RE: [PATCH] powerpc:Fix rheap alignment problem

[Li Yang-r58472]

> > > Two problems with genalloc that I can see (for CPM programming):
> > > 1) (minor) Does not have a way to specify alignment (genalloc does it for
> you)
> > > 2) (major problerm, at least for me) Does not have a way to allocate a
> specified address in the pool.
> > >
> > > 2 is needed esp when programming MCC drivers, since a lot of the
> datastructures must be in DP RAM _and_ be in a specific spot. And if you cannot
> tell the allocator that I am using a specific address, then the allocator might
> very well give somebody else that portion of RAM. The only solution without
> a fixed allocator is to allocate ALL memory in the DP RAM and use your own
> allocator.
> > >
> >
> > Yeah, that too.
> >
> > Too bad there are no main tree drivers like that, but they do exist.
> >
> > One could conceivably hack genalloc to do that, but will end up with
> > something complex too.
> >
> > BTW, there are other uEngine based architectures with similar alignment
> > requirements.
> >
> > So in conclusion, for the in-tree drivers genalloc is sufficient as an cpm
> memory allocator.
> > For some out of tree drivers, it is not.
> 
> Sounds like a good enough justification to keep rheap for now then.

As the reason I stated in the last mail, rheap should continue being used not only for this fix-address situation but also for CPM/QE buffer descriptor management.  Rheap and genalloc are two different implementations of dynamic memory allocator, which have different suitable cases.  Both of them should be kept for different applications.
> 
> Ben.

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