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Date:      Tue, 13 Sep 2016 01:45:26 -0700
From:      Mark Millard <markmi@dsl-only.net>
To:        jau789@gamil.com
Cc:        FreeBSD PowerPC ML <freebsd-ppc@freebsd.org>, Nathan Whitehorn <nwhitehorn@freebsd.org>
Subject:   Re: [Bug 205458] 11.0-CURRENT/10-STABLE powerpc64: a PowerMac G5 specific sys/powerpc/ofw/ofw_machdep.c change for reliable PowerMac G5 booting (with lots of RAM)
Message-ID:  <8A406E69-0C88-47B9-97BB-9E07561A8139@dsl-only.net>

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Jukka A. Ukkonen jau789 at gmail.com  wrote on Tue Sep 13 08:03:38 UTC =
2016 :

> On 09/13/16 09:31, bugzilla-noreply at freebsd.org wrote:
> > https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D205458
> >=20
> > --- Comment #5 from Mark Millard <markmi at dsl-only.net> ---
> > Nathan Whitehorn has put out a kernel patch that he is asking for =
help with
> > testing on PowerMac/iMac G5 variations. See:
> >=20
> > =
https://lists.freebsd.org/pipermail/freebsd-ppc/2016-September/008413.html=

> >=20
> > The patch is not just using __powerpc64__ instead of =
POWERMAC_G5_SPECIFIC_BUILD
> > in my presentation of my hack.
> >=20
> > Nathan has already tested a PowerMac11,2.
> >=20
> > If anyone reading this has any other type(s) of Apple G5's and is =
willing/able
> > it would be good to get in some testing before the change is made to =
the
> > kernel.
> >=20
> > I expect that it does not mater much which version/variation of =
10.x, 11.0, or
> > 12 is used if the original boot problems can sometimes be observed =
before the
> > change. Although I'm not sure of the patch automatically applies =
nicely to all
> > possible vintages of those.
> >=20
> >=20
> > As for me. . .
> >=20
> > It will be a few weeks before I'll again have access in order to =
test a
> > PowerMac7,2 (or to independently repeat PowerMac11,2 testing). I'll =
not have
> > access to other Apple G5's. So my range of testing will be rather =
limited and
> > will not be soon.
> >=20
>=20
> I just tried the patch on a PowerMac G5 early 2005
> model ...
>=20
> cpu0: IBM PowerPC 970 revision 2.2, 2000.19 MHz
> cpu0: Features dc000000<PPC32,PPC64,ALTIVEC,FPU,MMU>
> cpu0: HID0 511081<NAP,DPM,NHR,TBEN,ENATTN>
>=20
> which I think is a PowerMac7,3. It still panics right
> after it has reported VT(ofwfb).
>=20
> --jau

[Be warned that it has been since early June since I've done any =
on-powerpc activity. My memory need not be correct or complete enough =
and I do not have the context to cross-check myself at this time.]

I build world and kernel from source and build the kernel to have sc and =
vt present (and PS3 disabled in order to allow that) but I only use sc =
for the larger display that I sometimes use (2560x1440 as I remember).

[Note: I've only used console mode for a long time. I've no clue if X11 =
is even still possible via the ports. Although that also might get into =
which video card is present. Someday I'll probably try that again.]

If I remember right this sc-only use is because things did not work well =
for vt with that large of display (last that I tried). But I do not =
remember just where/how it stopped/failed. (I could be confusing an =
older memory with more modern behavior to some extent.) At one time =
there was an unchecked memory buffer overrun for console use for such =
large screens, at least in some 10.x variant for at least one of vt vs. =
sc.

That background information means that "after it has reported VT(ofwfb)" =
leads me to wonder if a vt/screen-size related issue might be involved.


Another testing option (other than screen size variations) would be to =
try my hack instead of Nathan's code. (I expect the same result. But if =
not then that result would be interesting.) That change from =
original/offcial source would be the deletion of

     "mtsprg0 %1\n\t"
and
     "r"(ofmsr[1]),

from:

> 	__asm __volatile("mfsprg0 %0\n\t"
> 			 "mtsprg0 %1\n\t"
> 			 "mtsprg1 %2\n\t"
> 			 "mtsprg2 %3\n\t"
> 			 "mtsprg3 %4\n\t"
> 			 : "=3D&r"(ofw_sprg0_save)
> 			 : "r"(ofmsr[1]),
> 			 "r"(ofmsr[2]),
> 			 "r"(ofmsr[3]),
> 			 "r"(ofmsr[4]));

in sys/powerpc/ofw/ofw_machdep.c .



=3D=3D=3D
Mark Millard
markmi at dsl-only.net




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