From 037f637767a82907efedda78d3ff405c34020075 Mon Sep 17 00:00:00 2001 From: Will Deacon Date: Fri, 23 Aug 2013 15:32:29 +0100 Subject: 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 Reviewed-by: Catalin Marinas Acked-by: Olof Johansson Signed-off-by: Will Deacon [sudeep: moving ARM/ARM64 changes into separate patches and adding Kconfig option] Signed-off-by: Sudeep KarkadaNagesha --- drivers/clocksource/Kconfig | 15 +++++++++++++++ 1 file changed, 15 insertions(+) (limited to 'drivers/clocksource/Kconfig') diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig index 41c6946..559d803 100644 --- a/drivers/clocksource/Kconfig +++ b/drivers/clocksource/Kconfig @@ -74,6 +74,21 @@ 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 ARM_GLOBAL_TIMER bool select CLKSRC_OF if OF -- cgit v1.1