On Fri, Aug 23, 2024 at 12:31:07PM +0530, subramanian.mohan@xxxxxxxxx wrote: > From: Subramanian Mohan <subramanian.mohan@xxxxxxxxx> > > Add Intel Timed I/O PPS usage instructions. > > Co-developed-by: Pandith N <pandith.n@xxxxxxxxx> > Signed-off-by: Pandith N <pandith.n@xxxxxxxxx> > Signed-off-by: Lakshmi Sowjanya D <lakshmi.sowjanya.d@xxxxxxxxx> > Reviewed-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx> > Acked-by: Rodolfo Giometti <giometti@xxxxxxxxxxxx> > Signed-off-by: Subramanian Mohan <subramanian.mohan@xxxxxxxxx> > --- > Documentation/driver-api/pps.rst | 24 ++++++++++++++++++++++++ > 1 file changed, 24 insertions(+) > > diff --git a/Documentation/driver-api/pps.rst b/Documentation/driver-api/pps.rst > index 78dded03e5d8..75f7b094f963 100644 > --- a/Documentation/driver-api/pps.rst > +++ b/Documentation/driver-api/pps.rst > @@ -246,3 +246,27 @@ delay between assert and clear edge as small as possible to reduce system > latencies. But if it is too small slave won't be able to capture clear edge > transition. The default of 30us should be good enough in most situations. > The delay can be selected using 'delay' pps_gen_parport module parameter. > + > + > +Intel Timed I/O PPS signal generator > +------------------------------------ > + > +Intel Timed I/O is a high precision device, present on 2019 and newer Intel > +CPUs, that can generate PPS signals. > + > +Timed I/O and system time are both driven by same hardware clock. The signal > +is generated with a precision of ~20 nanoseconds. The generated PPS signal > +is used to synchronize an external device with system clock. For example, > +it can be used to share your clock with a device that receives PPS signal, > +generated by Timed I/O device. There are dedicated Timed I/O pins to deliver > +the PPS signal to an external device. > + > +Usage of Intel Timed I/O as PPS generator: > + > +Start generating PPS signal:: > + > + $echo 1 > /sys/devices/platform/INTCxxxx\:00/enable > + > +Stop generating PPS signal:: > + > + $echo 0 > /sys/devices/platform/INTCxxxx\:00/enable As I mentioned on the sysfs documentation, why isn't this just a generic pps class attribute instead? Why did you make it only-this-one-special-driver type of thing? thanks, greg k-h
