On Fri, Jul 3, 2015 at 7:40 AM, Stephen Boyd [off-list ref] wrote:

On 07/01/2015 09:26 PM, Daniel Kurtz wrote:

quoted

On Thu, Jul 2, 2015 at 10:52 AM, James Liao [off-list ref] wrote:

quoted

Hi Daniel,

quoted

quoted

+Required Properties:
+
+- compatible: Should be:
+       - "mediatek,mt8173-imgsys", "syscon"
+- #clock-cells: Must be 1
+
+The imgsys controller uses the common clk binding from
+Documentation/devicetree/bindings/clock/clock-bindings.txt
+The available clocks are defined in dt-bindings/clock/mt*-clk.h.
+
+Example:
+
+imgsys: imgsys at 15000000 {

Since these nodes will be supplying clocks to the rest of the system,
I think the "name" part of each of these should all be
"clock-controller", like topckgen and apmixedsys:

  imgsys: clock-controller at 15000000 {

These subsystems (and topckgen also) also contains other functions such
as reset controller, which may be implemented in clk/mediatek/ in the
future. It is suitable to use "clock-controller" as their name?

Hmm,

I don't know the "right way" to do this either.
Pardon me if you've already had these discussions.
I only recently started looking at these clock nodes in detail :-).

I think what we really have in register space is a "syscon", as
described in [0]:
[0] Documentation/devicetree/bindings/mfd/syscon.txt

So, we can define this block of registers as a syscon:

mmsys_syscon: syscon at 14000000 {
       compatible = "mediatek,mt8173-mmsys", "syscon";
       reg = <0 0x14000000 0 0x1000>;
};


Then for the clock controller functionality, we create a node with a
"clock-controller" name and a "-clock" compatible, like this:

mmsys_clock: clock-controller {
       compatible = "mediatek,mt8173-mmsys-clock";
       #clock-cells = <1>;
       mediatek,syscon = <&mmsys_syscon>;
};

You could then do:
CLK_OF_DECLARE(mtk_mmsys, "mediatek,mt8173-mmsys-clock", mtk_mmsys_init);


If you want to reuse the same register range for some other
functionality, we could then use a different node, with a different
compatible:

mmsys: reset-controller {
       compatible = "mediatek,mt8173-mmsys-reset";
       mediatek,syscon = <&mmsys_syscon>;
};

What do you think of this approach?

DT nodes typically have a reg property. Not having a reg property is a
good indicator of a problem with the binding. A syscon is used when you
have a DT node with a reg property and some driver attached to it, but
you need to poke some bits in another register region that isn't part of
the reg property. Instead of having multiple nodes with two reg
properties where the second one is the same, we use a phandle and a syscon.

If clock-controller isn't acceptable maybe clock-reset-contoller would
work? Or "power-controller"? We certainly shouldn't be making up
multiple nodes for one hardware block. Of course, the subject of the
patch is "bindings for clock controllers", so it may be that the
registers are predominantly clock related and so the name is appropriate
already.

Using "clock-controller" seems to fit best with the bindings
introduced by this patch.

However, if these bindings are for hardware blocks that contain a grab
bag of various functionality that will be added in later patches, then
I think "syscon" might be best.

-Dan

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