linux-kernel - Re: [PATCH] arm64: dts: qcom: sc8280xp: Flush RSC sleep & wake votes

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Date:   Wed, 17 May 2023 23:23:26 +0200
From:   Konrad Dybcio <konrad.dybcio@...aro.org>
To:     Bjorn Andersson <quic_bjorande@...cinc.com>
Cc:     Bjorn Andersson <andersson@...nel.org>,
        Andy Gross <agross@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] arm64: dts: qcom: sc8280xp: Flush RSC sleep & wake votes



On 16.05.2023 23:01, Bjorn Andersson wrote:
> On Mon, May 15, 2023 at 11:34:45AM +0200, Konrad Dybcio wrote:
>>
>>
>> On 15.05.2023 04:38, Bjorn Andersson wrote:
>>> On Sat, May 13, 2023 at 11:09:07AM +0200, Konrad Dybcio wrote:
>>>>
>>>>
>>>> On 12.05.2023 17:04, Bjorn Andersson wrote:
>>>>> The rpmh driver will cache sleep and wake votes until the cluster
>>>>> power-domain is about to enter idle, to avoid unnecessary writes. So
>>>>> associate the apps_rsc with the cluster pd, so that it can be notified
>>>>> about this event.
>>>>>
>>>>> Without this, only AMC votes are being commited.
>>>> Ouch.
>>>>
>>>> Should we make this required: in bindings and add it to all
>>>> platforms?
>>>>
>>>
>>> I though this was an optimization and in the absence of this callback
>>> the driver would just write out wake and sleep sets as well. But per the
>>> current implementation (and perhaps some underlying cause?) it is indeed
>>> required, if you care about power consumption.
>> Hm.. since it's not strictly required for operation, would something
>> like this be fitting?:
>>
> 
> I don't think it's required for operation, but the current
> implementation does require it.
> 
> So I think we should either require it in the binding to mimic the
> implementation, or the implementation should handle either case (only
> with a performance impact)
Let's just require it then.

Konrad
> 
>> oneOf:
>>   - required:
>>       [...]
>>       - power-domains
>>
>>   - required:
>>       [...]
>>     deprecated: true
>>
>> (if it even works this way)
> 
> I don't think it's worth supporting the combinations.
> 
> Regards,
> Bjorn
> 
>>
>> Konrad
>>>
>>>>>
>>>>> Signed-off-by: Bjorn Andersson <quic_bjorande@...cinc.com>
>>>>> ---
>>>> Reviewed-by: Konrad Dybcio <konrad.dybcio@...aro.org>
>>>> Fixes: 152d1faf1e2f ("arm64: dts: qcom: add SC8280XP platform")
>>>>
>>>
>>> The Fixes sounds reasonable.
>>>
>>> Thanks,
>>> Bjorn
>>>
>>>> Konrad
>>>>>  arch/arm64/boot/dts/qcom/sc8280xp.dtsi | 1 +
>>>>>  1 file changed, 1 insertion(+)
>>>>>
>>>>> diff --git a/arch/arm64/boot/dts/qcom/sc8280xp.dtsi b/arch/arm64/boot/dts/qcom/sc8280xp.dtsi
>>>>> index 8fa9fbfe5d00..5c68f2182c2f 100644
>>>>> --- a/arch/arm64/boot/dts/qcom/sc8280xp.dtsi
>>>>> +++ b/arch/arm64/boot/dts/qcom/sc8280xp.dtsi
>>>>> @@ -3982,6 +3982,7 @@ apps_rsc: rsc@...00000 {
>>>>>  			qcom,tcs-config = <ACTIVE_TCS  2>, <SLEEP_TCS   3>,
>>>>>  					  <WAKE_TCS    3>, <CONTROL_TCS 1>;
>>>>>  			label = "apps_rsc";
>>>>> +			power-domains = <&CLUSTER_PD>;
>>>>>  
>>>>>  			apps_bcm_voter: bcm-voter {
>>>>>  				compatible = "qcom,bcm-voter";