RE: [PATCH 01/17] PM: fix suspend control for IVA2

Artem Bityutskiy
2009-10-23T05:22:12Z

On Thu, 2009-10-22 at 16:21 -0500, Woodruff, Richard wrote:
> > From: linux-omap-owner@vger.kernel.org [mailto:linux-omap-
> > owner@vger.kernel.org] On Behalf Of Paul Walmsley
> > Sent: Thursday, October 22, 2009 5:24 AM
>
> > > IVA2 controls its target power state individually, thus suspend should not
> > > touch IVA2. Without this patch DSP suspend always fails.
> >
> > We don't allow other device drivers to touch PRCM bits, so we should
> > probably should remove all PRCM register accesses from the DSPBridge code,
> > so all power control should go through the ARM.
> >
> > Is there a reason why the ARM code can't handle the DSP powerdomain?
>
> Sharing with DSP is something which probably could use some improvement.
>
> Today DSP self-manages its domain. Its (bios) micro-kernel makes decisions to optimize its domain. The ARM can't really micro-manage the DSP as he doesn't even want to know at the detail level what the DSP is up to at every instant.
>
> - During idle time cpuidle should just be checking dsp status to see if its current state gets in the way of a low c-state.
>
> - bridge does register with suspend frame work so he should do the right thing when in the system.
>
> * problem is when bridge isn't there what to do. This is especially after an unload of the bridge.

Just a side note reminder: bridge does not exist in the real world.

[dedekind@sauron linux-omap-2.6]\$ ls drivers/dsp/bridge
ls: cannot access drivers/dsp/bridge: No such file or directory

--
Best Regards,
Artem Bityutskiy (Артём Битюцкий)

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