Only use the interval timer for clock interrupts on the BSP and

have the BSP use IPIs to trigger clock interrupts on the APs.
This allows us to run on hardware configurations for which the
ITC has non-uniform frequencies across CPUs.

While here, change the clock XIV to type IPI so as to protect
the interrupt delivery against CPU re-balancing once that's
implemented.

3 files changed, 55 insertions, 50 deletions

diff --git a/sys/ia64/ia64/clock.c b/sys/ia64/ia64/clock.c
index 2e7f2d8..33dbb2e 100644
--- a/sys/ia64/ia64/clock.c
+++ b/sys/ia64/ia64/clock.c
@@ -43,6 +43,7 @@ __FBSDID("$FreeBSD$");
 #include <machine/intr.h>
 #include <machine/intrcnt.h>
 #include <machine/md_var.h>
+#include <machine/smp.h>
 
 SYSCTL_NODE(_debug, OID_AUTO, clock, CTLFLAG_RW, 0, "clock statistics");
 
@@ -91,58 +92,61 @@ ia64_ih_clock(struct thread *td, u_int xiv, struct trapframe *tf)
 	int count;
 
 	PCPU_INC(md.stats.pcs_nclks);
-	intrcnt[INTRCNT_CLOCK]++;
 
-	itc = ia64_get_itc();
+	if (PCPU_GET(cpuid) == 0) {
+		/*
+		 * Clock processing on the BSP.
+		 */
+		intrcnt[INTRCNT_CLOCK]++;
 
-	adj = PCPU_GET(md.clockadj);
-	clk = PCPU_GET(md.clock);
+		itc = ia64_get_itc();
 
-	delta = itc - clk;
-	count = 0;
-	while (delta >= ia64_clock_reload) {
-		/* Only the BSP runs the real clock */
-		if (PCPU_GET(cpuid) == 0)
+		adj = PCPU_GET(md.clockadj);
+		clk = PCPU_GET(md.clock);
+
+		delta = itc - clk;
+		count = 0;
+		while (delta >= ia64_clock_reload) {
+#ifdef SMP
+			ipi_all_but_self(ia64_clock_xiv);
+#endif
 			hardclock(TRAPF_USERMODE(tf), TRAPF_PC(tf));
-		else
-			hardclock_cpu(TRAPF_USERMODE(tf));
+			if (profprocs != 0)
+				profclock(TRAPF_USERMODE(tf), TRAPF_PC(tf));
+			statclock(TRAPF_USERMODE(tf));
+			delta -= ia64_clock_reload;
+			clk += ia64_clock_reload;
+			if (adj != 0)
+				adjust_ticks++;
+			count++;
+		}
+		ia64_set_itm(ia64_get_itc() + ia64_clock_reload - adj);
+		ia64_srlz_d();
+		if (count > 0) {
+			adjust_lost += count - 1;
+			if (delta > (ia64_clock_reload >> 3)) {
+				if (adj == 0)
+					adjust_edges++;
+				adj = ia64_clock_reload >> 4;
+			} else
+				adj = 0;
+		} else {
+			adj = 0;
+			adjust_excess++;
+		}
+		PCPU_SET(md.clock, clk);
+		PCPU_SET(md.clockadj, adj);
+	} else {
+		/*
+		 * Clock processing on the BSP.
+		 */
+		hardclock_cpu(TRAPF_USERMODE(tf));
 		if (profprocs != 0)
 			profclock(TRAPF_USERMODE(tf), TRAPF_PC(tf));
 		statclock(TRAPF_USERMODE(tf));
-		delta -= ia64_clock_reload;
-		clk += ia64_clock_reload;
-		if (adj != 0)
-			adjust_ticks++;
-		count++;
-	}
-	ia64_set_itm(ia64_get_itc() + ia64_clock_reload - adj);
-	ia64_srlz_d();
-	if (count > 0) {
-		adjust_lost += count - 1;
-		if (delta > (ia64_clock_reload >> 3)) {
-			if (adj == 0)
-				adjust_edges++;
-			adj = ia64_clock_reload >> 4;
-		} else
-			adj = 0;
-	} else {
-		adj = 0;
-		adjust_excess++;
 	}
-	PCPU_SET(md.clock, clk);
-	PCPU_SET(md.clockadj, adj);
-	return (0);
-}
-
-void
-pcpu_initclock(void)
-{
 
-	PCPU_SET(md.clockadj, 0);
-	PCPU_SET(md.clock, ia64_get_itc());
-	ia64_set_itm(PCPU_GET(md.clock) + ia64_clock_reload);
-	ia64_set_itv(ia64_clock_xiv);
-	ia64_srlz_d();
+	return (0);
 }
 
 /*
@@ -154,7 +158,7 @@ cpu_initclocks()
 {
 	u_long itc_freq;
 
-	ia64_clock_xiv = ia64_xiv_alloc(PI_REALTIME, IA64_XIV_IRQ,
+	ia64_clock_xiv = ia64_xiv_alloc(PI_REALTIME, IA64_XIV_IPI,
 	    ia64_ih_clock);
 	if (ia64_clock_xiv == 0)
 		panic("No XIV for clock interrupts");
@@ -169,7 +173,11 @@ cpu_initclocks()
 	tc_init(&ia64_timecounter);
 #endif
 
-	pcpu_initclock();
+	PCPU_SET(md.clockadj, 0);
+	PCPU_SET(md.clock, ia64_get_itc());
+	ia64_set_itm(PCPU_GET(md.clock) + ia64_clock_reload);
+	ia64_set_itv(ia64_clock_xiv);
+	ia64_srlz_d();
 }
 
 void
diff --git a/sys/ia64/ia64/mp_machdep.c b/sys/ia64/ia64/mp_machdep.c
index 05a655d..f8d9f6f 100644
--- a/sys/ia64/ia64/mp_machdep.c
+++ b/sys/ia64/ia64/mp_machdep.c
@@ -206,9 +206,8 @@ ia64_ap_startup(void)
 
 	CTR1(KTR_SMP, "SMP: cpu%d launched", PCPU_GET(cpuid));
 
-	/* kick off the clock on this AP */
-	pcpu_initclock();
-
+	/* Mask interval timer interrupts on APs. */
+	ia64_set_itv(0x10000);
 	ia64_set_tpr(0);
 	ia64_srlz_d();
 	enable_intr();
diff --git a/sys/ia64/include/pcpu.h b/sys/ia64/include/pcpu.h
index 9eb8efb..3c6e6a7 100644
--- a/sys/ia64/include/pcpu.h
+++ b/sys/ia64/include/pcpu.h
@@ -91,8 +91,6 @@ __curthread(void)
 #define	PCPU_PTR(member)	(&pcpup->pc_ ## member)
 #define	PCPU_SET(member,value)	(pcpup->pc_ ## member = (value))
 
-void pcpu_initclock(void);
-
 #endif	/* _KERNEL */
 
 #endif	/* !_MACHINE_PCPU_H_ */