Re: [PATCH 1/3] Documentation: dt: Add TI SCI clock driver

[Rob Herring <robh@kernel.org>]

On Mon, Oct 31, 2016 at 7:50 AM, Tero Kristo <t-kristo@ti.com> wrote:
> On 30/10/16 22:41, Rob Herring wrote:
>>
>> On Fri, Oct 21, 2016 at 03:45:59PM +0300, Tero Kristo wrote:
>>>
>>> Add a clock implementation, TI SCI clock, that will hook to the common
>>> clock framework, and allow each clock to be controlled via TI SCI
>>> protocol.
>>>
>>> Signed-off-by: Tero Kristo <t-kristo@ti.com>
>>> ---
>>>  .../devicetree/bindings/clock/ti,sci-clk.txt       | 37
>>> ++++++++++++++++++++++
>>>  MAINTAINERS                                        |  1 +
>>>  2 files changed, 38 insertions(+)
>>>  create mode 100644
>>> Documentation/devicetree/bindings/clock/ti,sci-clk.txt
>>>
>>> diff --git a/Documentation/devicetree/bindings/clock/ti,sci-clk.txt
>>> b/Documentation/devicetree/bindings/clock/ti,sci-clk.txt
>>> new file mode 100644
>>> index 0000000..bfc3ca4
>>> --- /dev/null
>>> +++ b/Documentation/devicetree/bindings/clock/ti,sci-clk.txt
>>> @@ -0,0 +1,37 @@
>>> +Texas Instruments TI-SCI Clocks
>>> +===============================
>>> +
>>> +All clocks on Texas Instruments' SoCs that contain a System Controller,
>>> +are only controlled by this entity. Communication between a host
>>> processor
>>> +running an OS and the System Controller happens through a protocol known
>>> +as TI-SCI[1]. This clock implementation plugs into the common clock
>>> +framework and makes use of the TI-SCI protocol on clock API requests.
>>> +
>>> +[1] Documentation/devicetree/bindings/arm/keystone/ti,sci.txt
>>> +
>>> +Required properties:
>>> +-------------------
>>> +- compatible: Must be "ti,k2g-sci-clk"
>>> +- #clock-cells: Shall be 2.
>>> +  In clock consumers, this cell represents the device ID and clock ID
>>> +  exposed by the PM firmware. The assignments can be found in the header
>>> +  files <dt-bindings/genpd/<soc>.h> (which covers the device IDs) and
>>> +  <dt-bindings/clock/<soc>.h> (which covers the clock IDs), where <soc>
>>> +  is the SoC involved, for example 'k2g'.
>>> +
>>> +Examples:
>>> +--------
>>> +
>>> +pmmc: pmmc {
>>> +       compatible = "ti,k2g-sci";
>>> +
>>> +       k2g_clks: k2g_clks {
>>
>>
>> Use "clocks" for node name instead.
>>
>>> +               compatible = "ti,k2g-sci-clk";
>>
>>
>> I'm starting to think all these child nodes for SCI are pointless. Is
>> there any reason why the parent node can't be the clock provider (along
>> with all the other providers it acks as)?
>
>
> I believe the only reason to keep them separate is to have kernel side of
> things modular. If we have separate nodes, the drivers can be probed
> separately.
>
> If not, we need to build one huge blob with all the features in it, so the
> main driver can probe everything in one go, with annoying back-and-forth
> callbacks in place (assuming we still want to keep stuff somehow modular.)

Since when is DT the only way to create a device? The main driver can
create devices for all the sub-functions like clocks. This is the same
as MFDs which have been done both ways.

Rob