timer: add tsctimer_setfreq()

Add function to set tsc frequency directly, without calibration.
Also tweak timer setup functions a bit: skip setup in case TimerPort
has not the default value any more, i.e. another timer has been setup
already.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Message-id: 20200310102248.28412-1-kraxel@redhat.com
diff --git a/src/hw/timer.c b/src/hw/timer.c
index bdcb3bf..56bb289 100644
--- a/src/hw/timer.c
+++ b/src/hw/timer.c
@@ -101,8 +101,10 @@
 void
 timer_setup(void)
 {
-    if (!CONFIG_TSC_TIMER || (CONFIG_PMTIMER && TimerPort != PORT_PIT_COUNTER0))
+    if (!CONFIG_TSC_TIMER)
         return;
+    if (TimerPort != PORT_PIT_COUNTER0)
+        return; // have timer already
 
     // Check if CPU has a timestamp counter
     u32 eax, ebx, ecx, edx, cpuid_features = 0;
@@ -114,10 +116,32 @@
 }
 
 void
+tsctimer_setfreq(u32 khz, const char *src)
+{
+    if (!CONFIG_TSC_TIMER)
+        return;
+    if (TimerPort != PORT_PIT_COUNTER0)
+        return; // have timer already
+
+    TimerKHz = khz;
+    ShiftTSC = 0;
+    while (TimerKHz >= 6000) {
+        ShiftTSC++;
+        TimerKHz = (TimerKHz + 1) >> 1;
+    }
+    TimerPort = 0;
+
+    dprintf(1, "CPU Mhz=%u (%s)\n", (TimerKHz << ShiftTSC) / 1000, src);
+}
+
+void
 pmtimer_setup(u16 ioport)
 {
     if (!CONFIG_PMTIMER)
         return;
+    if (TimerPort != PORT_PIT_COUNTER0)
+        return; // have timer already
+
     dprintf(1, "Using pmtimer, ioport 0x%x\n", ioport);
     TimerPort = ioport;
     TimerKHz = DIV_ROUND_UP(PMTIMER_HZ, 1000);
diff --git a/src/util.h b/src/util.h
index d96db78..94592a2 100644
--- a/src/util.h
+++ b/src/util.h
@@ -171,6 +171,7 @@
 // hw/timer.c
 void timer_setup(void);
 void pmtimer_setup(u16 ioport);
+void tsctimer_setfreq(u32 khz, const char *src);
 u32 timer_calc(u32 msecs);
 u32 timer_calc_usec(u32 usecs);
 int timer_check(u32 end);