1 files changed, 269 insertions, 0 deletions
diff --git a/arch/parisc/kernel/time.c b/arch/parisc/kernel/time.c
new file mode 100644
index 000000000..9714fbd7c
--- /dev/null
+++ b/arch/parisc/kernel/time.c
@@ -0,0 +1,269 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ *  linux/arch/parisc/kernel/time.c
+ *
+ *  Copyright (C) 1991, 1992, 1995  Linus Torvalds
+ *  Modifications for ARM (C) 1994, 1995, 1996,1997 Russell King
+ *  Copyright (C) 1999 SuSE GmbH, (Philipp Rumpf, prumpf@tux.org)
+ *
+ * 1994-07-02  Alan Modra
+ *             fixed set_rtc_mmss, fixed time.year for >= 2000, new mktime
+ * 1998-12-20  Updated NTP code according to technical memorandum Jan '96
+ *             "A Kernel Model for Precision Timekeeping" by Dave Mills
+ */
+#include <linux/errno.h>
+#include <linux/module.h>
+#include <linux/rtc.h>
+#include <linux/sched.h>
+#include <linux/sched/clock.h>
+#include <linux/sched_clock.h>
+#include <linux/kernel.h>
+#include <linux/param.h>
+#include <linux/string.h>
+#include <linux/mm.h>
+#include <linux/interrupt.h>
+#include <linux/time.h>
+#include <linux/init.h>
+#include <linux/smp.h>
+#include <linux/profile.h>
+#include <linux/clocksource.h>
+#include <linux/platform_device.h>
+#include <linux/ftrace.h>
+
+#include <linux/uaccess.h>
+#include <asm/io.h>
+#include <asm/irq.h>
+#include <asm/page.h>
+#include <asm/param.h>
+#include <asm/pdc.h>
+#include <asm/led.h>
+
+#include <linux/timex.h>
+
+int time_keeper_id __read_mostly;	/* CPU used for timekeeping. */
+
+static unsigned long clocktick __ro_after_init;	/* timer cycles per tick */
+
+/*
+ * We keep time on PA-RISC Linux by using the Interval Timer which is
+ * a pair of registers; one is read-only and one is write-only; both
+ * accessed through CR16.  The read-only register is 32 or 64 bits wide,
+ * and increments by 1 every CPU clock tick.  The architecture only
+ * guarantees us a rate between 0.5 and 2, but all implementations use a
+ * rate of 1.  The write-only register is 32-bits wide.  When the lowest
+ * 32 bits of the read-only register compare equal to the write-only
+ * register, it raises a maskable external interrupt.  Each processor has
+ * an Interval Timer of its own and they are not synchronised.  
+ *
+ * We want to generate an interrupt every 1/HZ seconds.  So we program
+ * CR16 to interrupt every @clocktick cycles.  The it_value in cpu_data
+ * is programmed with the intended time of the next tick.  We can be
+ * held off for an arbitrarily long period of time by interrupts being
+ * disabled, so we may miss one or more ticks.
+ */
+irqreturn_t __irq_entry timer_interrupt(int irq, void *dev_id)
+{
+	unsigned long now;
+	unsigned long next_tick;
+	unsigned long ticks_elapsed = 0;
+	unsigned int cpu = smp_processor_id();
+	struct cpuinfo_parisc *cpuinfo = &per_cpu(cpu_data, cpu);
+
+	/* gcc can optimize for "read-only" case with a local clocktick */
+	unsigned long cpt = clocktick;
+
+	/* Initialize next_tick to the old expected tick time. */
+	next_tick = cpuinfo->it_value;
+
+	/* Calculate how many ticks have elapsed. */
+	now = mfctl(16);
+	do {
+		++ticks_elapsed;
+		next_tick += cpt;
+	} while (next_tick - now > cpt);
+
+	/* Store (in CR16 cycles) up to when we are accounting right now. */
+	cpuinfo->it_value = next_tick;
+
+	/* Go do system house keeping. */
+	if (IS_ENABLED(CONFIG_SMP) && (cpu != time_keeper_id))
+		ticks_elapsed = 0;
+	legacy_timer_tick(ticks_elapsed);
+
+	/* Skip clockticks on purpose if we know we would miss those.
+	 * The new CR16 must be "later" than current CR16 otherwise
+	 * itimer would not fire until CR16 wrapped - e.g 4 seconds
+	 * later on a 1Ghz processor. We'll account for the missed
+	 * ticks on the next timer interrupt.
+	 * We want IT to fire modulo clocktick even if we miss/skip some.
+	 * But those interrupts don't in fact get delivered that regularly.
+	 *
+	 * "next_tick - now" will always give the difference regardless
+	 * if one or the other wrapped. If "now" is "bigger" we'll end up
+	 * with a very large unsigned number.
+	 */
+	now = mfctl(16);
+	while (next_tick - now > cpt)
+		next_tick += cpt;
+
+	/* Program the IT when to deliver the next interrupt.
+	 * Only bottom 32-bits of next_tick are writable in CR16!
+	 * Timer interrupt will be delivered at least a few hundred cycles
+	 * after the IT fires, so if we are too close (<= 8000 cycles) to the
+	 * next cycle, simply skip it.
+	 */
+	if (next_tick - now <= 8000)
+		next_tick += cpt;
+	mtctl(next_tick, 16);
+
+	return IRQ_HANDLED;
+}
+
+
+unsigned long profile_pc(struct pt_regs *regs)
+{
+	unsigned long pc = instruction_pointer(regs);
+
+	if (regs->gr[0] & PSW_N)
+		pc -= 4;
+
+#ifdef CONFIG_SMP
+	if (in_lock_functions(pc))
+		pc = regs->gr[2];
+#endif
+
+	return pc;
+}
+EXPORT_SYMBOL(profile_pc);
+
+
+/* clock source code */
+
+static u64 notrace read_cr16(struct clocksource *cs)
+{
+	return get_cycles();
+}
+
+static struct clocksource clocksource_cr16 = {
+	.name			= "cr16",
+	.rating			= 300,
+	.read			= read_cr16,
+	.mask			= CLOCKSOURCE_MASK(BITS_PER_LONG),
+	.flags			= CLOCK_SOURCE_IS_CONTINUOUS,
+};
+
+void start_cpu_itimer(void)
+{
+	unsigned int cpu = smp_processor_id();
+	unsigned long next_tick = mfctl(16) + clocktick;
+
+	mtctl(next_tick, 16);		/* kick off Interval Timer (CR16) */
+
+	per_cpu(cpu_data, cpu).it_value = next_tick;
+}
+
+#if IS_ENABLED(CONFIG_RTC_DRV_GENERIC)
+static int rtc_generic_get_time(struct device *dev, struct rtc_time *tm)
+{
+	struct pdc_tod tod_data;
+
+	memset(tm, 0, sizeof(*tm));
+	if (pdc_tod_read(&tod_data) < 0)
+		return -EOPNOTSUPP;
+
+	/* we treat tod_sec as unsigned, so this can work until year 2106 */
+	rtc_time64_to_tm(tod_data.tod_sec, tm);
+	return 0;
+}
+
+static int rtc_generic_set_time(struct device *dev, struct rtc_time *tm)
+{
+	time64_t secs = rtc_tm_to_time64(tm);
+	int ret;
+
+	/* hppa has Y2K38 problem: pdc_tod_set() takes an u32 value! */
+	ret = pdc_tod_set(secs, 0);
+	if (ret != 0) {
+		pr_warn("pdc_tod_set(%lld) returned error %d\n", secs, ret);
+		if (ret == PDC_INVALID_ARG)
+			return -EINVAL;
+		return -EOPNOTSUPP;
+	}
+
+	return 0;
+}
+
+static const struct rtc_class_ops rtc_generic_ops = {
+	.read_time = rtc_generic_get_time,
+	.set_time = rtc_generic_set_time,
+};
+
+static int __init rtc_init(void)
+{
+	struct platform_device *pdev;
+
+	pdev = platform_device_register_data(NULL, "rtc-generic", -1,
+					     &rtc_generic_ops,
+					     sizeof(rtc_generic_ops));
+
+	return PTR_ERR_OR_ZERO(pdev);
+}
+device_initcall(rtc_init);
+#endif
+
+void read_persistent_clock64(struct timespec64 *ts)
+{
+	static struct pdc_tod tod_data;
+	if (pdc_tod_read(&tod_data) == 0) {
+		ts->tv_sec = tod_data.tod_sec;
+		ts->tv_nsec = tod_data.tod_usec * 1000;
+	} else {
+		printk(KERN_ERR "Error reading tod clock\n");
+	        ts->tv_sec = 0;
+		ts->tv_nsec = 0;
+	}
+}
+
+
+static u64 notrace read_cr16_sched_clock(void)
+{
+	return get_cycles();
+}
+
+
+/*
+ * timer interrupt and sched_clock() initialization
+ */
+
+void __init time_init(void)
+{
+	unsigned long cr16_hz;
+
+	clocktick = (100 * PAGE0->mem_10msec) / HZ;
+	start_cpu_itimer();	/* get CPU 0 started */
+
+	cr16_hz = 100 * PAGE0->mem_10msec;  /* Hz */
+
+	/* register as sched_clock source */
+	sched_clock_register(read_cr16_sched_clock, BITS_PER_LONG, cr16_hz);
+}
+
+static int __init init_cr16_clocksource(void)
+{
+	/*
+	 * The cr16 interval timers are not synchronized across CPUs.
+	 */
+	if (num_online_cpus() > 1 && !running_on_qemu) {
+		clocksource_cr16.name = "cr16_unstable";
+		clocksource_cr16.flags = CLOCK_SOURCE_UNSTABLE;
+		clocksource_cr16.rating = 0;
+	}
+
+	/* register at clocksource framework */
+	clocksource_register_hz(&clocksource_cr16,
+		100 * PAGE0->mem_10msec);
+
+	return 0;
+}
+
+device_initcall(init_cr16_clocksource);