linux-kernel - Re: [PATCH] arm64: dts: qcom: sc7280: Add required-opps for USB

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Message-ID: <49b835f4-cea8-6422-fa53-7c0ef443873b@quicinc.com>
Date:   Thu, 15 Sep 2022 13:05:32 +0530
From:   Rajendra Nayak <quic_rjendra@...cinc.com>
To:     Bjorn Andersson <andersson@...nel.org>
CC:     <agross@...nel.org>, <konrad.dybcio@...ainline.org>,
        <robh+dt@...nel.org>, <krzysztof.kozlowski+dt@...aro.org>,
        <linux-arm-msm@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <sboyd@...nel.org>,
        <mka@...omium.org>, <johan+linaro@...nel.org>,
        <quic_kriskura@...cinc.com>, <dianders@...omium.org>
Subject: Re: [PATCH] arm64: dts: qcom: sc7280: Add required-opps for USB


On 9/15/2022 7:50 AM, Bjorn Andersson wrote:
> On Wed, Sep 14, 2022 at 11:00:17AM +0530, Rajendra Nayak wrote:
>> USB has a requirement to put a performance state vote on 'cx'
>> while active. Use 'required-opps' to pass this information from
>> device tree, and since all the GDSCs in GCC (including USB) are
>> sub-domains of cx, we also add cx as a power-domain for GCC.
>> Now when any of the consumers of the GDSCs (in this case USB)
>> votes on a perforamance state, genpd framework can identify that
>> the GDSC itself does not support a performance state and it
>> then propogates the vote to the parent, which in this case is cx.
>>
>> This change would also mean that any GDSC in GCC thats left enabled
>> during low power state (perhaps because its marked with a
>> ALWAYS_ON flag) can prevent the system from entering low power
>> since that would prevent cx from transitioning to low power.
>> Ideally any consumers that would need to have their devices
>> (partially) powered to support wakeups should look at making the
>> resp. GDSCs transtion to a Retention (PWRSTS_RET) state instead
>> of leaving them ALWAYS_ON.
>>
>> Signed-off-by: Rajendra Nayak <quic_rjendra@...cinc.com>
>> ---
>> * This patch is a follow up based on the discussion on the previously
>>    posted version to support USB performance state voting [1]
>>
>> * Another patch that this approach depends on is the one to fix the
>>    handling of PWRSTS_RET in the GDSC driver [2] so we can have USB
>>    GDSC transtion to a RET state instead of marking it ALWAYS_ON
>>
>> [1] https://lore.kernel.org/linux-usb/YTduDqCO9aUyAsw1@ripper/
>> [2] https://lore.kernel.org/all/20220901101756.28164-1-quic_rjendra@quicinc.com/#t
>>
>>   arch/arm64/boot/dts/qcom/sc7280.dtsi | 2 ++
>>   1 file changed, 2 insertions(+)
>>
>> diff --git a/arch/arm64/boot/dts/qcom/sc7280.dtsi b/arch/arm64/boot/dts/qcom/sc7280.dtsi
>> index ad04025a8a1a..8a21446738bf 100644
>> --- a/arch/arm64/boot/dts/qcom/sc7280.dtsi
>> +++ b/arch/arm64/boot/dts/qcom/sc7280.dtsi
>> @@ -828,6 +828,7 @@
>>   			#clock-cells = <1>;
>>   			#reset-cells = <1>;
>>   			#power-domain-cells = <1>;
>> +			power-domains = <&rpmhpd SC7280_CX>;
>>   		};
>>   
>>   		ipcc: mailbox@...000 {
>> @@ -3456,6 +3457,7 @@
>>   					  "ss_phy_irq";
>>   
>>   			power-domains = <&gcc GCC_USB30_PRIM_GDSC>;
>> +			required-opps = <&rpmhpd_opp_svs>;
> 
> The patch looks really good, but don't you need &rpmhpd_opp_nom for the
> 200MHz assigned to GCC_USB30_PRIM_MASTER_CLK?

you are right, I wrote this patch a long while back, not sure if
we were on a lower clock back then, thanks for catching, I will fix it
and repost.
  
> Also, how about adding the same to &usb_2, while we're at it?

Sure, will do that as well. thanks.

> 
> Regards,
> Bjorn
> 
>>   
>>   			resets = <&gcc GCC_USB30_PRIM_BCR>;
>>   
>> -- 
>> 2.17.1
>>