1 files changed, 200 insertions, 0 deletions
diff --git a/drivers/clocksource/hyperv_timer.c b/drivers/clocksource/hyperv_timer.c
new file mode 100644
index 000000000000..68a28af31561
--- /dev/null
+++ b/drivers/clocksource/hyperv_timer.c
@@ -0,0 +1,200 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/*
+ * Clocksource driver for the synthetic counter and timers
+ * provided by the Hyper-V hypervisor to guest VMs, as described
+ * in the Hyper-V Top Level Functional Spec (TLFS). This driver
+ * is instruction set architecture independent.
+ *
+ * Copyright (C) 2019, Microsoft, Inc.
+ *
+ * Author:  Michael Kelley <mikelley@microsoft.com>
+ */
+
+#include <linux/percpu.h>
+#include <linux/cpumask.h>
+#include <linux/clockchips.h>
+#include <linux/mm.h>
+#include <clocksource/hyperv_timer.h>
+#include <asm/hyperv-tlfs.h>
+#include <asm/mshyperv.h>
+
+static struct clock_event_device __percpu *hv_clock_event;
+
+/*
+ * If false, we're using the old mechanism for stimer0 interrupts
+ * where it sends a VMbus message when it expires. The old
+ * mechanism is used when running on older versions of Hyper-V
+ * that don't support Direct Mode. While Hyper-V provides
+ * four stimer's per CPU, Linux uses only stimer0.
+ */
+static bool direct_mode_enabled;
+
+static int stimer0_irq;
+static int stimer0_vector;
+static int stimer0_message_sint;
+
+/*
+ * ISR for when stimer0 is operating in Direct Mode.  Direct Mode
+ * does not use VMbus or any VMbus messages, so process here and not
+ * in the VMbus driver code.
+ */
+void hv_stimer0_isr(void)
+{
+	struct clock_event_device *ce;
+
+	ce = this_cpu_ptr(hv_clock_event);
+	ce->event_handler(ce);
+}
+EXPORT_SYMBOL_GPL(hv_stimer0_isr);
+
+static int hv_ce_set_next_event(unsigned long delta,
+				struct clock_event_device *evt)
+{
+	u64 current_tick;
+
+	current_tick = hyperv_cs->read(NULL);
+	current_tick += delta;
+	hv_init_timer(0, current_tick);
+	return 0;
+}
+
+static int hv_ce_shutdown(struct clock_event_device *evt)
+{
+	hv_init_timer(0, 0);
+	hv_init_timer_config(0, 0);
+	if (direct_mode_enabled)
+		hv_disable_stimer0_percpu_irq(stimer0_irq);
+
+	return 0;
+}
+
+static int hv_ce_set_oneshot(struct clock_event_device *evt)
+{
+	union hv_stimer_config timer_cfg;
+
+	timer_cfg.as_uint64 = 0;
+	timer_cfg.enable = 1;
+	timer_cfg.auto_enable = 1;
+	if (direct_mode_enabled) {
+		/*
+		 * When it expires, the timer will directly interrupt
+		 * on the specified hardware vector/IRQ.
+		 */
+		timer_cfg.direct_mode = 1;
+		timer_cfg.apic_vector = stimer0_vector;
+		hv_enable_stimer0_percpu_irq(stimer0_irq);
+	} else {
+		/*
+		 * When it expires, the timer will generate a VMbus message,
+		 * to be handled by the normal VMbus interrupt handler.
+		 */
+		timer_cfg.direct_mode = 0;
+		timer_cfg.sintx = stimer0_message_sint;
+	}
+	hv_init_timer_config(0, timer_cfg.as_uint64);
+	return 0;
+}
+
+/*
+ * hv_stimer_init - Per-cpu initialization of the clockevent
+ */
+void hv_stimer_init(unsigned int cpu)
+{
+	struct clock_event_device *ce;
+
+	/*
+	 * Synthetic timers are always available except on old versions of
+	 * Hyper-V on x86.  In that case, just return as Linux will use a
+	 * clocksource based on emulated PIT or LAPIC timer hardware.
+	 */
+	if (!(ms_hyperv.features & HV_MSR_SYNTIMER_AVAILABLE))
+		return;
+
+	ce = per_cpu_ptr(hv_clock_event, cpu);
+	ce->name = "Hyper-V clockevent";
+	ce->features = CLOCK_EVT_FEAT_ONESHOT;
+	ce->cpumask = cpumask_of(cpu);
+	ce->rating = 1000;
+	ce->set_state_shutdown = hv_ce_shutdown;
+	ce->set_state_oneshot = hv_ce_set_oneshot;
+	ce->set_next_event = hv_ce_set_next_event;
+
+	clockevents_config_and_register(ce,
+					HV_CLOCK_HZ,
+					HV_MIN_DELTA_TICKS,
+					HV_MAX_MAX_DELTA_TICKS);
+}
+EXPORT_SYMBOL_GPL(hv_stimer_init);
+
+/*
+ * hv_stimer_cleanup - Per-cpu cleanup of the clockevent
+ */
+void hv_stimer_cleanup(unsigned int cpu)
+{
+	struct clock_event_device *ce;
+
+	/* Turn off clockevent device */
+	if (ms_hyperv.features & HV_MSR_SYNTIMER_AVAILABLE) {
+		ce = per_cpu_ptr(hv_clock_event, cpu);
+		hv_ce_shutdown(ce);
+	}
+}
+EXPORT_SYMBOL_GPL(hv_stimer_cleanup);
+
+/* hv_stimer_alloc - Global initialization of the clockevent and stimer0 */
+int hv_stimer_alloc(int sint)
+{
+	int ret;
+
+	hv_clock_event = alloc_percpu(struct clock_event_device);
+	if (!hv_clock_event)
+		return -ENOMEM;
+
+	direct_mode_enabled = ms_hyperv.misc_features &
+			HV_STIMER_DIRECT_MODE_AVAILABLE;
+	if (direct_mode_enabled) {
+		ret = hv_setup_stimer0_irq(&stimer0_irq, &stimer0_vector,
+				hv_stimer0_isr);
+		if (ret) {
+			free_percpu(hv_clock_event);
+			hv_clock_event = NULL;
+			return ret;
+		}
+	}
+
+	stimer0_message_sint = sint;
+	return 0;
+}
+EXPORT_SYMBOL_GPL(hv_stimer_alloc);
+
+/* hv_stimer_free - Free global resources allocated by hv_stimer_alloc() */
+void hv_stimer_free(void)
+{
+	if (direct_mode_enabled && (stimer0_irq != 0)) {
+		hv_remove_stimer0_irq(stimer0_irq);
+		stimer0_irq = 0;
+	}
+	free_percpu(hv_clock_event);
+	hv_clock_event = NULL;
+}
+EXPORT_SYMBOL_GPL(hv_stimer_free);
+
+/*
+ * Do a global cleanup of clockevents for the cases of kexec and
+ * vmbus exit
+ */
+void hv_stimer_global_cleanup(void)
+{
+	int	cpu;
+	struct clock_event_device *ce;
+
+	if (ms_hyperv.features & HV_MSR_SYNTIMER_AVAILABLE) {
+		for_each_present_cpu(cpu) {
+			ce = per_cpu_ptr(hv_clock_event, cpu);
+			clockevents_unbind_device(ce, cpu);
+		}
+	}
+	hv_stimer_free();
+}
+EXPORT_SYMBOL_GPL(hv_stimer_global_cleanup);