clocksource: mips-gic: Use CPU notifiers to setup the timer

Instead of requiring an explicit call to gic_clockevent_init in the SMP
startup path, use CPU notifiers to register and enable the GIC timer on
CPU startup.
Signed-off-by: Andrew Bresticker <abrestic@chromium.org>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Jason Cooper <jason@lakedaemon.net>
Cc: Paul Burton <paul.burton@imgtec.com>
Cc: Qais Yousef <qais.yousef@imgtec.com>
Cc: John Crispin <blogic@openwrt.org>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/8139/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/include/asm/time.h

@@ -53,13 +53,10 @@ extern int __weak get_c0_perfcount_int(void);
  */
 extern unsigned int __weak get_c0_compare_int(void);
 extern int r4k_clockevent_init(void);
-extern int gic_clockevent_init(void);
 
 static inline int mips_clockevent_init(void)
 {
-#if   defined(CONFIG_CLKSRC_MIPS_GIC)
-	return (gic_clockevent_init() | r4k_clockevent_init());
-#elif defined(CONFIG_CEVT_R4K)
+#ifdef CONFIG_CEVT_R4K
 	return r4k_clockevent_init();
 #else
 	return -ENXIO;

drivers/clocksource/mips-gic-timer.c

@@ -6,9 +6,11 @@
  * Copyright (C) 2012 MIPS Technologies, Inc.  All rights reserved.
  */
 #include <linux/clockchips.h>
+#include <linux/cpu.h>
 #include <linux/init.h>
 #include <linux/interrupt.h>
 #include <linux/irqchip/mips-gic.h>
+#include <linux/notifier.h>
 #include <linux/percpu.h>
 #include <linux/smp.h>
 #include <linux/time.h>
@@ -16,7 +18,7 @@
 #include <asm/time.h>
 
 static DEFINE_PER_CPU(struct clock_event_device, gic_clockevent_device);
-static int gic_timer_irq_installed;
+static int gic_timer_irq;
 static unsigned int gic_frequency;
 
 static int gic_next_event(unsigned long delta, struct clock_event_device *evt)
@@ -53,18 +55,9 @@ struct irqaction gic_compare_irqaction = {
 	.name = "timer",
 };
 
-int gic_clockevent_init(void)
+static void gic_clockevent_cpu_init(struct clock_event_device *cd)
 {
 	unsigned int cpu = smp_processor_id();
-	struct clock_event_device *cd;
-	unsigned int irq;
-
-	if (!cpu_has_counter || !gic_frequency)
-		return -ENXIO;
-
-	irq = MIPS_GIC_IRQ_BASE + GIC_LOCAL_TO_HWIRQ(GIC_LOCAL_INT_COMPARE);
-
-	cd = &per_cpu(gic_clockevent_device, cpu);
 
 	cd->name		= "MIPS GIC";
 	cd->features		= CLOCK_EVT_FEAT_ONESHOT |
@@ -77,19 +70,52 @@ int gic_clockevent_init(void)
 	cd->min_delta_ns	= clockevent_delta2ns(0x300, cd);
 
 	cd->rating		= 300;
-	cd->irq			= irq;
+	cd->irq			= gic_timer_irq;
 	cd->cpumask		= cpumask_of(cpu);
 	cd->set_next_event	= gic_next_event;
 	cd->set_mode		= gic_set_clock_mode;
 
 	clockevents_register_device(cd);
 
-	if (!gic_timer_irq_installed) {
-		setup_percpu_irq(irq, &gic_compare_irqaction);
-		gic_timer_irq_installed = 1;
+	enable_percpu_irq(gic_timer_irq, IRQ_TYPE_NONE);
+}
+
+static void gic_clockevent_cpu_exit(struct clock_event_device *cd)
+{
+	disable_percpu_irq(gic_timer_irq);
+}
+
+static int gic_cpu_notifier(struct notifier_block *nb, unsigned long action,
+				void *data)
+{
+	switch (action & ~CPU_TASKS_FROZEN) {
+	case CPU_STARTING:
+		gic_clockevent_cpu_init(this_cpu_ptr(&gic_clockevent_device));
+		break;
+	case CPU_DYING:
+		gic_clockevent_cpu_exit(this_cpu_ptr(&gic_clockevent_device));
+		break;
 	}
 
-	enable_percpu_irq(irq, IRQ_TYPE_NONE);
+	return NOTIFY_OK;
+}
+
+static struct notifier_block gic_cpu_nb = {
+	.notifier_call = gic_cpu_notifier,
+};
+
+static int gic_clockevent_init(void)
+{
+	if (!cpu_has_counter || !gic_frequency)
+		return -ENXIO;
+
+	gic_timer_irq = MIPS_GIC_IRQ_BASE +
+		GIC_LOCAL_TO_HWIRQ(GIC_LOCAL_INT_COMPARE);
+	setup_percpu_irq(gic_timer_irq, &gic_compare_irqaction);
+
+	register_cpu_notifier(&gic_cpu_nb);
+
+	gic_clockevent_cpu_init(this_cpu_ptr(&gic_clockevent_device));
 
 	return 0;
 }
@@ -116,4 +142,6 @@ void __init gic_clocksource_init(unsigned int frequency)
 	gic_clocksource.rating = 200 + frequency / 10000000;
 
 	clocksource_register_hz(&gic_clocksource, frequency);
+
+	gic_clockevent_init();
 }