clocksource/drivers/arm_arch_timer: Control the evtstrm via the cmdline
Disabling the eventstream can be useful for both remotely debugging a
deployed production system and development of code using WFE-based
polling loops. Whilst this can currently be controlled via a Kconfig
option (CONFIG_ARM_ARCH_TIMER_EVTSTREAM), it's often desirable to toggle
the feature on the command line, so this patch adds a new command-line
option ("clocksource.arm_arch_timer.evtstrm") to do just that. The
default behaviour is determined based on CONFIG_ARM_ARCH_TIMER_EVTSTREAM.
Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
index 7acdf3d..5677886 100644
--- a/drivers/clocksource/Kconfig
+++ b/drivers/clocksource/Kconfig
@@ -288,14 +288,16 @@
select CLKSRC_ACPI if ACPI
config ARM_ARCH_TIMER_EVTSTREAM
- bool "Support for ARM architected timer event stream generation"
+ bool "Enable ARM architected timer event stream generation by default"
default y if ARM_ARCH_TIMER
depends on 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.
+ This option enables support by default 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 behaviour can also be
+ overridden on the command line using the
+ clocksource.arm_arch_timer.evtstream parameter.
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