1 files changed, 172 insertions, 0 deletions
diff --git a/arch/openrisc/kernel/time.c b/arch/openrisc/kernel/time.c
new file mode 100644
index 000000000..b82866061
--- /dev/null
+++ b/arch/openrisc/kernel/time.c
@@ -0,0 +1,172 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * OpenRISC time.c
+ *
+ * Linux architectural port borrowing liberally from similar works of
+ * others.  All original copyrights apply as per the original source
+ * declaration.
+ *
+ * Modifications for the OpenRISC architecture:
+ * Copyright (C) 2010-2011 Jonas Bonn <jonas@southpole.se>
+ */
+
+#include <linux/kernel.h>
+#include <linux/time.h>
+#include <linux/timex.h>
+#include <linux/interrupt.h>
+#include <linux/ftrace.h>
+
+#include <linux/clocksource.h>
+#include <linux/clockchips.h>
+#include <linux/irq.h>
+#include <linux/io.h>
+
+#include <asm/cpuinfo.h>
+
+/* Test the timer ticks to count, used in sync routine */
+inline void openrisc_timer_set(unsigned long count)
+{
+	mtspr(SPR_TTCR, count);
+}
+
+/* Set the timer to trigger in delta cycles */
+inline void openrisc_timer_set_next(unsigned long delta)
+{
+	u32 c;
+
+	/* Read 32-bit counter value, add delta, mask off the low 28 bits.
+	 * We're guaranteed delta won't be bigger than 28 bits because the
+	 * generic timekeeping code ensures that for us.
+	 */
+	c = mfspr(SPR_TTCR);
+	c += delta;
+	c &= SPR_TTMR_TP;
+
+	/* Set counter and enable interrupt.
+	 * Keep timer in continuous mode always.
+	 */
+	mtspr(SPR_TTMR, SPR_TTMR_CR | SPR_TTMR_IE | c);
+}
+
+static int openrisc_timer_set_next_event(unsigned long delta,
+					 struct clock_event_device *dev)
+{
+	openrisc_timer_set_next(delta);
+	return 0;
+}
+
+/* This is the clock event device based on the OR1K tick timer.
+ * As the timer is being used as a continuous clock-source (required for HR
+ * timers) we cannot enable the PERIODIC feature.  The tick timer can run using
+ * one-shot events, so no problem.
+ */
+DEFINE_PER_CPU(struct clock_event_device, clockevent_openrisc_timer);
+
+void openrisc_clockevent_init(void)
+{
+	unsigned int cpu = smp_processor_id();
+	struct clock_event_device *evt =
+		&per_cpu(clockevent_openrisc_timer, cpu);
+	struct cpuinfo_or1k *cpuinfo = &cpuinfo_or1k[cpu];
+
+	mtspr(SPR_TTMR, SPR_TTMR_CR);
+
+#ifdef CONFIG_SMP
+	evt->broadcast = tick_broadcast;
+#endif
+	evt->name = "openrisc_timer_clockevent",
+	evt->features = CLOCK_EVT_FEAT_ONESHOT,
+	evt->rating = 300,
+	evt->set_next_event = openrisc_timer_set_next_event,
+
+	evt->cpumask = cpumask_of(cpu);
+
+	/* We only have 28 bits */
+	clockevents_config_and_register(evt, cpuinfo->clock_frequency,
+					100, 0x0fffffff);
+
+}
+
+static inline void timer_ack(void)
+{
+	/* Clear the IP bit and disable further interrupts */
+	/* This can be done very simply... we just need to keep the timer
+	   running, so just maintain the CR bits while clearing the rest
+	   of the register
+	 */
+	mtspr(SPR_TTMR, SPR_TTMR_CR);
+}
+
+/*
+ * The timer interrupt is mostly handled in generic code nowadays... this
+ * function just acknowledges the interrupt and fires the event handler that
+ * has been set on the clockevent device by the generic time management code.
+ *
+ * This function needs to be called by the timer exception handler and that's
+ * all the exception handler needs to do.
+ */
+
+irqreturn_t __irq_entry timer_interrupt(struct pt_regs *regs)
+{
+	struct pt_regs *old_regs = set_irq_regs(regs);
+	unsigned int cpu = smp_processor_id();
+	struct clock_event_device *evt =
+		&per_cpu(clockevent_openrisc_timer, cpu);
+
+	timer_ack();
+
+	/*
+	 * update_process_times() expects us to have called irq_enter().
+	 */
+	irq_enter();
+	evt->event_handler(evt);
+	irq_exit();
+
+	set_irq_regs(old_regs);
+
+	return IRQ_HANDLED;
+}
+
+/**
+ * Clocksource: Based on OpenRISC timer/counter
+ *
+ * This sets up the OpenRISC Tick Timer as a clock source.  The tick timer
+ * is 32 bits wide and runs at the CPU clock frequency.
+ */
+static u64 openrisc_timer_read(struct clocksource *cs)
+{
+	return (u64) mfspr(SPR_TTCR);
+}
+
+static struct clocksource openrisc_timer = {
+	.name = "openrisc_timer",
+	.rating = 200,
+	.read = openrisc_timer_read,
+	.mask = CLOCKSOURCE_MASK(32),
+	.flags = CLOCK_SOURCE_IS_CONTINUOUS,
+};
+
+static int __init openrisc_timer_init(void)
+{
+	struct cpuinfo_or1k *cpuinfo = &cpuinfo_or1k[smp_processor_id()];
+
+	if (clocksource_register_hz(&openrisc_timer, cpuinfo->clock_frequency))
+		panic("failed to register clocksource");
+
+	/* Enable the incrementer: 'continuous' mode with interrupt disabled */
+	mtspr(SPR_TTMR, SPR_TTMR_CR);
+
+	return 0;
+}
+
+void __init time_init(void)
+{
+	u32 upr;
+
+	upr = mfspr(SPR_UPR);
+	if (!(upr & SPR_UPR_TTP))
+		panic("Linux not supported on devices without tick timer");
+
+	openrisc_timer_init();
+	openrisc_clockevent_init();
+}