[Ksummit-discuss] [TECH TOPIC] mobile phones
Sebastian Reichel
sre at kernel.org
Sun Jul 2 12:03:21 UTC 2017
Hi,
On Wed, Jun 28, 2017 at 10:27:22PM +0200, Pavel Machek wrote:
> > > Oh, another major piece is DSP coprocessor that is there. Unlike
> > > graphics, we don't even know how support for it should like.
> >
> > https://www.kernel.org/doc/Documentation/remoteproc.txt
> >
> > config OMAP_REMOTEPROC
> > tristate "OMAP remoteproc support"
> > [...]
> > help
> > Say y here to support OMAP's remote processors (dual M3
> > and DSP on OMAP4) via the remote processor framework.
> >
> > Currently only supported on OMAP4.
> >
> > Usually you want to say Y here, in order to enable multimedia
> > use-cases to run on your platform (multimedia codecs are
> > offloaded to remote DSP processors using this framework).
> >
> > It's safe to say N here if you're not interested in multimedia
> > offloading or just want a bare minimum kernel.
> >
> > I have been told by some Nokia people (I do not remember who it
> > was, possibly Sakari), that the DSP is not that powerful and any
> > calculation should also be possible on CPU (wasting a bit of
> > energy).
>
> Ok, we probably don't care about DSP, but lets say we had really
> fast DSP or really cared about power.
>
> We'd need remoteproc. Sure. But that has no interface for userland,
> right?
remoteproc is only for start/stop + fw loading. The actual
communication is done using rpmsg, which does not yet have a
userspace API afaik.
> So we'd need to introduce interface for userland... fine.
>
> And then we'd need cross-compilers for the DSP used. Ok.
Yes. As far as I know there is currently no open source toolchain
for the TI DSP.
> And then we'd need to split mpg123 to CPU and DSP parts, and modify it
> so that it can run the DSP parts using remoteproc, when available?
>
> That starts to be ... complex, with changes all over the system :-(.
With little gain expected on N900...
-- Sebastian
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