Allow use of Pentium cycle counter for high-precision time keeping;

from FreeBSD

5 files changed, 78 insertions, 6 deletions

diff --git a/sys/arch/i386/i386/autoconf.c b/sys/arch/i386/i386/autoconf.c
index a1ab9c17e31..b02546e3577 100644
--- a/sys/arch/i386/i386/autoconf.c
+++ b/sys/arch/i386/i386/autoconf.c
@@ -70,9 +70,6 @@ extern int	cold;		/* cold start flag initialized in locore.s */
  */
 configure()
 {
-
-	startrtclock();
-
 	config_rootfound("isa", NULL);
 	config_rootfound("eisa", NULL);
 	config_rootfound("pci", NULL);
diff --git a/sys/arch/i386/i386/machdep.c b/sys/arch/i386/i386/machdep.c
index 46a1e5bf534..9139f31dfd8 100644
--- a/sys/arch/i386/i386/machdep.c
+++ b/sys/arch/i386/i386/machdep.c
@@ -165,6 +165,7 @@ cpu_startup()
 	msgbufmapped = 1;
 
 	printf(version);
+	startrtclock();
 	identifycpu();
 	printf("real mem  = %d\n", ctob(physmem));
 
@@ -390,7 +391,14 @@ identifycpu()
 		break;
 	}
 	strcat(cpu_model, "-class CPU)");
-	printf("%s\n", cpu_model);	/* cpu speed would be nice, but how? */
+	printf("%s", cpu_model);	/* cpu speed would be nice, but how? */
+#if defined(I586_CPU)
+	if (cpu_class == CPUCLASS_586) {
+		calibrate_cyclecounter();
+		printf(" %d MHz", pentium_mhz);
+	}
+#endif
+	printf("\n");
 
 	/*
 	 * Now that we have told the user what they have,
diff --git a/sys/arch/i386/i386/microtime.s b/sys/arch/i386/i386/microtime.s
index 95ef8dc1a8a..fc2f33ab268 100644
--- a/sys/arch/i386/i386/microtime.s
+++ b/sys/arch/i386/i386/microtime.s
@@ -46,13 +46,21 @@
  */
 #ifndef HZ
 ENTRY(microtime)
-	cli				# disable interrupts
 
+#ifdef I586_CPU
+	movl	_pentium_mhz, %ecx
+	testl	%ecx, %ecx
+	jne	pentium_microtime
+#else
+	xorl	%ecx,%ecx
+#endif
 	movb	$(TIMER_SEL0|TIMER_LATCH),%al
+
+	cli				# disable interrupts
+
 	outb	%al,$TIMER_MODE		# latch timer 0's counter
 
 	# Read counter value into ecx, LSB first
-	xorl	%ecx,%ecx
 	inb	$TIMER_CNTR0,%al
 	movb	%al,%cl
 	inb	$TIMER_CNTR0,%al
@@ -111,6 +119,7 @@ ENTRY(microtime)
 	leal	(%edx,%eax,8),%eax	# a = 8a + d = 3433d
 	shrl	$12,%eax		# a = a/4096 = 3433d/4096
 
+common_microtime:
 	movl	_time,%edx	# get time.tv_sec
 	addl	_time+4,%eax	# add time.tv_usec
 
@@ -126,4 +135,14 @@ ENTRY(microtime)
 	movl	%eax,4(%ecx)	# tvp->tv_usec = usec
 
 	ret
+
+#ifdef I586_CPU
+	.align	2, 0x90
+pentium_microtime:
+	cli
+	.byte	0x0f, 0x31	# RDTSC
+	divl	%ecx		# convert to usec
+	jmp	common_microtime
+#endif
+
 #endif
diff --git a/sys/arch/i386/include/cpu.h b/sys/arch/i386/include/cpu.h
index b8fcdd48720..6d6c439e6ac 100644
--- a/sys/arch/i386/include/cpu.h
+++ b/sys/arch/i386/include/cpu.h
@@ -94,6 +94,34 @@ int	want_resched;		/* resched() was called */
  */
 #define	DELAY(x)		delay(x)
 
+#ifdef I586_CPU
+/*
+ * High resolution clock support (Pentium only)
+ */
+#define CPU_CLOCKUPDATE(otime, ntime) \
+	do { \
+		if (pentium_mhz) { \
+			__asm __volatile("cli\n" \
+					 "movl (%2), %%eax\n" \
+					 "movl %%eax, (%1)\n" \
+					 "movl 4(%2), %%eax\n" \
+					 "movl %%eax, 4(%1)\n" \
+					 "movl $0x10, %%ecx\n" \
+					 "xorl %%eax, %%eax\n" \
+					 "movl %%eax, %%edx\n" \
+					 ".byte 0xf, 0x30\n" \
+					 "sti\n" \
+					 "#%0%1%2" \
+					 : "=m" (*otime) \
+					 : "c" (otime), "b" (ntime) \
+					 : "ax", "cx", "dx"); \
+		} \
+		else { \
+			*(otime) = *(ntime); \
+		} \
+	} while (0)
+#endif
+
 /*
  * pull in #defines for kinds of processors
  */
@@ -108,6 +136,9 @@ struct cpu_nameclass {
 extern int cpu;
 extern int cpu_class;
 extern struct cpu_nameclass i386_cpus[];
+#ifdef I586_CPU
+extern int pentium_mhz;
+#endif
 #endif
 
 /* 
diff --git a/sys/arch/i386/isa/clock.c b/sys/arch/i386/isa/clock.c
index 5cacb8cc9fc..2833d2f2f10 100644
--- a/sys/arch/i386/isa/clock.c
+++ b/sys/arch/i386/isa/clock.c
@@ -107,6 +107,10 @@ WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 
 void spinwait __P((int));
 
+#ifdef I586_CPU
+int pentium_mhz;
+#endif
+
 #define	SECMIN	((unsigned)60)			/* seconds per minute */
 #define	SECHOUR	((unsigned)(60*SECMIN))		/* seconds per hour */
 #define	SECDAY	((unsigned)(24*SECHOUR))	/* seconds per day */
@@ -303,6 +307,19 @@ findcpuspeed()
 	delaycount = (FIRST_GUESS * TIMER_DIV(1000)) / (0xffff-remainder);
 }
 
+#ifdef I586_CPU
+void
+calibrate_cyclecounter()
+{
+	unsigned long long count, last_count;
+
+	__asm __volatile(".byte 0xf, 0x31" : "=A" (last_count));
+	delay(1000000);
+	__asm __volatile(".byte 0xf, 0x31" : "=A" (count));
+	pentium_mhz = ((count - last_count) + 500000) / 1000000;
+}
+#endif
+
 void
 cpu_initclocks()
 {