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authorWill Deacon <will.deacon@arm.com>2013-08-23 18:32:29 +0400
committerSudeep KarkadaNagesha <sudeep.karkadanagesha@arm.com>2013-09-26 12:48:00 +0400
commit037f637767a82907efedda78d3ff405c34020075 (patch)
tree4478cc520fe744be36b559182bd36cbf8f61e705 /drivers/clocksource/arm_arch_timer.c
parent46efe547aca8498d51b64460c02366ae4032ca32 (diff)
downloadlinux-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.c15
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;
}