[PATCH 1/2] Add support for stopping spus from xmon

Michael Ellerman michael at ellerman.id.au
Wed Oct 18 17:16:33 EST 2006

On Thu, 2006-10-12 at 20:10 -0700, Haren Myneni wrote:
> Michael Ellerman wrote:
> >This patch adds support for stopping, and restarting, spus
> >from xmon. We use the spu master runcntl bit to stop execution,
> >this is apparently the "right" way to control spu execution and
> >spufs will be changed in the future to use this bit.
> >
> >Testing has shown that to restart execution we have to turn the
> >master runcntl bit on and also rewrite the spu runcntl bit, even
> >if it is already set to 1 (running).
> >
> >Stopping spus is triggered by the xmon command 'ss' - "spus stop"
> >perhaps. Restarting them is triggered via 'sr'. Restart doesn't
> >start execution on spus unless they were running prior to being
> >stopped by xmon.
> >
> >Walking the spu->full_list in xmon after a panic, would mean
> >corruption of any spu struct would make all the others
> >inaccessible. To avoid this, and also to make the next patch
> >easier, we cache pointers to all spus during boot.
> >
> >We attempt to catch and recover from errors while stopping and
> >restarting the spus, but as with most xmon functionality there are
> >no guarantees that performing these operations won't crash xmon
> >itself.
> >
> >  
> >
> I think, kdump also need stop_spus() functionality when the dump support 
> is included on cell. If so, how about both stop_spus() and start_spus() 
> in platforms/cell/.

Good point. We haven't got that far with kdump on cell so I hadn't
thought of it. We won't need start_spus(), but we will need something to
stop spus for kdump. I'll leave it for now, but keep it in mind for when
we get kdump going on cell.


Michael Ellerman
OzLabs, IBM Australia Development Lab

wwweb: http://michael.ellerman.id.au
phone: +61 2 6212 1183 (tie line 70 21183)

We do not inherit the earth from our ancestors,
we borrow it from our children. - S.M.A.R.T Person
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