Allow users to remove the CPU timestamp counter support at compile
time. The PMTIMER is frequently used instead of the TSC and this
compile time option allows one to strip a few bytes from the final
binary. This change also defaults the internal timer to use the PIT
based timer until the PMTIMER or TSC is detected.
Signed-off-by: Kevin O'Connor <kevin(a)koconnor.net>
---
src/Kconfig | 10 ++++++++--
src/hw/timer.c | 23 ++++++++---------------
2 files changed, 16 insertions(+), 17 deletions(-)
diff --git a/src/Kconfig b/src/Kconfig
index 14c38fb..b14e554 100644
--- a/src/Kconfig
+++ b/src/Kconfig
@@ -316,10 +316,16 @@ menu "Hardware support"
help
Initialize the Memory Type Range Registers (on emulators).
config PMTIMER
- bool "Use ACPI timer"
+ bool "Support ACPI timer"
default y
help
- Use the ACPI timer instead of the TSC for timekeeping (on qemu).
+ Detect and use the ACPI timer for timekeeping.
+ config TSC_TIMER
+ bool "Support CPU timestamp counter as timer"
+ default y
+ help
+ Support for using the CPU timestamp counter as an internal
+ timing source.
endmenu
menu "BIOS interfaces"
diff --git a/src/hw/timer.c b/src/hw/timer.c
index 5edc9fd..882b772 100644
--- a/src/hw/timer.c
+++ b/src/hw/timer.c
@@ -49,8 +49,8 @@
#define PMTIMER_HZ 3579545 // Underlying Hz of the PM Timer
#define PMTIMER_TO_PIT 3 // Ratio of pmtimer rate to pit rate
-u32 TimerKHz VARFSEG;
-u16 TimerPort VARFSEG;
+u32 TimerKHz VARFSEG = DIV_ROUND_UP(PMTIMER_HZ, 1000 * PMTIMER_TO_PIT);
+u16 TimerPort VARFSEG = PORT_PIT_COUNTER0;
u8 ShiftTSC VARFSEG;
@@ -92,6 +92,7 @@ tsctimer_setup(void)
t = (t + 1) >> 1;
}
TimerKHz = DIV_ROUND_UP((u32)t, 1000 * PMTIMER_TO_PIT);
+ TimerPort = 0;
dprintf(1, "CPU Mhz=%u\n", (TimerKHz << ShiftTSC) / 1000);
}
@@ -100,24 +101,16 @@ tsctimer_setup(void)
void
timer_setup(void)
{
- if (CONFIG_PMTIMER && TimerPort) {
- dprintf(3, "pmtimer already configured; will not calibrate TSC\n");
+ if (!CONFIG_TSC_TIMER || (CONFIG_PMTIMER && TimerPort != PORT_PIT_COUNTER0))
return;
- }
+ // Check if CPU has a timestamp counter
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)) {
- TimerPort = PORT_PIT_COUNTER0;
- TimerKHz = DIV_ROUND_UP(PMTIMER_HZ, 1000 * PMTIMER_TO_PIT);
- dprintf(3, "386/486 class CPU. Using TSC emulation\n");
- return;
- }
-
- tsctimer_setup();
+ if (cpuid_features & CPUID_TSC)
+ tsctimer_setup();
}
void
@@ -154,7 +147,7 @@ static u32
timer_read(void)
{
u16 port = GET_GLOBAL(TimerPort);
- if (!port)
+ if (CONFIG_TSC_TIMER && !port)
// Read from CPU TSC
return rdtscll() >> GET_GLOBAL(ShiftTSC);
if (CONFIG_PMTIMER && port != PORT_PIT_COUNTER0)
--
1.9.3