On Tue, 20 Nov 2018, Linus Walleij wrote: > On Mon, Nov 19, 2018 at 2:22 AM Finn Thain <fth...@telegraphics.com.au> wrote: > > > Add a platform clocksource by adapting the existing arch_gettimeoffset > > implementation. > > > > Signed-off-by: Finn Thain <fth...@telegraphics.com.au> > > Acked-by: Linus Walleij <linus.wall...@linaro.org> > > Tested-by: Stan Johnson <user...@yahoo.com> > > As noted for the Amiga CIA (which is pretty much a sibling to this MOS > 6522 VIA) this chip also has two counters and could use one as > clocksource and the other as clock event. > > Again I bet this is just using one timer out of habit. > > It will be an easy feat to make a clean clocksource+clock event for this > hardware as well once this refactoring is complete. >
Right. Both timer 1 and timer 2 have a timed interrupt mode, and either could probably serve as a clock event device or a clocksource. Some Mac models have a second VIA with two more timers, but not all. (As clock event devices, the longest interval you can program is about 83 ms. As 783360 Hz, 16-bit clocksources, they wrap about 12 times every second.) If you use one timer as a clock event device and the other as a clocksource, there are no timers left to run the existing timer_interrupt() handler. So this arrangement would require GENERIC_CLOCKEVENTS=y, right? Then, wouldn't all relevant platforms have to support GENERIC_CLOCKEVENTS=y, if a single binary was to support all of those platforms? -- > Yours, > Linus Walleij >
