Add clock interrupt support, adapted from the randomized dual clock

implementation from Dale Rahn but relicensed (with his permission)
under our standard ISC license.

6 files changed, 209 insertions, 28 deletions

diff --git a/sys/arch/powerpc64/conf/files.powerpc64 b/sys/arch/powerpc64/conf/files.powerpc64
index e54b7bd7bfa..24919fd4741 100644
--- a/sys/arch/powerpc64/conf/files.powerpc64
+++ b/sys/arch/powerpc64/conf/files.powerpc64
@@ -1,4 +1,4 @@
-# $OpenBSD: files.powerpc64,v 1.10 2020/06/10 15:10:51 kettenis Exp $
+# $OpenBSD: files.powerpc64,v 1.11 2020/06/10 19:06:53 kettenis Exp $
 
 maxpartitions	16
 maxusers	2 8 128
@@ -7,6 +7,7 @@ file	arch/powerpc64/powerpc64/locore.S
 file	arch/powerpc64/powerpc64/autoconf.c
 file	arch/powerpc64/powerpc64/bus_dma.c
 file	arch/powerpc64/powerpc64/bus_space.c
+file	arch/powerpc64/powerpc64/clock.c
 file	arch/powerpc64/powerpc64/conf.c
 file	arch/powerpc64/powerpc64/cpu.c
 file	arch/powerpc64/powerpc64/db_disasm.c		ddb
diff --git a/sys/arch/powerpc64/include/cpu.h b/sys/arch/powerpc64/include/cpu.h
index edabe01e045..51791d5fdde 100644
--- a/sys/arch/powerpc64/include/cpu.h
+++ b/sys/arch/powerpc64/include/cpu.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: cpu.h,v 1.8 2020/06/09 18:58:58 kettenis Exp $	*/
+/*	$OpenBSD: cpu.h,v 1.9 2020/06/10 19:06:53 kettenis Exp $	*/
 
 /*
  * Copyright (c) 2020 Mark Kettenis <kettenis@openbsd.org>
@@ -49,6 +49,12 @@ struct cpu_info {
 #define CPUSAVE_LEN	9
 	register_t	ci_tempsave[CPUSAVE_LEN];
 
+	uint64_t	ci_lasttb;
+	uint64_t	ci_nexttimerevent;
+	uint64_t	ci_nextstatevent;
+	int		ci_statspending;
+	
+	volatile int 	ci_cpl;
 	uint32_t	ci_ipending;
 #ifdef DIAGNOSTIC
 	int		ci_mutex_level;
diff --git a/sys/arch/powerpc64/powerpc64/clock.c b/sys/arch/powerpc64/powerpc64/clock.c
new file mode 100644
index 00000000000..2b1d1705972
--- /dev/null
+++ b/sys/arch/powerpc64/powerpc64/clock.c
@@ -0,0 +1,186 @@
+/*	$OpenBSD: clock.c,v 1.1 2020/06/10 19:06:53 kettenis Exp $	*/
+
+/*
+ * Copyright (c) 2020 Mark Kettenis <kettenis@openbsd.org>
+ * Copyright (c) 2003 Dale Rahn <drahn@openbsd.org>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include <sys/param.h>
+#include <sys/kernel.h>
+#include <sys/systm.h>
+#include <sys/evcount.h>
+#include <sys/timetc.h>
+
+#include <machine/cpufunc.h>
+
+extern uint64_t tb_freq;	/* cpu.c */
+
+uint64_t tick_increment;
+uint64_t statmin;
+uint32_t statvar;
+
+struct evcount clock_count;
+struct evcount stat_count;
+
+u_int	tb_get_timecount(struct timecounter *);
+
+static struct timecounter tb_timecounter = {
+	tb_get_timecount, NULL, 0x7fffffff, 0, "tb", 0, NULL
+};
+
+void	cpu_startclock(void);
+
+u_int
+tb_get_timecount(struct timecounter *tc)
+{
+	return mftb();
+}
+
+void
+cpu_initclocks(void)
+{
+	tick_increment = tb_freq / hz;
+
+	stathz = 100;
+	profhz = 1000; /* must be a multiple of stathz */
+
+	setstatclockrate(stathz);
+
+	evcount_attach(&clock_count, "clock", NULL);
+	evcount_attach(&stat_count, "stat", NULL);
+
+	cpu_startclock();
+
+	tb_timecounter.tc_frequency = tb_freq;
+	tc_init(&tb_timecounter);
+}
+
+void
+cpu_startclock(void)
+{
+	struct cpu_info *ci = curcpu();
+	uint64_t nextevent;
+
+	ci->ci_lasttb = mftb();
+	ci->ci_nexttimerevent = ci->ci_lasttb + tick_increment;
+	nextevent = ci->ci_nextstatevent = ci->ci_nexttimerevent;
+
+	mtdec(nextevent - ci->ci_lasttb);
+	intr_enable();
+}
+
+void
+decr_intr(struct trapframe *frame)
+{
+	struct cpu_info *ci = curcpu();
+	uint64_t tb, prevtb;
+	uint64_t nextevent;
+	uint32_t r;
+	int nstats;
+	int s;
+
+	/*
+	 * Based on the actual time delay since the last decrementer reload,
+	 * we arrange for earlier interrupt next time.
+	 */
+
+	tb = mftb();
+
+	while (ci->ci_nexttimerevent <= tb)
+		ci->ci_nexttimerevent += tick_increment;
+
+	prevtb = ci->ci_nexttimerevent - tick_increment;
+
+	for (nstats = 0; ci->ci_nextstatevent <= tb; nstats++) {
+		do {
+			r = random() & (statvar - 1);
+		} while (r == 0); /* random == 0 not allowed */
+		ci->ci_nextstatevent += statmin + r;
+	}
+	stat_count.ec_count += nstats;
+
+	if (ci->ci_nexttimerevent < ci->ci_nextstatevent)
+		nextevent = ci->ci_nexttimerevent;
+	else
+		nextevent = ci->ci_nextstatevent;
+
+	/* 
+	 * Transition of the MSB will trigger a decrementer interrupt.
+	 * So the next sequence is guaranteed to do the job without a
+	 * systematic skew.
+	 */
+	mtdec(nextevent - tb);
+	mtdec(nextevent - mftb());
+
+	if (ci->ci_cpl >= IPL_CLOCK) {
+		ci->ci_statspending += nstats;
+	} else {
+		nstats += ci->ci_statspending;
+		ci->ci_statspending = 0;
+
+		s = splclock();
+		intr_enable();
+
+		/*
+		 * Do standard timer interrupt stuff.
+		 */
+		while (ci->ci_lasttb < prevtb) {
+			ci->ci_lasttb += tick_increment;
+			clock_count.ec_count++;
+			hardclock((struct clockframe *)frame);
+		}
+
+		while (nstats-- > 0)
+			statclock((struct clockframe *)frame);
+
+		intr_disable();
+		splx(s);
+	}
+}
+
+void
+setstatclockrate(int newhz)
+{
+	uint64_t stat_increment;
+	uint64_t min_increment;
+	uint32_t var;
+	u_long msr;
+
+	msr = intr_disable();
+
+	stat_increment = tb_freq / newhz;
+	var = 0x40000000; /* really big power of two */
+	/* Find largest 2^n which is nearly smaller than statint/2. */
+	min_increment = stat_increment / 2 + 100;
+	while (var > min_increment)
+		var >>= 1;
+
+	/* Not atomic, but we can probably live with that. */
+	statmin = stat_increment - (var >> 1);
+	statvar = var;
+
+	intr_restore(msr);
+}
+
+void
+delay(u_int us)
+{
+	uint64_t tb;
+
+	tb = mftb();
+	tb += (us * tb_freq + 999999) / 1000000;
+	while (tb > mftb())
+		continue;
+}
diff --git a/sys/arch/powerpc64/powerpc64/cpu.c b/sys/arch/powerpc64/powerpc64/cpu.c
index e768f032323..26bdf0c0c7c 100644
--- a/sys/arch/powerpc64/powerpc64/cpu.c
+++ b/sys/arch/powerpc64/powerpc64/cpu.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: cpu.c,v 1.5 2020/06/07 20:50:24 kettenis Exp $	*/
+/*	$OpenBSD: cpu.c,v 1.6 2020/06/10 19:06:53 kettenis Exp $	*/
 
 /*
  * Copyright (c) 2020 Mark Kettenis <kettenis@openbsd.org>
@@ -77,14 +77,3 @@ cpu_attach(struct device *parent, struct device *dev, void *aux)
 	/* Update timebase frequency to reflect reality. */
 	tb_freq = OF_getpropint(faa->fa_node, "timebase-frequency", tb_freq);
 }
-
-void
-delay(u_int us)
-{
-	uint64_t tb;
-
-	tb = mftb();
-	tb += (us * tb_freq + 999999) / 1000000;
-	while (tb > mftb())
-		continue;
-}
diff --git a/sys/arch/powerpc64/powerpc64/machdep.c b/sys/arch/powerpc64/powerpc64/machdep.c
index 91878121606..3e086fc0af8 100644
--- a/sys/arch/powerpc64/powerpc64/machdep.c
+++ b/sys/arch/powerpc64/powerpc64/machdep.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: machdep.c,v 1.18 2020/06/08 18:37:16 kettenis Exp $	*/
+/*	$OpenBSD: machdep.c,v 1.19 2020/06/10 19:06:53 kettenis Exp $	*/
 
 /*
  * Copyright (c) 2020 Mark Kettenis <kettenis@openbsd.org>
@@ -444,18 +444,6 @@ cpu_startup(void)
 }
 
 void
-cpu_initclocks(void)
-{
-	printf("%s\n", __func__);
-}
-
-void
-setstatclockrate(int new)
-{
-	printf("%s\n", __func__);
-}
-
-void
 setregs(struct proc *p, struct exec_package *pack, u_long stack,
     register_t *retval)
 {
diff --git a/sys/arch/powerpc64/powerpc64/trap.c b/sys/arch/powerpc64/powerpc64/trap.c
index 7f37d556d7c..07f8020c5d7 100644
--- a/sys/arch/powerpc64/powerpc64/trap.c
+++ b/sys/arch/powerpc64/powerpc64/trap.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: trap.c,v 1.3 2020/05/27 22:22:04 gkoehler Exp $	*/
+/*	$OpenBSD: trap.c,v 1.4 2020/06/10 19:06:53 kettenis Exp $	*/
 
 /*
  * Copyright (c) 2020 Mark Kettenis <kettenis@openbsd.org>
@@ -24,9 +24,17 @@
 #endif
 #include <machine/trap.h>
 
+void	decr_intr(struct trapframe *); /* clock.c */
+
 void
 trap(struct trapframe *frame)
 {
+	switch (frame->exc) {
+	case EXC_DECR:
+		decr_intr(frame);
+		return;
+	}
+
 #ifdef DDB
 	/* At a trap instruction, enter the debugger. */
 	if (frame->exc == EXC_PGM && (frame->srr1 & EXC_PGM_TRAP)) {
@@ -36,5 +44,8 @@ trap(struct trapframe *frame)
 	}
 #endif
 
+	if (frame->exc == EXC_DSI)
+		printf("dsisr %lx dar %lx\n", frame->dsisr, frame->dar);
+
 	panic("trap type %lx at lr %lx", frame->exc, frame->lr);
 }