On Fri, Sep 09, 2022 at 07:32:58AM -0500, Scott Cheloha wrote: > On Fri, Sep 09, 2022 at 03:59:01PM +1000, Jonathan Gray wrote: > > On Thu, Sep 08, 2022 at 08:31:21PM -0500, Scott Cheloha wrote: > > > On Sat, Aug 27, 2022 at 09:28:06PM -0500, Scott Cheloha wrote: > > > > Whoops, forgot about the split read problem. My mistake. > > > > > > > > Because 32-bit platforms cannot do bus_space_read_8 atomically, and > > > > i386 can use acpihpet(4), we can only safely use the lower 32 bits of > > > > the counter in acpihpet_delay() (unless we want two versions of > > > > acpihpet_delay()... which I don't). > > > > > > > > Switch from acpihpet_r() to bus_space_read_4(9) and accumulate cycles > > > > as we do in acpihpet_delay(). Unlike acpitimer(4), the HPET is a > > > > 64-bit counter so we don't need to mask the difference between val1 > > > > and val2. > > > > > > > > [...] > > > > > > 12 day ping. > > > > > > This needs fixing before it causes problems. > > > > the hpet spec says to set a bit to force a 32-bit counter on > > 32-bit platforms > > > > see 2.4.7 Issues related to 64-bit Timers with 32-bit CPUs, in > > https://www.intel.com/content/dam/www/public/us/en/documents/technical-specifications/software-developers-hpet-spec-1-0a.pdf > > I don't follow your meaning. Putting the HPET in 32-bit mode doesn't > help us here, it would just break acpihpet_delay() in a different way. > > The problem is that acpihpet_delay() is written as a 64-bit delay(9) > and there's no way to do that safely on i386 without introducing extra > overhead. > > The easiest and cheapest fix is to rewrite acpihpet_delay() as a > 32-bit delay(9), i.e. we count cycles until we pass a threshold. > acpitimer_delay() in acpi/acpitimer.c is a 32-bit delay(9) and it > works great, let's just do the same thing again here. > > ok?
Seems to handle wrapping. ok jsg@ > > Index: acpihpet.c > =================================================================== > RCS file: /cvs/src/sys/dev/acpi/acpihpet.c,v > retrieving revision 1.28 > diff -u -p -r1.28 acpihpet.c > --- acpihpet.c 25 Aug 2022 18:01:54 -0000 1.28 > +++ acpihpet.c 9 Sep 2022 12:29:41 -0000 > @@ -281,13 +281,19 @@ acpihpet_attach(struct device *parent, s > void > acpihpet_delay(int usecs) > { > - uint64_t c, s; > + uint64_t count = 0, cycles; > struct acpihpet_softc *sc = hpet_timecounter.tc_priv; > + uint32_t val1, val2; > > - s = acpihpet_r(sc->sc_iot, sc->sc_ioh, HPET_MAIN_COUNTER); > - c = usecs * hpet_timecounter.tc_frequency / 1000000; > - while (acpihpet_r(sc->sc_iot, sc->sc_ioh, HPET_MAIN_COUNTER) - s < c) > + val2 = bus_space_read_4(sc->sc_iot, sc->sc_ioh, HPET_MAIN_COUNTER); > + cycles = usecs * hpet_timecounter.tc_frequency / 1000000; > + while (count < cycles) { > CPU_BUSY_CYCLE(); > + val1 = val2; > + val2 = bus_space_read_4(sc->sc_iot, sc->sc_ioh, > + HPET_MAIN_COUNTER); > + count += val2 - val1; > + } > } > > u_int > >