254, cnt);
+ SET_EBDA2(ebda_seg, tsc_8254, ret);
+ return ret;
+}
+
+static u64
+get_tsc(void)
+{
+ if (unlikely(GET_GLOBAL(no_tsc)))
+ return emulate_tsc();
+ return rdtscll();
+}
+
+int
+check_tsc(u64 end)
+{
+ return (s64)(get_tsc() - end) > 0;
+}