clocksource: time-armada-370-xp: add suspend/resume support

This commit adds a set of suspend/resume syscore_ops to respectively
save and restore a number of timer registers, in order to make sure
the clockevent and clocksource devices continue to work properly
across a suspend/resume cycle.
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lkml.kernel.org/r/1416585613-2113-5-git-send-email-thomas.petazzoni@free-electrons.comSigned-off-by: Jason Cooper <jason@lakedaemon.net>

drivers/clocksource/time-armada-370-xp.c

@@ -43,6 +43,7 @@
 #include <linux/module.h>
 #include <linux/sched_clock.h>
 #include <linux/percpu.h>
+#include <linux/syscore_ops.h>
 
 /*
  * Timer block registers.
@@ -223,6 +224,28 @@ static struct notifier_block armada_370_xp_timer_cpu_nb = {
 	.notifier_call = armada_370_xp_timer_cpu_notify,
 };
 
+static u32 timer0_ctrl_reg, timer0_local_ctrl_reg;
+
+static int armada_370_xp_timer_suspend(void)
+{
+	timer0_ctrl_reg = readl(timer_base + TIMER_CTRL_OFF);
+	timer0_local_ctrl_reg = readl(local_base + TIMER_CTRL_OFF);
+	return 0;
+}
+
+static void armada_370_xp_timer_resume(void)
+{
+	writel(0xffffffff, timer_base + TIMER0_VAL_OFF);
+	writel(0xffffffff, timer_base + TIMER0_RELOAD_OFF);
+	writel(timer0_ctrl_reg, timer_base + TIMER_CTRL_OFF);
+	writel(timer0_local_ctrl_reg, local_base + TIMER_CTRL_OFF);
+}
+
+struct syscore_ops armada_370_xp_timer_syscore_ops = {
+	.suspend	= armada_370_xp_timer_suspend,
+	.resume		= armada_370_xp_timer_resume,
+};
+
 static void __init armada_370_xp_timer_common_init(struct device_node *np)
 {
 	u32 clr = 0, set = 0;
@@ -285,6 +308,8 @@ static void __init armada_370_xp_timer_common_init(struct device_node *np)
 	/* Immediately configure the timer on the boot CPU */
 	if (!res)
 		armada_370_xp_timer_setup(this_cpu_ptr(armada_370_xp_evt));
+
+	register_syscore_ops(&armada_370_xp_timer_syscore_ops);
 }
 
 static void __init armada_xp_timer_init(struct device_node *np)