From: Tomas Hruby <tom@minix3.org>
Date: Wed, 13 Jan 2010 18:22:41 +0000 (+0000)
Subject: APIC disabled if CPU lacks TSC
X-Git-Tag: v3.1.6~87
X-Git-Url: http://zhaoyanbai.com/repos/%22http:/www.isc.org/icons/zpipe.c?a=commitdiff_plain;h=42c13951a7df0d504d425e029fcdfda3ac25cb65;p=minix.git

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 7143aa6e3..126010441 100644
--- 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"));