G5 fan problems return moving to 2.6.15 with dual processor 2.7GHz machine

[Brian D. Carlstrom]

Benjamin Herrenschmidt writes:
 > prom_printf should work ... try booting manually (from the OF command
 > line) and maybe comment out the code that opens the displays... (it
 > may be clearing the screen)....

I tried commented out prom_check_displays and that does prevent the
clearing of the screen, but still no visible prom_printf output. The
last output seems to be from yaboot, its certainly not one of the
prom_print messages from prom_init.c. For good measure, I also tried
adding "video=ofonly". Still no prom_printf output visible.

However, when I rebooted back to my 2.6.14 kernel, I saw the usual
prom_printf messages from prom_init without any changes. I reviewed the
prom_init.c diffs between 2.6.14 and 2.6.15 but they are large enough
that its not easy to spot an obvious problem.

In any case, I didn't have much time to really look at this today, just
enough to try the disabling prom_check_displays, I'll have to look more
Friday.

-bri