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. Otherwise, for the whole series: Reviewed-by: Catalin Marinas <catalin.mari...@arm.com> -- 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/
