linux-kernel - Re: [PATCH 2/3] dt-bindings: clock: qcom,gcc-sc7180: document CX power domain

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Message-ID: <40854a28-3f64-c0fd-9b77-db92cb0fbe13@quicinc.com>
Date:   Wed, 12 Apr 2023 11:12:50 +0530
From:   Rajendra Nayak <quic_rjendra@...cinc.com>
To:     Konrad Dybcio <konrad.dybcio@...aro.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Taniya Das <tdas@...eaurora.org>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        <linux-arm-msm@...r.kernel.org>, <linux-clk@...r.kernel.org>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/3] dt-bindings: clock: qcom,gcc-sc7180: document CX
 power domain


On 4/11/2023 7:15 PM, Konrad Dybcio wrote:
> 
> 
> On 11.04.2023 15:31, Rajendra Nayak wrote:
>>
>> On 4/11/2023 4:57 PM, Konrad Dybcio wrote:
>>>
>>>
>>> On 11.04.2023 06:56, Rajendra Nayak wrote:
>>>>
>>>>
>>>> On 4/8/2023 7:33 PM, Konrad Dybcio wrote:
>>>>>
>>>>>
>>>>> On 8.04.2023 15:48, Krzysztof Kozlowski wrote:
>>>>>> The GCC clock controller needs CX power domain, at least according to
>>>>>> DTS:
>>>>>>
>>>>>>      sc7180-trogdor-pompom-r3.dtb: clock-controller@...000: Unevaluated properties are not allowed ('power-domains' was unexpected)
>>>>>>
>>>>>> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
>>>>>> ---
>>>>> +CC Rajendra (author of 5d6fc6321db1 ("arm64: dts: qcom:
>>>>> sc7180: Add required-opps for USB"))
>>>>>
>>>>> Rajendra, shouldn't SC7180 GCC have PM ops to make sure a vote
>>>>> is only there when AP is active?
>>> So IIUC, CX is never supposed to be shut down?
>>
>> Atleast sc7180 and sc7280 do not support full CX shutdown (or power
>> collapse as its called), it only transitions to a Retention state
>> and even that in the system-wide suspend path only
> And won't outstanding votes on that resource prevent the system
> from entering a system-wide low power state?

I think most of what you are asking was discussed at 
https://lore.kernel.org/all/5ff21b1e-3af9-36ef-e13e-fa33f526d0e3@quicinc.com/

Are we seeing something broken on sc7180/sc7280 platforms?
If there is an outstanding vote on CX it would prevent CX from
going down, but ideally we should not have an outstanding vote
from USB (atleast) since we now support RET for the USB GDSC.
If there is some other GDSC (within GCC) thats left turned ON,
yes, that would still prevent CX from going down.

> 
> Konrad
>>
>>>
>>> Konrad
>>>>
>>>> hmm, I am not quite sure why we would want the performance votes
>>>> from peripherals dropped when CPUs go down in idle?
>>>>
>>>>> Are all GDSCs powered by CX?
>>>>> If not, wouldn't this also need power-domain-names to
>>>>> facilitate e.g. potential MX-powered ones?
>>>>
>>>> For sc7180 GCC, yes.
>>>>
>>>>>
>>>>> Konrad
>>>>>>     .../devicetree/bindings/clock/qcom,gcc-sc7180.yaml         | 7 +++++++
>>>>>>     1 file changed, 7 insertions(+)
>>>>>>
>>>>>> diff --git a/Documentation/devicetree/bindings/clock/qcom,gcc-sc7180.yaml b/Documentation/devicetree/bindings/clock/qcom,gcc-sc7180.yaml
>>>>>> index 06dce0c6b7d0..8bf9b6f49550 100644
>>>>>> --- a/Documentation/devicetree/bindings/clock/qcom,gcc-sc7180.yaml
>>>>>> +++ b/Documentation/devicetree/bindings/clock/qcom,gcc-sc7180.yaml
>>>>>> @@ -32,6 +32,10 @@ properties:
>>>>>>           - const: bi_tcxo_ao
>>>>>>           - const: sleep_clk
>>>>>>     +  power-domains:
>>>>>> +    items:
>>>>>> +      - description: CX domain
>>>>>> +
>>>>>>     required:
>>>>>>       - compatible
>>>>>>       - clocks
>>>>>> @@ -45,6 +49,8 @@ unevaluatedProperties: false
>>>>>>     examples:
>>>>>>       - |
>>>>>>         #include <dt-bindings/clock/qcom,rpmh.h>
>>>>>> +    #include <dt-bindings/power/qcom-rpmpd.h>
>>>>>> +
>>>>>>         clock-controller@...000 {
>>>>>>           compatible = "qcom,gcc-sc7180";
>>>>>>           reg = <0x00100000 0x1f0000>;
>>>>>> @@ -52,6 +58,7 @@ examples:
>>>>>>                    <&rpmhcc RPMH_CXO_CLK_A>,
>>>>>>                    <&sleep_clk>;
>>>>>>           clock-names = "bi_tcxo", "bi_tcxo_ao", "sleep_clk";
>>>>>> +      power-domains = <&rpmhpd SC7180_CX>;
>>>>>>           #clock-cells = <1>;
>>>>>>           #reset-cells = <1>;
>>>>>>           #power-domain-cells = <1>;