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

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Message-ID: <20220915022025.rwqooixqhhuott6n@builder.lan>
Date:   Wed, 14 Sep 2022 21:20:25 -0500
From:   Bjorn Andersson <andersson@...nel.org>
To:     Rajendra Nayak <quic_rjendra@...cinc.com>
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 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?

Also, how about adding the same to &usb_2, while we're at it?

Regards,
Bjorn

>  
>  			resets = <&gcc GCC_USB30_PRIM_BCR>;
>  
> -- 
> 2.17.1
>