[RFC 00/14] Generic clk for Orion platforms.

[Andrew Lunn]

On Tue, Mar 06, 2012 at 10:58:40AM -0500, Jason wrote:
> On Tue, Mar 06, 2012 at 07:30:56AM +0100, Andrew Lunn wrote:
> > This patch set starts the process of changing Orion based platforms to
> > use the generic clk framework. The first patch fixes compile problems
> > with the framework, and is expected to be dropped once fixed upstream.
> > Then clks are added. This is a fixed rate clk for tclk and for
> > kirkwood, most of the gated clocks also get a clk. The following
> > patches then modified the drivers to make use of these clocks,
> > getting, prepareing, enabling at probe time, and disableing,
> > unprepareing, and putting at remove time. Rather than pass the clock
> > frequency as platform_data, the driver now uses clk_get_rate(). This
> > results in some platform_data structures becoming redundant, and so
> > are removed.
> 
> Awesome, thanks for posting!
> 
> > TODO:
> > 
> >  0) Cleanup the white space changes, and hunks in the wrong patches.
> 
> It would be helpful to break out code cleanup as well.  eg spi_clock_fix
> removal, sound platform data removal, and anything else I didn't see on
> initial read through.

I could move these out, but they actually help you. It means there is
less for you to add DT support for. If they are left in, you need to
add a DT property for spi_clock_fix, etc.
 
> >  1) PCIe needs adopting to use clks.
> >  2) Strip out all references to kirkwood_clk_ctrl
> >  3) Find a solution for turning off unused clks - Probably needs
> >     framework support, which Mike has already suggested.
> 
> I'm assuming the driver(s) will increment a reference, so when it
> reaches zero, the framework would call a clk_gate hook.

You missed an important point. No driver has claimed these, but u-boot
has turned them on. So we want linux to turn off all clocks for which
there is no driver using them, in order to save power.
kirkwood_clk_ctrl is dual purpose. It turns on needed clocks, but it
also turns off unneeded clocks.
 
> >  4) Find a solution for tuning off unused SATA and PCIe PHYs. Maybe
> >     use the unprepare() method, but the current basic clk providers 
> >     don't support this.
> 
> It looks like each SATA and PCIe PHY has it's own clock and it's own
> shutdown (kirkwood_clock_gate()).  If the return value of unprepare
> indicated a clock was gated (all references gone), then the driver could
> shut down the PHY.  Or, am I missing something?

Yes, same comment as above. We want to turn off PHYs which don't have
a driver.

  Andrew