APIC disabled if CPU lacks TSC

- we cannot calibrate local APIC timer in such a case

- fixes possible uninitialized variable problem during calibration if no TSC

diff --git a/kernel/arch/i386/apic.c b/kernel/arch/i386/apic.c
index 7143aa6e30ce9d33c2a25e0c14531034825b09e8..126010441d0599478f96e5d8b36d7c15bfeabb2a 100644 (file)
--- a/kernel/arch/i386/apic.c
+++ b/kernel/arch/i386/apic.c
@@ -155,9 +155,7 @@ PRIVATE int calib_clk_handler(irq_hook_t * hook)
        u64_t tsc;
 
        probe_ticks++;
-       if (cpu_has_tsc) {
-               read_tsc_64(&tsc);
-       }
+       read_tsc_64(&tsc);
        tcrt = lapic_read(LAPIC_TIMER_CCR);
 
 
@@ -385,6 +383,13 @@ PUBLIC int lapic_enable(void)
        if (!lapic_addr)
                return 0;
 
+       cpu_has_tsc = _cpufeature(_CPUF_I386_TSC);
+       if (!cpu_has_tsc) {
+               kprintf("CPU lacks timestamp counter, "
+                       "cannot calibrate LAPIC timer\n");
+               return 0;
+       }
+
        if (!lapic_enable_in_msr())
                return 0;
 
@@ -439,10 +444,6 @@ PUBLIC int lapic_enable(void)
        lapic_read (LAPIC_SIVR);
        *((u32_t *)lapic_eoi_addr) = 0;
 
-
-       cpu_has_tsc = _cpufeature(_CPUF_I386_TSC);
-       BOOT_VERBOSE(if (cpu_has_tsc) kprintf("CPU has Timestamp counter\n"));
-
        apic_calibrate_clocks();
        BOOT_VERBOSE(kprintf("APIC timer calibrated\n"));