IOMMU Archive on lore.kernel.org
 help / color / Atom feed
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
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

_______________________________________________
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu

  parent reply index

Thread overview: 54+ 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
2019-06-18 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

Reply instructions:

You may reply publically to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=1558660583-28561-4-git-send-email-ricardo.neri-calderon@linux.intel.com \
    --to=ricardo.neri-calderon@linux.intel.com \
    --cc=andi.kleen@intel.com \
    --cc=arnd@arndb.de \
    --cc=ashok.raj@intel.com \
    --cc=bp@suse.de \
    --cc=clemens@ladisch.de \
    --cc=eranian@google.com \
    --cc=hpa@zytor.com \
    --cc=iommu@lists.linux-foundation.org \
    --cc=kstewart@linuxfoundation.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mingo@kernel.org \
    --cc=peterz@infradead.org \
    --cc=pombredanne@nexb.com \
    --cc=rafael.j.wysocki@intel.com \
    --cc=ravi.v.shankar@intel.com \
    --cc=rdunlap@infradead.org \
    --cc=ricardo.neri@intel.com \
    --cc=tglx@linutronix.de \
    --cc=tony.luck@intel.com \
    --cc=x86@kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

IOMMU Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-iommu/0 linux-iommu/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-iommu linux-iommu/ https://lore.kernel.org/linux-iommu \
		iommu@lists.linux-foundation.org iommu@archiver.kernel.org
	public-inbox-index linux-iommu


Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.linux-foundation.lists.iommu


AGPL code for this site: git clone https://public-inbox.org/ public-inbox