diff options
author | Will Deacon <will.deacon@arm.com> | 2013-08-23 18:32:29 +0400 |
---|---|---|
committer | Sudeep KarkadaNagesha <sudeep.karkadanagesha@arm.com> | 2013-09-26 12:48:00 +0400 |
commit | 037f637767a82907efedda78d3ff405c34020075 (patch) | |
tree | 4478cc520fe744be36b559182bd36cbf8f61e705 /drivers/clocksource/arm_arch_timer.c | |
parent | 46efe547aca8498d51b64460c02366ae4032ca32 (diff) | |
download | linux-037f637767a82907efedda78d3ff405c34020075.tar.xz |
drivers: clocksource: add support for ARM architected timer event stream
The ARM architected timer can generate events (used for waking up
CPUs executing the wfe instruction) at a frequency represented as a
power-of-2 divisor of the clock rate.
An event stream might be used:
- To implement wfe-based timeouts for userspace locking implementations.
- To impose a timeout on a wfe for safeguarding against any programming
error in case an expected event is not generated.
This patch computes the event stream frequency aiming for a period
of 100us between events. It uses ARM/ARM64 specific backends to configure
and enable the event stream.
Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Olof Johansson <olof@lixom.net>
Signed-off-by: Will Deacon <will.deacon@arm.com>
[sudeep: moving ARM/ARM64 changes into separate patches
and adding Kconfig option]
Signed-off-by: Sudeep KarkadaNagesha <sudeep.karkadanagesha@arm.com>
Diffstat (limited to 'drivers/clocksource/arm_arch_timer.c')
-rw-r--r-- | drivers/clocksource/arm_arch_timer.c | 15 |
1 files changed, 15 insertions, 0 deletions
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; } |