Messages in this thread Patch in this message |  | | | From | John Stultz <> | | Subject | [PATCH 2/2] x86/hpet: Use the FSEC_PER_SEC constant for femto-second periods | | Date | Mon, 9 Aug 2010 14:20:10 -0700 |
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From: Chris Wilson <chris@chris-wilson.co.uk>
The current computation, introduced with f12a15be63, of FSEC_PER_SEC using the multiplication of (FSEC_PER_NSEC * NSEC_PER_SEC) is performed only with 32bit integers on small machines, resulting in an overflow and a *very* short intervals being programmed. An interrupt storm follows.
Note that we also have to specify FSEC_PER_SEC as being long long to overcome the same limitations.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> Signed-off-by: John Stultz <johnstul@us.ibm.com> Cc: Thomas Gleixner <tglx@linutronix.de> --- arch/x86/kernel/hpet.c | 4 ++-- include/linux/time.h | 2 +- 2 files changed, 3 insertions(+), 3 deletions(-) diff --git a/arch/x86/kernel/hpet.c b/arch/x86/kernel/hpet.c index 33dbcc4..351f9c0 100644 --- a/arch/x86/kernel/hpet.c +++ b/arch/x86/kernel/hpet.c @@ -582,7 +582,7 @@ static void init_one_hpet_msi_clockevent(struct hpet_dev *hdev, int cpu) * scaled math multiplication factor for nanosecond to hpet tick * conversion. */ - hpet_freq = 1000000000000000ULL; + hpet_freq = FSEC_PER_SEC; do_div(hpet_freq, hpet_period); evt->mult = div_sc((unsigned long) hpet_freq, NSEC_PER_SEC, evt->shift); @@ -837,7 +837,7 @@ static int hpet_clocksource_register(void) * cyc/sec = FSEC_PER_SEC/hpet_period(fsec/cyc) * cyc/sec = (FSEC_PER_NSEC * NSEC_PER_SEC)/hpet_period */ - hpet_freq = FSEC_PER_NSEC * NSEC_PER_SEC; + hpet_freq = FSEC_PER_SEC; do_div(hpet_freq, hpet_period); clocksource_register_hz(&clocksource_hpet, (u32)hpet_freq); diff --git a/include/linux/time.h b/include/linux/time.h index cb34e35..1261270 100644 --- a/include/linux/time.h +++ b/include/linux/time.h @@ -38,7 +38,7 @@ extern struct timezone sys_tz; #define NSEC_PER_MSEC 1000000L #define USEC_PER_SEC 1000000L #define NSEC_PER_SEC 1000000000L -#define FSEC_PER_SEC 1000000000000000L +#define FSEC_PER_SEC 1000000000000000LL #define TIME_T_MAX (time_t)((1UL << ((sizeof(time_t) << 3) - 1)) - 1) -- 1.6.0.4
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