[PATCH v3 14/15] ARM: vexpress/dcscb: handle platform coherency exit/setup and CCI

[Lorenzo Pieralisi]

On Tue, Jan 29, 2013 at 06:42:33PM +0000, Nicolas Pitre wrote:
> On Tue, 29 Jan 2013, Lorenzo Pieralisi wrote:
> 
> > On Tue, Jan 29, 2013 at 07:51:09AM +0000, Nicolas Pitre wrote:
> > 
> > [...]
> > 
> > > +		/*
> > > +		 * Flush the local CPU cache.
> > > +		 *
> > > +		 * A15/A7 can hit in the cache with SCTLR.C=0, so we don't need
> > > +		 * a preliminary flush here for those CPUs.  At least, that's
> > > +		 * the theory -- without the extra flush, Linux explodes on
> > > +		 * RTSM (maybe not needed anymore, to be investigated).
> > > +		 */
> > > +		flush_cache_louis();
> > 
> > This is not needed. If it is, that is a model bug and should be flagged
> > up as such.
> 
> Could someone at ARM do that?

I will do that.

> 
> I just confirmed that this is still the case by commenting out the 
> preliminary flush calls and hot-plugging CPUs out and back.  Result is a 
> non-sensical kernel oops which has the looks of serious memory 
> corruption.  This is with RTSM version 7.1.42.
> 
> > > +		cpu_proc_fin(); /* disable allocation into internal caches*/
> > 
> > This code disables the I-cache causing following instruction fetches from
> > DRAM; that is extremely slow and should be avoided, there is no point in
> > disabling the I-cache here, that is not required.
> > On fast-models that's a non-issue, but I really want to prevent copy'n'paste
> > of this sequence as it stands.
> 
> Agreed, I'll change that.  The (not included in this series) TC2 backend 
> does leave the I-cache active already.

Great, thanks !!

Lorenzo