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authorWill Deacon <will.deacon@arm.com>2013-08-23 15:32:29 +0100
committerAlex Shi <alex.shi@linaro.org>2014-04-14 21:17:15 +0800
commitc2fd237d23007adf60014e778f17bb6c9991942c (patch)
tree540e024062e0d9b5439e919a47a42a0245ec1460
parentffc38694880cedb29b92af42a8c0d80ce0e5afbe (diff)
downloadlinux-linaro-stable-c2fd237d23007adf60014e778f17bb6c9991942c.tar.gz
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> (cherry picked from commit 037f637767a82907efedda78d3ff405c34020075) Signed-off-by: Alex Shi <alex.shi@linaro.org> Conflicts: drivers/clocksource/Kconfig drivers/clocksource/arm_arch_timer.c
-rw-r--r--drivers/clocksource/Kconfig15
-rw-r--r--drivers/clocksource/arm_arch_timer.c15
-rw-r--r--include/clocksource/arm_arch_timer.h2
3 files changed, 32 insertions, 0 deletions
diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
index f151c6cf27c3..593485b02ee5 100644
--- a/drivers/clocksource/Kconfig
+++ b/drivers/clocksource/Kconfig
@@ -67,6 +67,21 @@ 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 CLKSRC_METAG_GENERIC
def_bool y if METAG
help
diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c
index 053d846ab5b1..d8f7eecce100 100644
--- a/drivers/clocksource/arm_arch_timer.c
+++ b/drivers/clocksource/arm_arch_timer.c
@@ -123,6 +123,19 @@ static int arch_timer_set_next_event_phys(unsigned long evt,
return 0;
}
+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 __cpuinit arch_timer_setup(struct clock_event_device *clk)
{
clk->features = CLOCK_EVT_FEAT_ONESHOT | CLOCK_EVT_FEAT_C3STOP;
@@ -154,6 +167,8 @@ static int __cpuinit 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 551f7e918120..c4d0fc4855ab 100644
--- a/include/clocksource/arm_arch_timer.h
+++ b/include/clocksource/arm_arch_timer.h
@@ -37,6 +37,8 @@
#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);