recent FreeBSD 13.0-CURRENT has fans screaming again on PowerMac quad

[Justin Hibbits]

On Fri, Jun 19, 2020, 17:58 Mark Millard <marklmi at yahoo.com> wrote:

>
>
> On 2020-Jun-19, at 07:34, Justin Hibbits <chmeeedalf at gmail.com> wrote:
>
> >> . . .
> >
> > If it's SMP timebase sync related, the problem actually looks
> > relatively easy to solve, at least for G4 and PowerMac11,2 G5's
> > (PowerMac7,3 looks trickier), from examining the Linux source and the
> > OFW device tree.  The PowerMac11,2 (which the Quad is), and the G4s,
> > use a GPIO to disable and enable the timebase, so a very similar thing
> > can be done with the powermac platform driver as is done with the
> > mpc85xx platform driver, which effectively is:
> >
> >  All CPUs rendezvous in the smp_timebase_sync() function
> >  BSP disables timebase, sets the timebase sync to non-zero
> >  APs check for non-zero timebase, set their timebases to it
> >  All CPUs rendezvous at the end
> >  BSP re-enables timebase, and unleashes CPUs
> >
> > A couple hours of work for someone with the hardware, I'd say.  I can
> > probably provide a patch to be tested by someone in the next few days,
> > if someone else doesn't get around to it first.
> >
>
> I look forward to seeing how some of the 4 uses
> of platform_smp_timebase_sync ends up being
> adjusted/replaced/removed/... :
>
> static void cpu_mp_unleash(void *dummy) does:
> platform_smp_timebase_sync(ap_timebase, 0)
>        void machdep_ap_bootstrap(void)  does:
> platform_smp_timebase_sync(ap_timebase, 1)
>        void cpu_sleep()                 does:
> platform_smp_timebase_sync(timebase, 0)
>        void cpudep_ap_setup()           does:
> platform_smp_timebase_sync(0, 1)
>
> (That last has a comment reporting: /* The following is needed for
> restoring from sleep. */)
>

The cpu_sleep() one is covered by D23828, since that is mpc745x specific,
and the cpudep_ap_setup() will likely follow that.



> Hopefully I'll learn some of what I did not figure out
> in other respects as well.
>
>
> ===
> Mark Millard
> marklmi at yahoo.com
> ( dsl-only.net went
> away in early 2018-Mar)
>

- Justin

>