On Mon, Oct 17, 2011 at 06:53:03PM +0800, Richard Zhao wrote:

On Mon, Oct 17, 2011 at 10:20:28AM +0100, Mark Brown wrote:

quoted

On Mon, Oct 17, 2011 at 04:48:52PM +0800, Richard Zhao wrote:

quoted

For example, devices that possible access to on-chip RAM, depend on OCRAM clock. 
On imx53, VPU depends on OCRAM clock, even when VPU does not use OCRAM.

So if the VPU depends on OCRAM the VPU should be enabling the OCRAM
clock.  The function of a given clock isn't terribly relevant, and
certainly grouping clocks together doesn't seem to be the obvious
solution from what you've said

VPU don't know OCRAM clk, it's SoC specific. I know it's clock function
replationship. But it's the only better place to refect the dependency 
in clock tree. Another dependency example, from SoC bus topology, some bus
clk always depends on bus switch/hub.

quoted

- if the driver doesn't know about the
clock it seems like the core ought to be enabling it transparently
rather than gluing it together with some other random clock.

If you mean clk core here, then we need things like below:
struct clk_hw {
	struct clk *clk;
	struct dependency {
		struct clk_hw *clks;
		int count;
	};
};
Though Mike does not like to add things in clk_hw, but it's the only place
to put common things of clk drivers.

It's not a problem to associate multiple clocks to a device, we can do
this now already. What a driver can't do now is give-me-all-clocks-I-need(dev),
but this problem should not be solved at clock core level but at the
clkdev level.
The fact is that the different clocks for a device are really different
clocks. A dumb driver may want to request/enable all relevant clocks at
once while a more sophisticated driver may want to enable the clock for
accessing registers in the probe function and a baud clock on device
open time.

Sascha

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