Date: Fri, 19 Jun 2020 15:58:09 -0700 From: Mark Millard <marklmi@yahoo.com> To: Justin Hibbits <chmeeedalf@gmail.com> Cc: Michael Tuexen <tuexen@freebsd.org>, freebsd-ppc <freebsd-ppc@freebsd.org> Subject: Re: recent FreeBSD 13.0-CURRENT has fans screaming again on PowerMac quad Message-ID: <83F454AC-463D-4FC5-9CBE-C6166F5A9651@yahoo.com> In-Reply-To: <20200619093447.469d669c@titan.knownspace> References: <250e4677-c442-3b41-5796-6b79b07ac12c@blastwave.org> <1692AB48-2438-4B4B-82BB-F8BAEF04B459@freebsd.org> <20200619093447.469d669c@titan.knownspace>
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On 2020-Jun-19, at 07:34, Justin Hibbits <chmeeedalf at gmail.com> =
wrote:
>> . . .
>=20
> 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:
>=20
> 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
>=20
> 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.
>=20
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. */)
Hopefully I'll learn some of what I did not figure out
in other respects as well.
=3D=3D=3D
Mark Millard
marklmi at yahoo.com
( dsl-only.net went
away in early 2018-Mar)
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