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authorWill Deacon <will.deacon@arm.com>2016-06-27 17:30:13 +0100
committerDaniel Lezcano <daniel.lezcano@linaro.org>2016-06-28 11:35:50 +0200
commit46fd5c6b3059462131caa4d52691c9c5666c3223 (patch)
tree244b0ef16720d6d715d3b312ef009085ea8b09b3 /drivers/clocksource
parent5cc87a4df5009c1cbe9e087ad16c0bacdae06809 (diff)
downloadlinux-46fd5c6b3059462131caa4d52691c9c5666c3223.tar.bz2
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>
Diffstat (limited to 'drivers/clocksource')
-rw-r--r--drivers/clocksource/Kconfig12
-rw-r--r--drivers/clocksource/arm_arch_timer.c10
2 files changed, 16 insertions, 6 deletions
diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
index 7acdf3d735ac..567788664723 100644
--- a/drivers/clocksource/Kconfig
+++ b/drivers/clocksource/Kconfig
@@ -288,14 +288,16 @@ config ARM_ARCH_TIMER
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
diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c
index 9e33309ad2ea..5effd3027319 100644
--- a/drivers/clocksource/arm_arch_timer.c
+++ b/drivers/clocksource/arm_arch_timer.c
@@ -79,6 +79,14 @@ static enum ppi_nr arch_timer_uses_ppi = VIRT_PPI;
static bool arch_timer_c3stop;
static bool arch_timer_mem_use_virtual;
+static bool evtstrm_enable = IS_ENABLED(CONFIG_ARM_ARCH_TIMER_EVTSTREAM);
+
+static int __init early_evtstrm_cfg(char *buf)
+{
+ return strtobool(buf, &evtstrm_enable);
+}
+early_param("clocksource.arm_arch_timer.evtstrm", early_evtstrm_cfg);
+
/*
* Architected system timer support.
*/
@@ -372,7 +380,7 @@ static int arch_timer_setup(struct clock_event_device *clk)
enable_percpu_irq(arch_timer_ppi[PHYS_NONSECURE_PPI], 0);
arch_counter_set_user_access();
- if (IS_ENABLED(CONFIG_ARM_ARCH_TIMER_EVTSTREAM))
+ if (evtstrm_enable)
arch_timer_configure_evtstream();
return 0;