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SubjectRe: [PATCH v1 2/4] dt-bindings: clock: Add support for the MSM8998 mmcc
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On 2/5/2019 3:16 PM, Stephen Boyd wrote:
> Quoting Jeffrey Hugo (2019-02-05 14:08:43)
>> On 2/5/2019 3:02 PM, Stephen Boyd wrote:
>>> Quoting Jeffrey Hugo (2019-01-30 08:35:59)
>>>> Document the multimedia clock controller found on MSM8998
>>>>
>>>> Signed-off-by: Jeffrey Hugo <jhugo@codeaurora.org>
>>>> ---
>>>> Documentation/devicetree/bindings/clock/qcom,mmcc.txt | 7 +++++++
>>>> 1 file changed, 7 insertions(+)
>>>>
>>>> diff --git a/Documentation/devicetree/bindings/clock/qcom,mmcc.txt b/Documentation/devicetree/bindings/clock/qcom,mmcc.txt
>>>> index 8b0f784..ae85bca 100644
>>>> --- a/Documentation/devicetree/bindings/clock/qcom,mmcc.txt
>>>> +++ b/Documentation/devicetree/bindings/clock/qcom,mmcc.txt
>>>> @@ -10,11 +10,18 @@ Required properties :
>>>> "qcom,mmcc-msm8960"
>>>> "qcom,mmcc-msm8974"
>>>> "qcom,mmcc-msm8996"
>>>> + "qcom,mmcc-msm8998"
>>>>
>>>> - reg : shall contain base register location and length
>>>> - #clock-cells : shall contain 1
>>>> - #reset-cells : shall contain 1
>>>>
>>>> +For MSM8998 only:
>>>> + - clocks: a list of phandles and clock-specifier pairs,
>>>> + one for each entry in clock-names.
>>>> + - clock-names: "xo" for the xo clock,
>>>> + "gpll0" for the global pll 0 clock.
>>>
>>> Wouldn't the DSI plls also be listed here? And anything else that is
>>> external to this clock controller?
>>>
>>
>> We can't get the DSI plls from DT as far as I am aware (upstream). That
>> is why I mentioned in the cover letter we need to rely on the global
>> namespace.
>
> Why not? Because the DSI PLL isn't a clk provider? Or it doesn't have
> #clock-cells? Please try to use the DSI PLLs from DT or at least specify
> them in the binding as optional clocks that may not matter if DSI is not
> enabled for example.

I had thought that there wasn't a DT node that exposed those (I find it
very odd how the DSI PLLs get inited), but upon checking again, I see
what I have missed. I'll need to incorporate them now.

>
>>
>> Also, the DSI plls, etc present a chicken and egg situation, as the plls
>> require mmcc, and mmcc requires the plls. I forsee an unsolvable
>> EPROBE_DEFER issue.
>>
>
> We've "solved" that problem with orphan clks and the clk parent rewrite
> series. Maybe you can try it out to help flush out any bugs lurking
> there.
>

Thanks for the reference in your other reply. Will have a look.

--
Jeffrey Hugo
Qualcomm Datacenter Technologies as an affiliate of Qualcomm
Technologies, Inc.
Qualcomm Technologies, Inc. is a member of the
Code Aurora Forum, a Linux Foundation Collaborative Project.

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