[PATCH V2] ARM: dove: dt: revert PMU interrupt controller node

[Russell King - ARM Linux]

On Mon, Mar 03, 2014 at 06:37:40PM +0100, Andrew Lunn wrote:
> On Mon, Mar 03, 2014 at 03:02:15PM +0000, Russell King - ARM Linux wrote:
> > On Mon, Feb 17, 2014 at 08:00:36PM +0000, Jason Cooper wrote:
> > > The corresponding driver didn't make it into v3.14, so we need to remove
> > > the node.  Dove systems fail to boot with the node present and no
> > > driver.
> > > 
> > > This node will be re-added when the driver makes it to mainline.
> > 
> > I'm going to stick my oar in on this and ask what is a very fundamental
> > question.
> > 
> > If we're adding the PMU interrupt controller as a separate "device"
> > aren't we describing our implementation rather than the hardware?  It
> > isn't a separate device as far as the description of it in the reference
> > manuals.
> > 
> > Moreover, should the PMU interrupt controller be something which is
> > handled by a separate chunk of code to a driver for the PMU as a whole,
> > or are we storing up problems with resource clashes?  I can quite see
> > a PMU driver coming along in the future offering a pair of generic
> > power domains for the GPU and VPU, and such a driver would need to map
> > all the PMU registers so it can access the power control, reset and
> > isolator registers.
> 
> Hi Russell
> 
> I suspect you are right, we are storing up problems.
> 
> During the 4 months between submitting this driver and actually
> getting it accepted, i've learned quite a bit. I tried to implement
> cpufreq for Dove and ran into the problems you mention. The registers
> in the PMU are interleaved so that you cannot cleanly separate out the
> range needed for cpufreq. We probably need a PMU device, which exports
> a register syscon and have the interrupt controller make use of it.

I know it's a pain to say this, but maybe we should hold off with the
PMU IRQ controller patch for a while longer until we get a proper idea
of what we're doing with the PMU?

If you have a look at my "Generic PM domains - too noisy?" email earlier
today on LAKML, you can see some of the code I'm talking about above - I
have that running at the moment on my CuBox.  I'm going to be doing some
power measurements soon with various different autosuspend delays to see
what effect it has.

If we do end up with a PMU driver, then I think that unless there's a
real need, it should just integrate things like the PM domains, IRQ
controller and maybe (depending on how complex it is) the cpufreq bits.
MFD is all very well, but I feel that sometimes it brings along
additional complexity at times when that complexity isn't needed.

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