1 files changed, 69 insertions, 0 deletions
diff --git a/gpxe/src/arch/i386/drivers/timer_rdtsc.c b/gpxe/src/arch/i386/drivers/timer_rdtsc.c
new file mode 100644
index 00000000..09b7df2f
--- /dev/null
+++ b/gpxe/src/arch/i386/drivers/timer_rdtsc.c
@@ -0,0 +1,69 @@
+
+#include <gpxe/init.h>
+#include <gpxe/timer.h>
+#include <errno.h>
+#include <stdio.h>
+#include <bits/cpu.h>
+#include <bits/timer2.h>
+#include <io.h>
+
+
+#define rdtsc(low,high) \
+     __asm__ __volatile__("rdtsc" : "=a" (low), "=d" (high))
+
+#define rdtscll(val) \
+     __asm__ __volatile__ ("rdtsc" : "=A" (val))
+
+
+/* Measure how many clocks we get in one microsecond */
+static inline uint64_t calibrate_tsc(void)
+{
+
+	uint64_t rdtsc_start;
+	uint64_t rdtsc_end;
+
+	rdtscll(rdtsc_start);
+	i386_timer2_udelay(USECS_IN_MSEC);
+	rdtscll(rdtsc_end);
+	
+	return (rdtsc_end - rdtsc_start) / USECS_IN_MSEC;
+}
+
+static uint32_t clocks_per_usec = 0;
+
+/* We measure time in microseconds. */
+static tick_t rdtsc_currticks(void)
+{
+	uint64_t clocks;
+
+	/* Read the Time Stamp Counter */
+	rdtscll(clocks);
+
+	return clocks / clocks_per_usec;
+}
+
+static int rdtsc_ts_init(void)
+{
+
+	struct cpuinfo_x86 cpu_info;
+
+	get_cpuinfo(&cpu_info);
+	if (cpu_info.features & X86_FEATURE_TSC) {
+		clocks_per_usec= calibrate_tsc();
+		if (clocks_per_usec) {
+			DBG("RDTSC ticksource installed. CPU running at %ld Mhz\n",
+				clocks_per_usec);
+			return 0;
+		}
+	}
+
+	DBG("RDTSC ticksource not available on this machine.\n");
+	return -ENODEV;
+}
+
+struct timer rdtsc_ts __timer (01) = {
+	.init = rdtsc_ts_init,
+	.udelay = generic_currticks_udelay,
+	.currticks = rdtsc_currticks,
+};
+