CLOCKSOURCE: mips-gic: Update clockevent frequency on clock rate changes

This commit introduces the clockevent frequency update, using
a clock notifier. It will be used to support CPUFreq on platforms
using MIPS GIC based clockevents.

Signed-off-by: Ezequiel Garcia <[e-mail]>
Acked-by: Daniel Lezcano <[e-mail]>
Cc: [e-mail]
Cc: [e-mail]
Cc: [e-mail]
Cc: Thomas Gleixner <[e-mail]>
Cc: Andrew Bresticker <[e-mail]>
Cc: James Hartley <[e-mail]>
Cc: Govindraj Raja <[e-mail]>
Cc: Damien Horsley <[e-mail]>
Cc: James Hogan <[e-mail]>
Cc: Ezequiel Garcia <[e-mail]>
Patchwork: https://patchwork.linux-mips.org/patch/10782/
Signed-off-by: Ralf Baechle <[e-mail]>

drivers/clocksource/mips-gic-timer.c

···
 	disable_percpu_irq(gic_timer_irq);
 }
 
+static void gic_update_frequency(void *data)
+{
+	unsigned long rate = (unsigned long)data;
+
+	clockevents_update_freq(this_cpu_ptr(&gic_clockevent_device), rate);
+}
+
 static int gic_cpu_notifier(struct notifier_block *nb, unsigned long action,
 				void *data)
 {
···
 	return NOTIFY_OK;
 }
 
+static int gic_clk_notifier(struct notifier_block *nb, unsigned long action,
+			    void *data)
+{
+	struct clk_notifier_data *cnd = data;
+
+	if (action == POST_RATE_CHANGE)
+		on_each_cpu(gic_update_frequency, (void *)cnd->new_rate, 1);
+
+	return NOTIFY_OK;
+}
+
+
 static struct notifier_block gic_cpu_nb = {
 	.notifier_call = gic_cpu_notifier,
+};
+
+static struct notifier_block gic_clk_nb = {
+	.notifier_call = gic_clk_notifier,
 };
 
 static int gic_clockevent_init(void)
···
 static void __init gic_clocksource_of_init(struct device_node *node)
 {
 	struct clk *clk;
+	int ret;
 
 	if (WARN_ON(!gic_present || !node->parent ||
 		    !of_device_is_compatible(node->parent, "mti,gic")))
···
 	}
 
 	__gic_clocksource_init();
-	gic_clockevent_init();
+
+	ret = gic_clockevent_init();
+	if (!ret && !IS_ERR(clk)) {
+		if (clk_notifier_register(clk, &gic_clk_nb) < 0)
+			pr_warn("GIC: Unable to register clock notifier\n");
+	}
 
 	/* And finally start the counter */
 	gic_start_count();