linux-kernel - Re: [PATCH 2/3] arm64: dts: qcom: sc8280xp: Correct USB PHY power domains

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Date: Fri, 29 Dec 2023 14:06:26 +0100
From: Konrad Dybcio <konrad.dybcio@...aro.org>
To: Johan Hovold <johan@...nel.org>
Cc: Bjorn Andersson <andersson@...nel.org>, Rob Herring <robh+dt@...nel.org>,
 Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
 Conor Dooley <conor+dt@...nel.org>, Johan Hovold <johan+linaro@...nel.org>,
 Marijn Suijten <marijn.suijten@...ainline.org>,
 linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org,
 Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
 Konrad Dybcio <konrad.dybcio@...ainline.org>
Subject: Re: [PATCH 2/3] arm64: dts: qcom: sc8280xp: Correct USB PHY power
 domains

On 29.12.2023 14:01, Johan Hovold wrote:
> On Wed, Dec 27, 2023 at 11:28:27PM +0100, Konrad Dybcio wrote:
>> The USB GDSCs are only related to the controllers.
> 
> Are you sure?
That's what I've been told from rather reliable sources.

> 
>> The PHYs on the other
>> hand, are powered by VDD_MX and their specific VDDA_PHY/PLL regulators.
>>
>> Fix the power-domains assignment to stop potentially toggling the GDSC
>> unnecessarily.
> 
> Again, there's no additional toggling being done here, but yes, this may
> keep the domains enabled during suspend depending on how the driver is
> implemented.
No, it can actually happen. (Some) QMP PHYs are referenced by the
DP hardware. If USB is disabled (or suspended), the DP being active
will hold these GDSCs enabled.

Konrad
> If that's the concern, then please spell that out too.
> 
>> Fixes: 152d1faf1e2f ("arm64: dts: qcom: add SC8280XP platform")
> 
> May not be needed either.
> 
>> @@ -2597,7 +2597,7 @@ usb_2_qmpphy0: phy@...f000 {
>>  				 <&gcc GCC_USB3UNIPHY_PHY_MP0_BCR>;
>>  			reset-names = "phy", "phy_phy";
>>  
>> -			power-domains = <&gcc USB30_MP_GDSC>;
>> +			power-domains = <&rpmhpd SC8280XP_MX>;
> 
> Johan