Initial Spring 2016 commit.

kern/dev/lamebus/ltimer.c

@@ -0,0 +1,187 @@
+/*
+ * Copyright (c) 2000, 2001, 2002, 2003, 2004, 2005, 2008, 2009
+ *	The President and Fellows of Harvard College.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the University nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE UNIVERSITY AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE UNIVERSITY OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+/*
+ * Driver for LAMEbus clock/timer card
+ */
+#include <types.h>
+#include <lib.h>
+#include <spl.h>
+#include <clock.h>
+#include <platform/bus.h>
+#include <lamebus/ltimer.h>
+#include "autoconf.h"
+
+/* Registers (offsets within slot) */
+#define LT_REG_SEC    0     /* time of day: seconds */
+#define LT_REG_NSEC   4     /* time of day: nanoseconds */
+#define LT_REG_ROE    8     /* Restart On countdown-timer Expiry flag */
+#define LT_REG_IRQ    12    /* Interrupt status register */
+#define LT_REG_COUNT  16    /* Time for countdown timer (usec) */
+#define LT_REG_SPKR   20    /* Beep control */
+
+/* Granularity of countdown timer (usec) */
+#define LT_GRANULARITY   1000000
+
+static bool havetimerclock;
+
+/*
+ * Setup routine called by autoconf stuff when an ltimer is found.
+ */
+int
+config_ltimer(struct ltimer_softc *lt, int ltimerno)
+{
+	/*
+	 * Running on System/161 2.x, we always use the processor
+	 * on-chip timer for hardclock and we don't need ltimer as
+	 * hardclock.
+	 *
+	 * Ideally there should be code here that will use an ltimer
+	 * for hardclock if nothing else is available; e.g. if we
+	 * wanted to make OS/161 2.x run on System/161 1.x. However,
+	 * that requires a good bit more infrastructure for handling
+	 * timers than we have and it doesn't seem worthwhile.
+	 *
+	 * It would also require some hacking, because all CPUs need
+	 * to receive timer interrupts. (Exercise: how would you make
+	 * sure all CPUs receive exactly one timer interrupt? Remember
+	 * that LAMEbus uses level-triggered interrupts, so the
+	 * hardware interrupt line will cause repeated interrupts if
+	 * it's not reset on the device; but if it's reset on the
+	 * device before all CPUs manage to see it, those CPUs won't
+	 * be interrupted at all.)
+	 *
+	 * Note that the beep and rtclock devices *do* attach to
+	 * ltimer.
+	 */
+	(void)ltimerno;
+	lt->lt_hardclock = 0;
+
+	/*
+	 * We do, however, use ltimer for the timer clock, since the
+	 * on-chip timer can't do that.
+	 */
+	if (!havetimerclock) {
+		havetimerclock = true;
+		lt->lt_timerclock = 1;
+
+		/* Wire it to go off once every second. */
+		bus_write_register(lt->lt_bus, lt->lt_buspos, LT_REG_ROE, 1);
+		bus_write_register(lt->lt_bus, lt->lt_buspos, LT_REG_COUNT,
+				   LT_GRANULARITY);
+	}
+
+	return 0;
+}
+
+/*
+ * Interrupt handler.
+ */
+void
+ltimer_irq(void *vlt)
+{
+	struct ltimer_softc *lt = vlt;
+	uint32_t val;
+
+	val = bus_read_register(lt->lt_bus, lt->lt_buspos, LT_REG_IRQ);
+	if (val) {
+		/*
+		 * Only call hardclock if we're responsible for hardclock.
+		 * (Any additional timer devices are unused.)
+		 */
+		if (lt->lt_hardclock) {
+			hardclock();
+		}
+		/*
+		 * Likewise for timerclock.
+		 */
+		if (lt->lt_timerclock) {
+			timerclock();
+		}
+	}
+}
+
+/*
+ * The timer device will beep if you write to the beep register. It
+ * doesn't matter what value you write. This function is called if
+ * the beep device is attached to this timer.
+ */
+void
+ltimer_beep(void *vlt)
+{
+	struct ltimer_softc *lt = vlt;
+
+	bus_write_register(lt->lt_bus, lt->lt_buspos, LT_REG_SPKR, 440);
+}
+
+/*
+ * The timer device also has a realtime clock on it.
+ * This function gets called if the rtclock device is attached
+ * to this timer.
+ */
+void
+ltimer_gettime(void *vlt, struct timespec *ts)
+{
+	struct ltimer_softc *lt = vlt;
+	uint32_t secs1, secs2;
+	int spl;
+
+	/*
+	 * Read the seconds twice, on either side of the nanoseconds.
+	 * If nsecs is small, use the *later* value of seconds, in case
+	 * the nanoseconds turned over between the time we got the earlier
+	 * value and the time we got nsecs.
+	 *
+	 * Note that the clock in the ltimer device is accurate down
+	 * to a single processor cycle, so this might actually matter
+	 * now and then.
+	 *
+	 * Do it with interrupts off on the current processor to avoid
+	 * getting garbage if we get an interrupt among the register
+	 * reads.
+	 */
+
+	spl = splhigh();
+
+	secs1 = bus_read_register(lt->lt_bus, lt->lt_buspos,
+				  LT_REG_SEC);
+	ts->tv_nsec = bus_read_register(lt->lt_bus, lt->lt_buspos,
+				   LT_REG_NSEC);
+	secs2 = bus_read_register(lt->lt_bus, lt->lt_buspos,
+				  LT_REG_SEC);
+
+	splx(spl);
+
+	if (ts->tv_nsec < 5000000) {
+		ts->tv_sec = secs2;
+	}
+	else {
+		ts->tv_sec = secs1;
+	}
+}