Sequoia kernel crash workaround.

[Josh Boyer]

On Thu, 20 Sep 2007 12:32:56 -0500 (CDT)
Milton Miller <miltonm at bga.com> wrote:

> On Fri Sep 21 02:56:32 EST 2007, Valentine Barshak wrote:
> > Josh Boyer wrote:
> >> On Wed, 19 Sep 2007 14:30:24 -0500
> >> Olof Johansson <olof at lixom.net> wrote:
> >> 
> >>> On Wed, Sep 19, 2007 at 09:19:47PM +0200, Stefan Roese wrote:
> >>>> Hi Valentine,
> >>>>
> >>>> On Wednesday 19 September 2007, Valentine Barshak wrote:
> >>>>> Disabling write pipelining really helps.
> >>>>> Josh, David, what is the right place to put this workaround to?
> >>>>>
> >>>>> Is it OK to do mtdcr(PLB4A0_ACR, mfdcr(PLB4A0_ACR) & ~PLB4_WRP); in
> >>>>> arch/powerpc/boot/cuboot-sequoia.c:sequoia_fixups()?
> >>>>> or
> >>>>> should this be done in
> >>>>> arch/powerpc/platforms/44x/sequoia.c:sequoia_setup_arch()
> >>>>> with dcr_map, dcr_read/write stuff?
> >>>> I vote for putting it into sequoia.c, since it's very likely to happen that 
> >>>> Sequoia will at one point be booted without the bootwrapper. Or perhaps it 
> >>>> should go into some common code checking the PVR and disabling it when this 
> >>>> 440EPx/GRx is detected, since all those boards are affected.
> >>> This is what we have setup_cpu functions in the cpu table for. Please
> >>> put it there instead of in board code.
> >> 
> >> Yes, agreed.
> > 
> > I was thinking about it. Looks like it's the best place, but the code 
> > that actually calls setup_cpu is under ifdef CONFIG_PPC64, while lots of 
> > cpu_setup functions are defined for ppc32 processors.
> > Is it OK to remove this ifdef, or should I do CONFIG_PPC64 || CONFIG_44x?
> 
> head_32.S calls call_setup_cpu in misc_32.S to call the cpu setup functon.
> 
> Note that these functions are called before the kernel is copied down to
> 0, so on ppc32 you will need the PTRRELOC type stuff.  Also the callsite
> implies that the cpu number is available in r24, which may or may not be
> true when called from C.
> 
> Its probably easier to just call call_setup_cpu in the other 32 bit 
> head_xxx files.

Hm.  I'll have to see how well that would work for 4xx.  Seems 8xx and
FSL BookE are in a similar situation.

josh