[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)

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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=205458

--- Comment #6 from Mark Millard <markmi at dsl-only.net> ---
(In reply to Mark Millard from comment #5)

Jukka A. Ukkonen has reported Nathan Whithorns patch to have failed to work but
my hack to have worked:

In https://lists.freebsd.org/pipermail/freebsd-ppc/2016-September/008416.html
he reports the failure of Nathan's patch. . .

I just tried the patch on a PowerMac G5 early 2005
model ...

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>

which I think is a PowerMac7,3. It still panics right
after it has reported VT(ofwfb).

--jau


But we had an E-mail exchange about him manually applying a simple edit to get
my patch and he reports in the end. . .

I rebooted the box only a few minutes ago, and this
time it booted just fine.
Well, the tmpfs has started failing as follows...

# mount /tmp
mount: tmpfs: Operation not supported by device

but supposedly this is an unrelated issue. At least I hope so. ;-)

Now the function reads as shown below, and I guess this is
exactly what you had in mind.

static __inline void
ofw_sprg_prepare(void)
{
       if (ofw_real_mode)
               return;

       /*
        * Assume that interrupt are disabled at this point, or
        * SPRG1-3 could be trashed
        */
       __asm __volatile("mfsprg0 %0\n\t"
                        "mtsprg1 %1\n\t"
                        "mtsprg2 %2\n\t"
                        "mtsprg3 %3\n\t"
                        : "=&r"(ofw_sprg0_save)
                        :
                        "r"(ofmsr[2]),
                        "r"(ofmsr[3]),
                        "r"(ofmsr[4]));
}

So, from my point of view the PowerMac7,3 seems to be back to
relative health with this change. I hope it works for all the
other G5s as well.

--jau

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