From: Thomas Gleixner <tglx@linutronix.de>
To: LKML <linux-kernel@vger.kernel.org>
Cc: x86@kernel.org, Peter Zijlstra <peterz@infradead.org>,
Ricardo Neri <ricardo.neri-calderon@linux.intel.com>,
Ashok Raj <ashok.raj@intel.com>,
Andi Kleen <andi.kleen@intel.com>,
Suravee Suthikulpanit <Suravee.Suthikulpanit@amd.com>,
Stephane Eranian <eranian@google.com>,
Ravi Shankar <ravi.v.shankar@intel.com>,
Ingo Molnar <mingo@kernel.org>
Subject: [patch 16/29] x86/hpet: Clean up comments
Date: Sun, 23 Jun 2019 15:23:56 +0200 [thread overview]
Message-ID: <20190623132435.545653922@linutronix.de> (raw)
In-Reply-To: 20190623132340.463097504@linutronix.de
From: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
arch/x86/kernel/hpet.c | 41 +++++++++++++++++++++++------------------
1 file changed, 23 insertions(+), 18 deletions(-)
--- a/arch/x86/kernel/hpet.c
+++ b/arch/x86/kernel/hpet.c
@@ -266,8 +266,8 @@ static void hpet_legacy_clockevent_regis
hpet_enable_legacy_int();
/*
- * Start HPET with the boot cpu mask and make it
- * global after the IO_APIC has been initialized.
+ * Start HPET with the boot CPU's cpumask and make it global after
+ * the IO_APIC has been initialized.
*/
hpet_clockevent.cpumask = cpumask_of(boot_cpu_data.cpu_index);
clockevents_config_and_register(&hpet_clockevent, hpet_freq,
@@ -688,10 +688,10 @@ static inline void hpet_reserve_msi_time
/*
* Reading the HPET counter is a very slow operation. If a large number of
* CPUs are trying to access the HPET counter simultaneously, it can cause
- * massive delay and slow down system performance dramatically. This may
+ * massive delays and slow down system performance dramatically. This may
* happen when HPET is the default clock source instead of TSC. For a
* really large system with hundreds of CPUs, the slowdown may be so
- * severe that it may actually crash the system because of a NMI watchdog
+ * severe, that it can actually crash the system because of a NMI watchdog
* soft lockup, for example.
*
* If multiple CPUs are trying to access the HPET counter at the same time,
@@ -700,8 +700,7 @@ static inline void hpet_reserve_msi_time
*
* This special feature is only enabled on x86-64 systems. It is unlikely
* that 32-bit x86 systems will have enough CPUs to require this feature
- * with its associated locking overhead. And we also need 64-bit atomic
- * read.
+ * with its associated locking overhead. We also need 64-bit atomic read.
*
* The lock and the HPET value are stored together and can be read in a
* single atomic 64-bit read. It is explicitly assumed that arch_spinlock_t
@@ -1020,19 +1019,25 @@ void hpet_disable(void)
#ifdef CONFIG_HPET_EMULATE_RTC
-/* HPET in LegacyReplacement Mode eats up RTC interrupt line. When, HPET
+/*
+ * HPET in LegacyReplacement mode eats up the RTC interrupt line. When HPET
* is enabled, we support RTC interrupt functionality in software.
+ *
* RTC has 3 kinds of interrupts:
- * 1) Update Interrupt - generate an interrupt, every sec, when RTC clock
- * is updated
- * 2) Alarm Interrupt - generate an interrupt at a specific time of day
- * 3) Periodic Interrupt - generate periodic interrupt, with frequencies
- * 2Hz-8192Hz (2Hz-64Hz for non-root user) (all freqs in powers of 2)
- * (1) and (2) above are implemented using polling at a frequency of
- * 64 Hz. The exact frequency is a tradeoff between accuracy and interrupt
- * overhead. (DEFAULT_RTC_INT_FREQ)
- * For (3), we use interrupts at 64Hz or user specified periodic
- * frequency, whichever is higher.
+ *
+ * 1) Update Interrupt - generate an interrupt, every second, when the
+ * RTC clock is updated
+ * 2) Alarm Interrupt - generate an interrupt at a specific time of day
+ * 3) Periodic Interrupt - generate periodic interrupt, with frequencies
+ * 2Hz-8192Hz (2Hz-64Hz for non-root user) (all frequencies in powers of 2)
+ *
+ * (1) and (2) above are implemented using polling at a frequency of 64 Hz:
+ * DEFAULT_RTC_INT_FREQ.
+ *
+ * The exact frequency is a tradeoff between accuracy and interrupt overhead.
+ *
+ * For (3), we use interrupts at 64 Hz, or the user specified periodic frequency,
+ * if it's higher.
*/
#include <linux/mc146818rtc.h>
#include <linux/rtc.h>
@@ -1053,7 +1058,7 @@ static unsigned long hpet_pie_limit;
static rtc_irq_handler irq_handler;
/*
- * Check that the HPET counter c1 is ahead of the c2
+ * Check that the HPET counter c1 is ahead of c2
*/
static inline int hpet_cnt_ahead(u32 c1, u32 c2)
{
next prev parent reply other threads:[~2019-06-23 13:27 UTC|newest]
Thread overview: 66+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-23 13:23 [patch 00/29] x86/hpet: Cleanup the channel management Thomas Gleixner
2019-06-23 13:23 ` [patch 01/29] x86/hpet: Simplify CPU online code Thomas Gleixner
2019-06-27 23:34 ` [tip:x86/timers] " tip-bot for Thomas Gleixner
2019-06-23 13:23 ` [patch 02/29] x86/hpet: Replace printk(KERN...) with pr_...() Thomas Gleixner
2019-06-27 23:34 ` [tip:x86/timers] " tip-bot for Thomas Gleixner
2019-06-23 13:23 ` [patch 03/29] x86/hpet: Restructure init code Thomas Gleixner
2019-06-27 23:35 ` [tip:x86/timers] " tip-bot for Thomas Gleixner
2019-06-23 13:23 ` [patch 04/29] x86/hpet: Remove pointless x86-64 specific #include Thomas Gleixner
2019-06-27 23:36 ` [tip:x86/timers] " tip-bot for Thomas Gleixner
2019-06-23 13:23 ` [patch 05/29] x86/hpet: Remove unused parameter from hpet_next_event() Thomas Gleixner
2019-06-27 23:36 ` [tip:x86/timers] " tip-bot for Thomas Gleixner
2019-06-23 13:23 ` [patch 06/29] x86/hpet: Remove the unused hpet_msi_read() function Thomas Gleixner
2019-06-27 23:37 ` [tip:x86/timers] " tip-bot for Thomas Gleixner
2019-06-23 13:23 ` [patch 07/29] x86/hpet: Mark init functions __init Thomas Gleixner
2019-06-27 23:38 ` [tip:x86/timers] " tip-bot for Thomas Gleixner
2019-06-23 13:23 ` [patch 08/29] x86/hpet: Sanitize stub functions Thomas Gleixner
2019-06-27 23:39 ` [tip:x86/timers] " tip-bot for Thomas Gleixner
2019-06-23 13:23 ` [patch 09/29] x86/hpet: Move static and global variables to one place Thomas Gleixner
2019-06-27 23:39 ` [tip:x86/timers] " tip-bot for Thomas Gleixner
2019-06-23 13:23 ` [patch 10/29] x86/hpet: Shuffle code around for readability sake Thomas Gleixner
2019-06-27 23:40 ` [tip:x86/timers] " tip-bot for Thomas Gleixner
2019-06-23 13:23 ` [patch 11/29] x86/hpet: Separate counter check out of clocksource register code Thomas Gleixner
2019-06-27 23:41 ` [tip:x86/timers] " tip-bot for Thomas Gleixner
2019-06-23 13:23 ` [patch 12/29] x86/hpet: Simplify counter validation Thomas Gleixner
2019-06-27 23:41 ` [tip:x86/timers] " tip-bot for Thomas Gleixner
2019-06-23 13:23 ` [patch 13/29] x86/hpet: Decapitalize and rename EVT_TO_HPET_DEV Thomas Gleixner
2019-06-27 23:42 ` [tip:x86/timers] " tip-bot for Thomas Gleixner
2019-06-23 13:23 ` [patch 14/29] x86/hpet: Remove not required includes Thomas Gleixner
2019-06-27 23:43 ` [tip:x86/timers] " tip-bot for Ingo Molnar
2019-06-23 13:23 ` [patch 15/29] x86/hpet: Make naming consistent Thomas Gleixner
2019-06-27 23:44 ` [tip:x86/timers] " tip-bot for Ingo Molnar
2019-06-23 13:23 ` Thomas Gleixner [this message]
2019-06-27 23:44 ` [tip:x86/timers] x86/hpet: Clean up comments tip-bot for Ingo Molnar
2019-06-23 13:23 ` [patch 17/29] x86/hpet: Coding style cleanup Thomas Gleixner
2019-06-27 23:45 ` [tip:x86/timers] " tip-bot for Ingo Molnar
2019-06-23 13:23 ` [patch 18/29] x86/hpet: Introduce struct hpet_base and struct hpet_channel Thomas Gleixner
2019-06-27 23:46 ` [tip:x86/timers] " tip-bot for Thomas Gleixner
2019-06-23 13:23 ` [patch 19/29] x86/hpet: Use cached channel data Thomas Gleixner
2019-06-27 23:46 ` [tip:x86/timers] " tip-bot for Thomas Gleixner
2019-06-23 13:24 ` [patch 20/29] x86/hpet: Add mode information to struct hpet_channel Thomas Gleixner
2019-06-27 23:47 ` [tip:x86/timers] " tip-bot for Thomas Gleixner
2019-06-23 13:24 ` [patch 21/29] x86/hpet: Add function to select a /dev/hpet channel Thomas Gleixner
2019-06-27 23:48 ` [tip:x86/timers] " tip-bot for Thomas Gleixner
2019-06-23 13:24 ` [patch 22/29] x86/hpet: Rename variables to prepare for switching to channels Thomas Gleixner
2019-06-27 23:49 ` [tip:x86/timers] " tip-bot for Ingo Molnar
2019-06-23 13:24 ` [patch 23/29] x86/hpet: Move clockevents into channels Thomas Gleixner
2019-06-27 23:49 ` [tip:x86/timers] " tip-bot for Thomas Gleixner
2019-06-23 13:24 ` [patch 24/29] x86/hpet: Use cached info instead of extra flags Thomas Gleixner
2019-06-26 21:20 ` Ingo Molnar
2019-06-27 23:50 ` [tip:x86/timers] " tip-bot for Thomas Gleixner
2019-06-23 13:24 ` [patch 25/29] x86/hpet: Wrap legacy clockevent in hpet_channel Thomas Gleixner
2019-06-27 23:51 ` [tip:x86/timers] " tip-bot for Thomas Gleixner
2019-06-23 13:24 ` [patch 26/29] x86/hpet: Consolidate clockevent functions Thomas Gleixner
2019-06-26 21:17 ` Ingo Molnar
2019-06-27 22:44 ` Thomas Gleixner
2019-06-27 22:53 ` Thomas Gleixner
2019-06-28 8:32 ` Ingo Molnar
2019-06-27 23:51 ` [tip:x86/timers] " tip-bot for Thomas Gleixner
2019-06-23 13:24 ` [patch 27/29] x86/hpet: Carve out shareable parts of init_one_hpet_msi_clockevent() Thomas Gleixner
2019-06-27 23:52 ` [tip:x86/timers] " tip-bot for Thomas Gleixner
2019-06-23 13:24 ` [patch 28/29] x86/hpet: Use common init for legacy clockevent Thomas Gleixner
2019-06-26 21:13 ` Ingo Molnar
2019-06-27 23:53 ` [tip:x86/timers] " tip-bot for Thomas Gleixner
2019-06-23 13:24 ` [patch 29/29] x86/hpet: Use channel for legacy clockevent storage Thomas Gleixner
2019-06-27 23:53 ` [tip:x86/timers] " tip-bot for Thomas Gleixner
2019-06-26 21:22 ` [patch 00/29] x86/hpet: Cleanup the channel management Ingo Molnar
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