On Fri, Mar 23, 2018 at 11:03:50AM -0500, Alex Fontaine wrote: > The kernel documentation states the ability to use POSIX timers with the PTP > hardware clocks. This does not appear to be implemented in the ptp > subsystem drivers. What is preventing this timer interface from being > implemented?
See below. > Previous discussions[1] indicate the PHC timer functionality was less > effective than using nanosleep with the system clock for driving a gpio. That is your answer. > However, the timers are still useful if they trigger a hardware event. For > example, user software configures a timer on a PHC, the timer fires both an > event in hardware to be used by external hardware and a notification back to > the user. That event to external hardware would occur precisely from the > phc time. The user would be notified of the event via the timer interface. Just set a hrtimer to expire at the same time, or just before the deadline. > The latency from software responding to the timer and then firing an event > on a gpio would be eliminated. No, the latency increases when using PHC. That is the whole point. Thanks, Richard ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ Linuxptp-devel mailing list Linuxptp-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linuxptp-devel
