On 29/08/13 16:39, Catalin Marinas wrote: > On Thu, Aug 29, 2013 at 03:55:41PM +0100, Sudeep KarkadaNagesha wrote: >> From: Will Deacon <will.dea...@arm.com> >> >> 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 impose a time-out on a wfe polling loop. >> - To safeguard against any programming error in case an expected event >> is not generated. >> - To implement wfe-based timeouts for userspace locking implementations. >> >> 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.pieral...@arm.com> >> Cc: Catalin Marinas <catalin.mari...@arm.com> >> Signed-off-by: Will Deacon <will.dea...@arm.com> >> [sudeep: moving ARM/ARM64 changes into separate patches >> and adding Kconfig option] >> Signed-off-by: Sudeep KarkadaNagesha <sudeep.karkadanage...@arm.com> >> --- >> drivers/clocksource/Kconfig | 14 ++++++++++++++ >> drivers/clocksource/arm_arch_timer.c | 15 +++++++++++++++ >> include/clocksource/arm_arch_timer.h | 2 ++ >> 3 files changed, 31 insertions(+) >> >> diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig >> index b7b9b04..49f1f6e 100644 >> --- a/drivers/clocksource/Kconfig >> +++ b/drivers/clocksource/Kconfig >> @@ -74,6 +74,20 @@ 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. An event stream might be mainly useful >> + for wfe-based timeouts for userspace locking implementations. > > I would be a bit more assertive here, something like "the main use of > the event stream is wfe-based timeouts of userspace locking > implementations." > >> + It might also be useful for imposing timeout on a wfe or even >> + safeguarding against any programming errors in case an expected > > Maybe "imposting timeout on wfe to safeguard against ...". We already > mentioned wfe-based timeout above. > Ok will fix this Kconfig description.
> Otherwise, for the whole series: > > Reviewed-by: Catalin Marinas <catalin.mari...@arm.com> > Thanks. Regards, Sudeep -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
