> -----Original Message----- > From: Richard Cochran [mailto:richardcoch...@gmail.com] > Sent: Tuesday, April 07, 2015 10:33 PM > To: Keller, Jacob E > Cc: linuxptp-devel@lists.sourceforge.net > Subject: Re: [Linuxptp-devel] timecounter mask for non-bitwise > overflowing? > > On Tue, Apr 07, 2015 at 11:28:40PM +0000, Keller, Jacob E wrote: > > > So, I guess you want to do this because your HW has this split > > > representation, but you cannot adjust the frequency? > > > > Several reasons: > > > > 1) consistency with the rest of the hardware in the driver > > 2) atomic time increments (I have a patch I want to propose that will > enable atomic time increment for timecounters by just adding or subtracting > from the offset) > > We have this already. See 796c1ef in v4.0-rc1.
Yep I didn't notice this yet, but when I was looking at the code I thought of it. I'll get it implemented then :) > > > 3) hardware may have to change the frequency of the clock driving the > system timer, so even though it was supposed to represent nominal seconds > and nanoseconds, it won't actually, since the underlying clock won't be > running at the right frequency). > > 4) support the gettime64/settime64 routines via the timecounter. > > Of course, the big disadvantage of using timecounter is that it makes > it difficult or impossible to use hardware features like periodic > output signals or external time stamps. > Yea. The problem is that I pretty much can't use those anyways if the hardware frequency is incorrect, (which regrettably in this case it is). > > > 32 bits of seconds gives you 136 years of uptime (assuming the counter > > > starts at zero). You can just use a 64 bit mask and forget about the > > > overflow, since it can never happen in practice. > > > > > > > Ok. That's what I was thinking. I would prefer that it not happen at all, > > but > it really is a non-issue as you said. > > IMHO an uptime range of 136 years is reasonable, but you should > document the actual range of possibilities according to the > frequencies you mentioned. Ofcourse. Thanks for the help. > > Thanks, > Richard ------------------------------------------------------------------------------ BPM Camp - Free Virtual Workshop May 6th at 10am PDT/1PM EDT Develop your own process in accordance with the BPMN 2 standard Learn Process modeling best practices with Bonita BPM through live exercises http://www.bonitasoft.com/be-part-of-it/events/bpm-camp-virtual- event?utm_ source=Sourceforge_BPM_Camp_5_6_15&utm_medium=email&utm_campaign=VA_SF _______________________________________________ Linuxptp-devel mailing list Linuxptp-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linuxptp-devel
