Messages in this thread | | | From | Grant Likely <> | Date | Tue, 13 Dec 2011 11:03:57 -0700 | Subject | Re: [RFC v2 4/9] of: add clock providers |
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On Tue, Dec 13, 2011 at 11:01 AM, Rob Herring <robherring2@gmail.com> wrote: > Grant, > > On 12/13/2011 11:54 AM, Grant Likely wrote: >> On Mon, Dec 12, 2011 at 4:29 PM, Jamie Iles <jamie@jamieiles.com> wrote: >>> Hi Grant, >>> >>> I'm still going through these and trying to digest them but a couple of >>> quick questions/comments. >>> >>> Jamie >>> >>> On Mon, Dec 12, 2011 at 03:02:04PM -0700, Grant Likely wrote: >>>> diff --git a/Documentation/devicetree/bindings/clock/clock-bindings.txt b/Documentation/devicetree/bindings/clock/clock-bindings.txt >>>> new file mode 100644 >>>> index 0000000..e40c436 >>>> --- /dev/null >>>> +++ b/Documentation/devicetree/bindings/clock/clock-bindings.txt >>>> @@ -0,0 +1,114 @@ >>>> +This binding is a work-in-progress, and are based on some experimental >>>> +work by benh[1]. >>>> + >>>> +Sources of clock signal can be represented by any node in the device >>>> +tree. Those nodes are designated as clock providers. Clock consumer >>>> +nodes use a phandle and clock specifier pair to connect clock provider >>>> +outputs to clock inputs. Similar to the gpio specifiers, a clock >>>> +specifier is an array of one more more cells identifying the clock >>>> +output on a device. The length of a clock specifier is defined by the >>>> +value of a #clock-cells property in the clock provider node. >>>> + >>>> +[1] http://patchwork.ozlabs.org/patch/31551/ >>>> + >>>> +==Clock providers== >>>> + >>>> +Required properties: >>>> +#clock-cells: Number of cells in a clock specifier; typically will be >>>> + set to 1 >>> >>> I'm not sure I fully understand what the extra cells actually mean for >>> clocks. I think the first integer is the clock output to use but some >>> of the versatile and highbank ones only have a phandle or is it more >>> implementation defined? The clock-output-names description hints at >>> recommended, so I find this a little confusing, but that could just be >>> me! >> >> I'm following convention here that has been established with >> interrupts, gpios, and others. Sometimes more information is needed >> that just the clock number. Using #clock-cells gives a clock provider >> the option of having additional fields for clock flags or other data. >> This is very much implementation defined. Simple clock providers that >> only have a single clock output can easily use #clock-cells = <0>. >> Providers with multiple outputs will need to use 1 or more cells. >> > > Aren't you off by 1 here? The minimum cells is 1 to hold the phandle of > the source/parent. Multiple outputs will need a cell size of 2 (typically).
No. The #clock-cells does not include the phandle. Never did.
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