linux-kernel - Re: [PATCH v11 13/13] arm64: dts: qcom: sa8540-ride: Enable first port of tertiary usb controller

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Date:   Mon, 2 Oct 2023 11:47:52 +0200
From:   Konrad Dybcio <konrad.dybcio@...aro.org>
To:     Krishna Kurapati PSSNV <quic_kriskura@...cinc.com>,
        Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Felipe Balbi <balbi@...nel.org>,
        Wesley Cheng <quic_wcheng@...cinc.com>,
        Johan Hovold <johan@...nel.org>,
        Mathias Nyman <mathias.nyman@...el.com>
Cc:     linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
        quic_pkondeti@...cinc.com, quic_ppratap@...cinc.com,
        quic_jackp@...cinc.com, ahalaney@...hat.com,
        quic_shazhuss@...cinc.com
Subject: Re: [PATCH v11 13/13] arm64: dts: qcom: sa8540-ride: Enable first
 port of tertiary usb controller



On 9/14/23 17:45, Krishna Kurapati PSSNV wrote:
> 
> 
> On 9/13/2023 5:40 PM, Konrad Dybcio wrote:
>> On 7.09.2023 05:36, Krishna Kurapati PSSNV wrote:
>>>
>>>
>>>> Is there any benefit to removing the other ports?
>>>>
>>>> i.e. are ports 1-3 not parked properly by the dwc3 driver if
>>>> they're never connected to anything?
>>>>
>>> Hi Konrad,
>>>
>>>   Whether or not the phy is connected to a port, the controller would 
>>> modify the GUSB2PHYCFG/GUSB3PIPECTL registers. But if we don't 
>>> specify only one phy and let phys from base DTSI take effect (4 HS / 
>>> 2 SS), we would end up initializing and powering on phy's which are 
>>> never connected to a port. To avoid that we need to specify only one 
>>> phy for this platform.
>> And does that have any major effect on power use?
>>
>> Do these PHYs not have some dormant/low power mode?
>>
> Hi Konrad,
> 
>   I believe there will be some minimal power use. IMO its best to keep 
> only one phy enabled for this variant instead of giving all and 
> initializing/powering-on all 4 of them.
Okay let's not waste power..

Konrad