2 files changed, 64 insertions, 0 deletions

diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
index 971d796e071d..5e940f839a2d 100644
--- a/drivers/clocksource/Kconfig
+++ b/drivers/clocksource/Kconfig
@@ -75,6 +75,21 @@ config ARM_ARCH_TIMER
         bool
         select CLKSRC_OF if OF
 
+config ARM_ARCH_TIMER_EVTSTREAM
+        bool "Support for ARM architected timer event stream generation"
+        default y if ARM_ARCH_TIMER
+        help
+          This option enables support for event stream generation based on
+          the ARM architected timer. It is used for waking up CPUs executing
+          the wfe instruction at a frequency represented as a power-of-2
+          divisor of the clock rate.
+          The main use of the event stream is wfe-based timeouts of userspace
+          locking implementations. It might also be useful for imposing timeout
+          on wfe to safeguard against any programming errors in case an expected
+          event is not generated.
+          This must be disabled for hardware validation purposes to detect any
+          hardware anomalies of missing events.
+
 config ARM_GLOBAL_TIMER
         bool
         select CLKSRC_OF if OF
diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c
index ce98d5e70927..b94b0d44c158 100644
--- 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>
@@ -294,6 +295,19 @@ static void __arch_timer_setup(unsigned type,
         clockevents_config_and_register(clk, arch_timer_rate, 0xf, 0x7fffffff);
 }
 
+static void arch_timer_configure_evtstream(void)
+{
+        int evt_stream_div, pos;
+
+        /* Find the closest power of two to the divisor */
+        evt_stream_div = arch_timer_rate / ARCH_TIMER_EVT_STREAM_FREQ;
+        pos = fls(evt_stream_div);
+        if (pos > 1 && !(evt_stream_div & (1 << (pos - 2))))
+                pos--;
+        /* enable event stream */
+        arch_timer_evtstrm_enable(min(pos, 15));
+}
+
 static int arch_timer_setup(struct clock_event_device *clk)
 {
         __arch_timer_setup(ARCH_CP15_TIMER, clk);
@@ -307,6 +321,8 @@ static int arch_timer_setup(struct clock_event_device *clk)
         }
 
         arch_counter_set_user_access();
+        if (IS_ENABLED(CONFIG_ARM_ARCH_TIMER_EVTSTREAM))
+                arch_timer_configure_evtstream();
 
         return 0;
 }
@@ -460,6 +476,33 @@ static struct notifier_block arch_timer_cpu_nb = {
         .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;
@@ -499,11 +542,17 @@ 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);