From: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
To: Randy Dunlap <rdunlap@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@kernel.org>, Borislav Petkov <bp@suse.de>,
Ashok Raj <ashok.raj@intel.com>, Joerg Roedel <joro@8bytes.org>,
Andi Kleen <andi.kleen@intel.com>,
Peter Zijlstra <peterz@infradead.org>,
"Ravi V. Shankar" <ravi.v.shankar@intel.com>,
x86@kernel.org, linux-kernel@vger.kernel.org,
iommu@lists.linux-foundation.org,
Ricardo Neri <ricardo.neri@intel.com>,
"H. Peter Anvin" <hpa@zytor.com>, Tony Luck <tony.luck@intel.com>,
Clemens Ladisch <clemens@ladisch.de>,
Arnd Bergmann <arnd@arndb.de>,
Philippe Ombredanne <pombredanne@nexb.com>,
Kate Stewart <kstewart@linuxfoundation.org>,
"Rafael J. Wysocki" <rafael.j.wysocki@intel.com>,
Stephane Eranian <eranian@google.com>,
Suravee Suthikulpanit <Suravee.Suthikulpanit@amd.com>
Subject: Re: [RFC PATCH v3 03/21] x86/hpet: Calculate ticks-per-second in a separate function
Date: Wed, 15 May 2019 08:54:26 -0700 [thread overview]
Message-ID: <20190515155426.GA10526@ranerica-svr.sc.intel.com> (raw)
In-Reply-To: <25922025-d551-0865-b364-b53ef34e6b6a@infradead.org>
On Tue, May 14, 2019 at 07:23:47AM -0700, Randy Dunlap wrote:
> On 5/14/19 7:01 AM, Ricardo Neri wrote:
> > It is easier to compute the expiration times of an HPET timer by using
> > its frequency (i.e., the number of times it ticks in a second) than its
> > period, as given in the capabilities register.
> >
> > In addition to the HPET char driver, the HPET-based hardlockup detector
> > will also need to know the timer's frequency. Thus, create a common
> > function that both can use.
> >
> > Cc: "H. Peter Anvin" <hpa@zytor.com>
> > Cc: Ashok Raj <ashok.raj@intel.com>
> > Cc: Andi Kleen <andi.kleen@intel.com>
> > Cc: Tony Luck <tony.luck@intel.com>
> > Cc: Clemens Ladisch <clemens@ladisch.de>
> > Cc: Arnd Bergmann <arnd@arndb.de>
> > Cc: Philippe Ombredanne <pombredanne@nexb.com>
> > Cc: Kate Stewart <kstewart@linuxfoundation.org>
> > Cc: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
> > Cc: Stephane Eranian <eranian@google.com>
> > Cc: Suravee Suthikulpanit <Suravee.Suthikulpanit@amd.com>
> > Cc: "Ravi V. Shankar" <ravi.v.shankar@intel.com>
> > Cc: x86@kernel.org
> > Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
> > ---
> > drivers/char/hpet.c | 31 ++++++++++++++++++++++++-------
> > include/linux/hpet.h | 1 +
> > 2 files changed, 25 insertions(+), 7 deletions(-)
> >
> > diff --git a/drivers/char/hpet.c b/drivers/char/hpet.c
> > index d0ad85900b79..bdcbecfdb858 100644
> > --- a/drivers/char/hpet.c
> > +++ b/drivers/char/hpet.c
> > @@ -836,6 +836,29 @@ static unsigned long hpet_calibrate(struct hpets *hpetp)
> > return ret;
> > }
> >
> > +u64 hpet_get_ticks_per_sec(u64 hpet_caps)
> > +{
> > + u64 ticks_per_sec, period;
> > +
> > + period = (hpet_caps & HPET_COUNTER_CLK_PERIOD_MASK) >>
> > + HPET_COUNTER_CLK_PERIOD_SHIFT; /* fs, 10^-15 */
> > +
> > + /*
> > + * The frequency is the reciprocal of the period. The period is given
> > + * femtoseconds per second. Thus, prepare a dividend to obtain the
>
> * in femtoseconds per second.
>
Thanks for your review Randy! I'll fix this grammar issue.
> > + * frequency in ticks per second.
> > + */
> > +
> > + /* 10^15 femtoseconds per second */
> > + ticks_per_sec = 1000000000000000uLL;
>
> ULL is overwhelmingly used in the kernel.
>
Sure, I'll update it.
BR,
Ricardo
next prev parent reply other threads:[~2019-05-15 15:56 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-14 14:01 [RFC PATCH v3 00/21] Implement an HPET-based hardlockup detector Ricardo Neri
2019-05-14 14:01 ` [RFC PATCH v3 01/21] x86/msi: Add definition for NMI delivery mode Ricardo Neri
2019-05-14 14:01 ` [RFC PATCH v3 02/21] x86/hpet: Expose hpet_writel() in header Ricardo Neri
2019-05-14 14:01 ` [RFC PATCH v3 03/21] x86/hpet: Calculate ticks-per-second in a separate function Ricardo Neri
2019-05-14 14:23 ` Randy Dunlap
2019-05-15 15:54 ` Ricardo Neri [this message]
2019-05-14 14:01 ` [RFC PATCH v3 04/21] x86/hpet: Add hpet_set_comparator() for periodic and one-shot modes Ricardo Neri
2019-05-14 14:24 ` Randy Dunlap
2019-05-15 15:56 ` Ricardo Neri
2019-05-14 14:01 ` [RFC PATCH v3 05/21] x86/hpet: Reserve timer for the HPET hardlockup detector Ricardo Neri
2019-05-14 14:01 ` [RFC PATCH v3 06/21] x86/hpet: Configure the timer used by the " Ricardo Neri
2019-05-14 14:02 ` [RFC PATCH v3 07/21] watchdog/hardlockup: Define a generic function to detect hardlockups Ricardo Neri
2019-05-14 14:02 ` [RFC PATCH v3 08/21] watchdog/hardlockup: Decouple the hardlockup detector from perf Ricardo Neri
2019-05-14 14:02 ` [RFC PATCH v3 09/21] x86/nmi: Add a NMI_WATCHDOG NMI handler category Ricardo Neri
2019-05-14 14:02 ` [RFC PATCH v3 10/21] watchdog/hardlockup: Add function to enable NMI watchdog on all allowed CPUs at once Ricardo Neri
2019-05-14 14:02 ` [RFC PATCH v3 11/21] x86/watchdog/hardlockup: Add an HPET-based hardlockup detector Ricardo Neri
2019-05-14 14:26 ` Randy Dunlap
2019-05-15 15:56 ` Ricardo Neri
2019-05-14 14:02 ` [RFC PATCH v3 12/21] watchdog/hardlockup/hpet: Adjust timer expiration on the number of monitored CPUs Ricardo Neri
2019-05-14 14:02 ` [RFC PATCH v3 13/21] x86/watchdog/hardlockup/hpet: Determine if HPET timer caused NMI Ricardo Neri
2019-05-14 14:02 ` [RFC PATCH v3 14/21] watchdog/hardlockup: Use parse_option_str() to handle "nmi_watchdog" Ricardo Neri
2019-05-14 14:02 ` [RFC PATCH v3 15/21] watchdog/hardlockup/hpet: Only enable the HPET watchdog via a boot parameter Ricardo Neri
2019-05-14 14:02 ` [RFC PATCH v3 16/21] x86/watchdog: Add a shim hardlockup detector Ricardo Neri
2019-05-14 14:02 ` [RFC PATCH v3 17/21] x86/tsc: Switch to perf-based hardlockup detector if TSC become unstable Ricardo Neri
2019-05-14 14:02 ` [RFC PATCH v3 18/21] x86/apic: Add a parameter for the APIC delivery mode Ricardo Neri
2019-05-14 14:02 ` [RFC PATCH v3 19/21] iommu/vt-d: Rework prepare_irte() to support per-irq " Ricardo Neri
2019-05-14 14:02 ` [RFC PATCH v3 20/21] iommu/vt-d: hpet: Reserve an interrupt remampping table entry for watchdog Ricardo Neri
2019-05-14 14:02 ` [RFC PATCH v3 21/21] x86/watchdog/hardlockup/hpet: Support interrupt remapping Ricardo Neri
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