FrontRunner/Toucan-AF: work around AGESA RAM init crashing on reboot

If you try to reset the system with outb(3,0x92), outb(4,0xcf9) or a
triple-fault it will instead crash with a messy screen.  As the more common
outb(0xFE, 0x64) doesn't work with our setup, Linux will crash whenever you
ask it to reboot.  Closer inspection shows that on a warm boot of Coreboot
agesawrapper_amdinitpost() always fails with error code 7.  Looks like DDR3
re-init goes wrong somehow.  I tried find the reason for this but was
unable to.  I am convinced this is not board specific but a bug in AGESA.

In the end I had to settle for a workaround:  if amdinitpost returns 7 this
patch resets the system harder with outb(0x06, 0x0cf9), after that RAM init
will succeed.  As amdinitpost is early in POST this automatic reset is
quick enough not to be noticable.

I'd perfer a real fix, but that's all I have.

Change-Id: I4763254b489f42a135232e45328ecf0d5c4d961a
Signed-off-by: Jens Rottmann <JRottmann@LiPPERTembedded.de>
Reviewed-on: http://review.coreboot.org/2573
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
2 files changed