From: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
To: Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@kernel.org>, Borislav Petkov <bp@suse.de>
Cc: Kate Stewart <kstewart@linuxfoundation.org>,
"Ravi V. Shankar" <ravi.v.shankar@intel.com>,
x86@kernel.org, Ashok Raj <ashok.raj@intel.com>,
Arnd Bergmann <arnd@arndb.de>,
Peter Zijlstra <peterz@infradead.org>,
Ricardo Neri <ricardo.neri-calderon@linux.intel.com>,
Randy Dunlap <rdunlap@infradead.org>,
Clemens Ladisch <clemens@ladisch.de>,
linux-kernel@vger.kernel.org,
Stephane Eranian <eranian@google.com>,
Ricardo Neri <ricardo.neri@intel.com>,
"Rafael J. Wysocki" <rafael.j.wysocki@intel.com>,
iommu@lists.linux-foundation.org, Tony Luck <tony.luck@intel.com>,
"H. Peter Anvin" <hpa@zytor.com>,
Andi Kleen <andi.kleen@intel.com>,
Philippe Ombredanne <pombredanne@nexb.com>
Subject: [RFC PATCH v4 03/21] x86/hpet: Calculate ticks-per-second in a separate function
Date: Thu, 23 May 2019 18:16:05 -0700 [thread overview]
Message-ID: <1558660583-28561-4-git-send-email-ricardo.neri-calderon@linux.intel.com> (raw)
In-Reply-To: <1558660583-28561-1-git-send-email-ricardo.neri-calderon@linux.intel.com>
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 3a1e6b3ccd10..747255f552a9 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
+ * in femtoseconds per second. Thus, prepare a dividend to obtain the
+ * frequency in ticks per second.
+ */
+
+ /* 10^15 femtoseconds per second */
+ ticks_per_sec = 1000000000000000ULL;
+ ticks_per_sec += period >> 1; /* round */
+
+ /* The quotient is put in the dividend. We drop the remainder. */
+ do_div(ticks_per_sec, period);
+
+ return ticks_per_sec;
+}
+
int hpet_alloc(struct hpet_data *hdp)
{
u64 cap, mcfg;
@@ -844,7 +867,6 @@ int hpet_alloc(struct hpet_data *hdp)
struct hpets *hpetp;
struct hpet __iomem *hpet;
static struct hpets *last;
- unsigned long period;
unsigned long long temp;
u32 remainder;
@@ -894,12 +916,7 @@ int hpet_alloc(struct hpet_data *hdp)
last = hpetp;
- period = (cap & HPET_COUNTER_CLK_PERIOD_MASK) >>
- HPET_COUNTER_CLK_PERIOD_SHIFT; /* fs, 10^-15 */
- temp = 1000000000000000uLL; /* 10^15 femtoseconds per second */
- temp += period >> 1; /* round */
- do_div(temp, period);
- hpetp->hp_tick_freq = temp; /* ticks per second */
+ hpetp->hp_tick_freq = hpet_get_ticks_per_sec(cap);
printk(KERN_INFO "hpet%d: at MMIO 0x%lx, IRQ%s",
hpetp->hp_which, hdp->hd_phys_address,
diff --git a/include/linux/hpet.h b/include/linux/hpet.h
index 8604564b985d..e7b36bcf4699 100644
--- a/include/linux/hpet.h
+++ b/include/linux/hpet.h
@@ -107,5 +107,6 @@ static inline void hpet_reserve_timer(struct hpet_data *hd, int timer)
}
int hpet_alloc(struct hpet_data *);
+u64 hpet_get_ticks_per_sec(u64 hpet_caps);
#endif /* !__HPET__ */
--
2.17.1
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next prev parent reply other threads:[~2019-05-24 1:17 UTC|newest]
Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-24 1:16 [RFC PATCH v4 00/21] Implement an HPET-based hardlockup detector Ricardo Neri
2019-05-24 1:16 ` [RFC PATCH v4 01/21] x86/msi: Add definition for NMI delivery mode Ricardo Neri
2019-05-24 1:16 ` [RFC PATCH v4 02/21] x86/hpet: Expose hpet_writel() in header Ricardo Neri
2019-05-24 1:16 ` Ricardo Neri [this message]
2019-06-14 15:54 ` [RFC PATCH v4 03/21] x86/hpet: Calculate ticks-per-second in a separate function Thomas Gleixner
2019-06-14 15:59 ` Thomas Gleixner
2019-06-18 22:48 ` Ricardo Neri
2019-06-18 23:13 ` Thomas Gleixner
2019-05-24 1:16 ` [RFC PATCH v4 04/21] x86/hpet: Add hpet_set_comparator() for periodic and one-shot modes Ricardo Neri
2019-06-14 18:17 ` Thomas Gleixner
2019-06-18 22:48 ` Ricardo Neri
2019-05-24 1:16 ` [RFC PATCH v4 05/21] x86/hpet: Reserve timer for the HPET hardlockup detector Ricardo Neri
2019-06-11 19:54 ` Thomas Gleixner
2019-06-14 1:14 ` Ricardo Neri
2019-06-14 16:10 ` Thomas Gleixner
2019-06-18 22:48 ` Ricardo Neri
2019-05-24 1:16 ` [RFC PATCH v4 06/21] x86/hpet: Configure the timer used by the " Ricardo Neri
2019-05-24 1:16 ` [RFC PATCH v4 07/21] watchdog/hardlockup: Define a generic function to detect hardlockups Ricardo Neri
2019-05-24 1:16 ` [RFC PATCH v4 08/21] watchdog/hardlockup: Decouple the hardlockup detector from perf Ricardo Neri
2019-05-24 1:16 ` [RFC PATCH v4 09/21] x86/nmi: Add a NMI_WATCHDOG NMI handler category Ricardo Neri
2019-05-24 1:16 ` [RFC PATCH v4 10/21] watchdog/hardlockup: Add function to enable NMI watchdog on all allowed CPUs at once Ricardo Neri
2019-05-24 1:16 ` [RFC PATCH v4 11/21] x86/watchdog/hardlockup: Add an HPET-based hardlockup detector Ricardo Neri
2019-05-24 1:16 ` [RFC PATCH v4 12/21] watchdog/hardlockup/hpet: Adjust timer expiration on the number of monitored CPUs Ricardo Neri
2019-06-11 20:11 ` Thomas Gleixner
2019-06-18 22:46 ` Ricardo Neri
2019-05-24 1:16 ` [RFC PATCH v4 13/21] x86/watchdog/hardlockup/hpet: Determine if HPET timer caused NMI Ricardo Neri
2019-05-24 1:16 ` [RFC PATCH v4 14/21] watchdog/hardlockup: Use parse_option_str() to handle "nmi_watchdog" Ricardo Neri
2019-05-24 1:16 ` [RFC PATCH v4 15/21] watchdog/hardlockup/hpet: Only enable the HPET watchdog via a boot parameter Ricardo Neri
2019-05-24 1:16 ` [RFC PATCH v4 16/21] x86/watchdog: Add a shim hardlockup detector Ricardo Neri
2019-05-24 1:16 ` [RFC PATCH v4 17/21] x86/tsc: Switch to perf-based hardlockup detector if TSC become unstable Ricardo Neri
2019-06-07 0:35 ` Stephane Eranian via iommu
2019-06-07 14:14 ` Ricardo Neri
2019-05-24 1:16 ` [RFC PATCH v4 18/21] x86/apic: Add a parameter for the APIC delivery mode Ricardo Neri
2019-06-16 9:55 ` Thomas Gleixner
2019-06-18 22:47 ` Ricardo Neri
2019-06-18 23:15 ` Thomas Gleixner
2019-05-24 1:16 ` [RFC PATCH v4 19/21] iommu/vt-d: Rework prepare_irte() to support per-irq " Ricardo Neri
2019-05-24 1:16 ` [RFC PATCH v4 20/21] iommu/vt-d: hpet: Reserve an interrupt remampping table entry for watchdog Ricardo Neri
2019-06-16 18:42 ` Thomas Gleixner
2019-06-16 19:21 ` Thomas Gleixner
2019-06-17 8:25 ` Thomas Gleixner
2019-06-17 21:38 ` Stephane Eranian via iommu
2019-06-17 23:08 ` Thomas Gleixner
2019-06-19 15:43 ` Jacob Pan
2019-06-21 15:33 ` Thomas Gleixner
2019-06-21 17:31 ` Jacob Pan
2019-06-21 18:39 ` Jacob Pan
2019-06-21 20:05 ` Thomas Gleixner
2019-06-21 23:55 ` Ricardo Neri
2019-06-22 7:21 ` Thomas Gleixner
2019-10-18 2:48 ` Ricardo Neri
2019-06-18 22:45 ` Ricardo Neri
2019-05-24 1:16 ` [RFC PATCH v4 21/21] x86/watchdog/hardlockup/hpet: Support interrupt remapping Ricardo Neri
2019-06-16 8:44 ` Thomas Gleixner
2019-06-16 8:53 ` Thomas Gleixner
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