Hi Stephen,
On 3 June 2017 at 06:56, Stephen Boyd <sboyd@xxxxxxxxxxxxxx> wrote:
> On 06/01, Chunyan Zhang wrote:
>> The value of property 'clock-cells' is not determined only by the number of
>> clock outputs in one clock node, it is actually determined by whether the
>> clock output in this node can be referenced directly without index. If
>> the output clock has to be referenced by a index, the clock-cell of this
>> clock node can't be defined 0.
>>
>> Signed-off-by: Chunyan Zhang <zhang.chunyan@xxxxxxxxxx>
>> ---
>> Documentation/devicetree/bindings/clock/clock-bindings.txt | 10 ++++++++--
>> 1 file changed, 8 insertions(+), 2 deletions(-)
>
> I'm leaving this patch for Rob/DT maintainers to apply.
>
>>
>> diff --git a/Documentation/devicetree/bindings/clock/clock-bindings.txt b/Documentation/devicetree/bindings/clock/clock-bindings.txt
>> index 2ec489e..cef3db5 100644
>> --- a/Documentation/devicetree/bindings/clock/clock-bindings.txt
>> +++ b/Documentation/devicetree/bindings/clock/clock-bindings.txt
>> @@ -15,8 +15,14 @@ value of a #clock-cells property in the clock provider node.
>>
>> Required properties:
>> #clock-cells: Number of cells in a clock specifier; Typically 0 for nodes
>> - with a single clock output and 1 for nodes with multiple
>> - clock outputs.
>> + with a single clock output and it must be able to be
>> + referenced without index, and 1 for nodes with single or
>> + multiple clock outputs which have to be referenced by index.
>> +
>> + Please note that if a node with a single clock output
>> + but it has "clock-indices" property (see bellow), it has
>> + to be referenced by index, its "#clock-cells" cannot be
>> + defined 0.
>
> Maybe this should be added to the clock-indices area of the
> document instead of here? It seems to me that you can't have
> clock-indices if you have #clock-cells=<0>, and that's sort of
> obvious because 0 cells means 1 output and >0 cells means
> potentially many outputs.
Sorry for not being able to document clear enough.
Let me try to explain why I added this paragraph here rather than
clock-indices area.
The sentence "0 for nodes with a single clock output" made me confused.
In the platform I'm working on, some clock has a single clock output
though, the identifying number for the clock output , #clock-cells
cannot be set 0.
I just wanted to make this sort of cases being cleared. My point was
that clock-cells with zero was not for all kinds of clocks which has
one single output.
I tried to rewrite the description below, would it be better? :)
--- a/Documentation/devicetree/bindings/clock/clock-bindings.txt
+++ b/Documentation/devicetree/bindings/clock/clock-bindings.txt
@@ -18,6 +18,9 @@ Required properties:
with a single clock output and 1 for nodes with multiple
clock outputs.
+ There's one exception, please see the description for
+ clock-indices below.
+
Optional properties:
clock-output-names: Recommended to be a list of strings of clock output signal
names indexed by the first cell in the clock specifier.
@@ -48,6 +51,13 @@ clock-indices: If the identifying number
for the clocks in the node
is not linear from zero, then this allows the mapping of
identifiers into the clock-output-names array.
+ This property not only servers for clocks with multiple
+ clock outputs, but also for clocks with a single clock
+ output whose identifying number is not zero.
+
+ So long as clock-indices is set, clock-cells cannot be
+ set zero.
+
For example, if we have two clocks <&oscillator 1> and <&oscillator 3>:
Thanks for the review,
Chunyan
>
> --
> Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
> a Linux Foundation Collaborative Project
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