drivers: clocksource: add CPU PM notifier for ARM architected timer

Few control settings done in architected timer as part of initialisation
can be lost when CPU enters deeper power states. They need to be
restored when the CPU is (warm)reset again.

This patch adds CPU PM notifiers to save the counter control register
when entering low power modes and restore it when CPU exits low power.

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Reviewed-by: Will Deacon <will.deacon@arm.com>
Acked-by: Olof Johansson <olof@lixom.net>
Signed-off-by: Sudeep KarkadaNagesha <sudeep.karkadanagesha@arm.com>
(cherry picked from commit 346e7480f1d4740b3d798da60f83f087ea6488b4)
Signed-off-by: Alex Shi <alex.shi@linaro.org>

diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c
index d8f7eecce10052ea3b898d22b01d64fcadf4e46f..958591e94f2aac7f16e7184ec8a3b6c777a47e54 100644 (file)
--- a/drivers/clocksource/arm_arch_timer.c
+++ b/drivers/clocksource/arm_arch_timer.c
@@ -13,6 +13,7 @@
 #include <linux/device.h>
 #include <linux/smp.h>
 #include <linux/cpu.h>
+#include <linux/cpu_pm.h>
 #include <linux/clockchips.h>
 #include <linux/interrupt.h>
 #include <linux/of_irq.h>
@@ -275,6 +276,33 @@ static struct notifier_block arch_timer_cpu_nb __cpuinitdata = {
        .notifier_call = arch_timer_cpu_notify,
 };
 
+#ifdef CONFIG_CPU_PM
+static unsigned int saved_cntkctl;
+static int arch_timer_cpu_pm_notify(struct notifier_block *self,
+                                   unsigned long action, void *hcpu)
+{
+       if (action == CPU_PM_ENTER)
+               saved_cntkctl = arch_timer_get_cntkctl();
+       else if (action == CPU_PM_ENTER_FAILED || action == CPU_PM_EXIT)
+               arch_timer_set_cntkctl(saved_cntkctl);
+       return NOTIFY_OK;
+}
+
+static struct notifier_block arch_timer_cpu_pm_notifier = {
+       .notifier_call = arch_timer_cpu_pm_notify,
+};
+
+static int __init arch_timer_cpu_pm_init(void)
+{
+       return cpu_pm_register_notifier(&arch_timer_cpu_pm_notifier);
+}
+#else
+static int __init arch_timer_cpu_pm_init(void)
+{
+       return 0;
+}
+#endif
+
 static int __init arch_timer_register(void)
 {
        int err;
@@ -324,11 +352,17 @@ static int __init arch_timer_register(void)
        if (err)
                goto out_free_irq;
 
+       err = arch_timer_cpu_pm_init();
+       if (err)
+               goto out_unreg_notify;
+
        /* Immediately configure the timer on the boot CPU */
        arch_timer_setup(this_cpu_ptr(arch_timer_evt));
 
        return 0;
 
+out_unreg_notify:
+       unregister_cpu_notifier(&arch_timer_cpu_nb);
 out_free_irq:
        if (arch_timer_use_virtual)
                free_percpu_irq(arch_timer_ppi[VIRT_PPI], arch_timer_evt);