3 files changed, 32 insertions, 0 deletions

diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
index 41c69469ce20..559d80335446 100644
--- a/drivers/clocksource/Kconfig
+++ b/drivers/clocksource/Kconfig
@@ -74,6 +74,21 @@ 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 fbd9ccd5e114..105f8ffa66a8 100644
--- a/drivers/clocksource/arm_arch_timer.c
+++ b/drivers/clocksource/arm_arch_timer.c
@@ -294,6 +294,19 @@ 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 +320,8 @@ 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;
 }
diff --git a/include/clocksource/arm_arch_timer.h b/include/clocksource/arm_arch_timer.h
index 8707dae4cee2..6d26b40cbf5d 100644
--- a/include/clocksource/arm_arch_timer.h
+++ b/include/clocksource/arm_arch_timer.h
@@ -41,6 +41,8 @@ enum arch_timer_reg {
 #define ARCH_TIMER_USR_VT_ACCESS_EN     (1 << 8) /* virtual timer registers */
 #define ARCH_TIMER_USR_PT_ACCESS_EN     (1 << 9) /* physical timer registers */
 
+#define ARCH_TIMER_EVT_STREAM_FREQ      10000   /* 100us */
+
 #ifdef CONFIG_ARM_ARCH_TIMER
 
 extern u32 arch_timer_get_rate(void);