Re: [PATCH] clocksource_cyc2ns: avoid overflowing 64 bits

2016-11-16 Thread Chris Metcalf
On 11/16/2016 2:45 PM, John Stultz wrote: On Wed, Nov 16, 2016 at 11:30 AM, Chris Metcalf wrote: diff --git a/include/linux/clocksource.h b/include/linux/clocksource.h index 08398182f56e..529884b8 100644 --- a/include/linux/clocksource.h +++ b/include/linux/clocksource.h @@ -171,6 +171,10 @

Re: [PATCH] clocksource_cyc2ns: avoid overflowing 64 bits

2016-11-16 Thread Chris Metcalf
On 11/16/2016 1:04 PM, John Stultz wrote: On Wed, Nov 16, 2016 at 8:57 AM, Chris Metcalf wrote: include/linux/clocksource.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/include/linux/clocksource.h b/include/linux/clocksource.h index 08398182f56e..b2a022acf232 100644 --

Re: [PATCH] clocksource_cyc2ns: avoid overflowing 64 bits

2016-11-16 Thread Chris Metcalf
On 11/16/2016 3:00 PM, John Stultz wrote: On Wed, Nov 16, 2016 at 11:56 AM, Chris Metcalf wrote: On 11/16/2016 2:45 PM, John Stultz wrote: On Wed, Nov 16, 2016 at 11:30 AM, Chris Metcalf wrote: diff --git a/include/linux/clocksource.h b/include/linux/clocksource.h index 08398182f56e..529

Re: [PATCH] clocksource_cyc2ns: avoid overflowing 64 bits

2016-11-16 Thread John Stultz
On Wed, Nov 16, 2016 at 11:56 AM, Chris Metcalf wrote: > On 11/16/2016 2:45 PM, John Stultz wrote: >> >> On Wed, Nov 16, 2016 at 11:30 AM, Chris Metcalf >> wrote: >>> >>> diff --git a/include/linux/clocksource.h b/include/linux/clocksource.h >>> index 08398182f56e..529884b8 100644 >>> --- a/i

Re: [PATCH] clocksource_cyc2ns: avoid overflowing 64 bits

2016-11-16 Thread John Stultz
On Wed, Nov 16, 2016 at 11:30 AM, Chris Metcalf wrote: > diff --git a/include/linux/clocksource.h b/include/linux/clocksource.h > index 08398182f56e..529884b8 100644 > --- a/include/linux/clocksource.h > +++ b/include/linux/clocksource.h > @@ -171,6 +171,10 @@ static inline u32 clocksource_hz2

Re: [PATCH] clocksource_cyc2ns: avoid overflowing 64 bits

2016-11-16 Thread John Stultz
On Wed, Nov 16, 2016 at 11:30 AM, Chris Metcalf wrote: > On 11/16/2016 1:04 PM, John Stultz wrote: >> >> On Wed, Nov 16, 2016 at 8:57 AM, Chris Metcalf >> wrote: >>> >>> include/linux/clocksource.h | 2 +- >>> 1 file changed, 1 insertion(+), 1 deletion(-) >>> >>> diff --git a/include/linux/clo

Re: [PATCH] clocksource_cyc2ns: avoid overflowing 64 bits

2016-11-16 Thread John Stultz
On Wed, Nov 16, 2016 at 8:57 AM, Chris Metcalf wrote: > For large values of "mult" and long uptimes, the intermediate > result of "cycles * mult" can overflow 64 bits. For example, > the tile platform uses this helper function; for a 1.2 GHz clock, > we have mult = 853, and after 208.5 days, we o