From: Catalin Marinas <catalin.marinas@arm.com> To: Sudeep KarkadaNagesha <Sudeep.KarkadaNagesha@arm.com> Cc: "linux-arm-kernel@lists.infradead.org" <linux-arm-kernel@lists.infradead.org>, "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>, Lorenzo Pieralisi <Lorenzo.Pieralisi@arm.com>, Will Deacon <Will.Deacon@arm.com>, Thomas Gleixner <tglx@linutronix.de>, Daniel Lezcano <daniel.lezcano@linaro.org> Subject: Re: [PATCH v6 4/5] drivers: clocksource: add support for ARM architected timer event stream Date: Thu, 29 Aug 2013 16:39:14 +0100 [thread overview] Message-ID: <20130829153914.GA10707@darko.cambridge.arm.com> (raw) In-Reply-To: <1377788142-21388-5-git-send-email-Sudeep.KarkadaNagesha@arm.com> On Thu, Aug 29, 2013 at 03:55:41PM +0100, Sudeep KarkadaNagesha wrote: > From: Will Deacon <will.deacon@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.pieralisi@arm.com> > Cc: Catalin Marinas <catalin.marinas@arm.com> > 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> > --- > 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.marinas@arm.com>
WARNING: multiple messages have this Message-ID (diff)
From: catalin.marinas@arm.com (Catalin Marinas) To: linux-arm-kernel@lists.infradead.org Subject: [PATCH v6 4/5] drivers: clocksource: add support for ARM architected timer event stream Date: Thu, 29 Aug 2013 16:39:14 +0100 [thread overview] Message-ID: <20130829153914.GA10707@darko.cambridge.arm.com> (raw) In-Reply-To: <1377788142-21388-5-git-send-email-Sudeep.KarkadaNagesha@arm.com> On Thu, Aug 29, 2013 at 03:55:41PM +0100, Sudeep KarkadaNagesha wrote: > From: Will Deacon <will.deacon@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.pieralisi@arm.com> > Cc: Catalin Marinas <catalin.marinas@arm.com> > 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> > --- > 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.marinas@arm.com>
next prev parent reply other threads:[~2013-08-29 15:39 UTC|newest] Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top 2013-08-29 14:55 [PATCH v6 0/5] ARM/ARM64 architected timer updates Sudeep KarkadaNagesha 2013-08-29 14:55 ` Sudeep KarkadaNagesha 2013-08-29 14:55 ` [PATCH v6 1/5] ARM/ARM64: arch_timer: add macros for bits in control register Sudeep KarkadaNagesha 2013-08-29 14:55 ` Sudeep KarkadaNagesha 2013-08-29 14:55 ` [PATCH v6 2/5] ARM: arch_timer: add support to configure and enable event stream Sudeep KarkadaNagesha 2013-08-29 14:55 ` Sudeep KarkadaNagesha 2013-08-29 14:55 ` [PATCH v6 3/5] ARM64: " Sudeep KarkadaNagesha 2013-08-29 14:55 ` Sudeep KarkadaNagesha 2013-08-29 14:55 ` [PATCH v6 4/5] drivers: clocksource: add support for ARM architected timer " Sudeep KarkadaNagesha 2013-08-29 14:55 ` Sudeep KarkadaNagesha 2013-08-29 15:39 ` Catalin Marinas [this message] 2013-08-29 15:39 ` Catalin Marinas 2013-08-29 15:42 ` Sudeep KarkadaNagesha 2013-08-29 15:42 ` Sudeep KarkadaNagesha 2013-08-29 14:55 ` [PATCH v6 5/5] drivers: clocksource: add CPU PM notifier for ARM architected timer Sudeep KarkadaNagesha 2013-08-29 14:55 ` Sudeep KarkadaNagesha 2013-08-30 10:07 ` [PATCH v6 0/5] ARM/ARM64 architected timer updates Sudeep KarkadaNagesha 2013-08-30 10:07 ` Sudeep KarkadaNagesha 2013-08-30 11:43 ` Russell King - ARM Linux 2013-08-30 11:43 ` Russell King - ARM Linux 2013-08-30 14:04 ` Will Deacon 2013-08-30 14:04 ` Will Deacon 2013-08-30 15:46 ` Sudeep KarkadaNagesha 2013-08-30 15:46 ` Sudeep KarkadaNagesha 2013-08-30 16:35 ` Catalin Marinas 2013-08-30 16:35 ` Catalin Marinas
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