linux-kernel - Re: [PATCH 3/3] arm64: dts: qcom: sm6115: Add USB SS qmp phy node

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Message-ID: <ecb2c9ff-b092-22fa-c91e-01ead6266457@linaro.org>
Date:   Tue, 13 Dec 2022 19:59:53 +0100
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Bhupesh Sharma <bhupesh.sharma@...aro.org>
Cc:     linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
        agross@...nel.org, bhupesh.linux@...il.com,
        linux-kernel@...r.kernel.org, robh+dt@...nel.org,
        konrad.dybcio@...aro.org, andersson@...nel.org
Subject: Re: [PATCH 3/3] arm64: dts: qcom: sm6115: Add USB SS qmp phy node

On 13/12/2022 19:52, Bhupesh Sharma wrote:
> Hi Krzysztof,
> 
> On Tue, 13 Dec 2022 at 18:26, Krzysztof Kozlowski
> <krzysztof.kozlowski@...aro.org> wrote:
>>
>> On 13/12/2022 13:38, Bhupesh Sharma wrote:
>>> Add USB superspeed qmp phy node to dtsi.
>>>
>>> Signed-off-by: Bhupesh Sharma <bhupesh.sharma@...aro.org>
>>> ---
>>>  arch/arm64/boot/dts/qcom/sm6115.dtsi | 38 ++++++++++++++++++++++++++--
>>>  1 file changed, 36 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/arch/arm64/boot/dts/qcom/sm6115.dtsi b/arch/arm64/boot/dts/qcom/sm6115.dtsi
>>> index e4ce135264f3d..9c5c024919f92 100644
>>> --- a/arch/arm64/boot/dts/qcom/sm6115.dtsi
>>> +++ b/arch/arm64/boot/dts/qcom/sm6115.dtsi
>>> @@ -579,6 +579,40 @@ usb_hsphy: phy@...3000 {
>>>                       status = "disabled";
>>>               };
>>>
>>> +             usb_qmpphy: phy@...5000 {
>>> +                     compatible = "qcom,sm6115-qmp-usb3-phy";
>>> +                     reg = <0x01615000 0x200>;
>>> +                     #clock-cells = <1>;
>>> +                     #address-cells = <1>;
>>> +                     #size-cells = <1>;
>>> +                     ranges;
>>> +                     clocks = <&gcc GCC_USB3_PRIM_PHY_COM_AUX_CLK>,
>>> +                              <&gcc GCC_USB3_PRIM_CLKREF_CLK>,
>>> +                              <&gcc GCC_AHB2PHY_USB_CLK>;
>>> +                     clock-names = "com_aux",
>>> +                                   "ref",
>>> +                                   "cfg_ahb";
>>> +                     resets = <&gcc GCC_USB3_PHY_PRIM_SP0_BCR>,
>>> +                              <&gcc GCC_USB3PHY_PHY_PRIM_SP0_BCR>;
>>> +                     reset-names = "phy", "phy_phy";
>>> +                     status = "disabled";
>>
>> Hm, you add a disabled PHY which is used by existing controller. The
>> controller is enabled in board DTS, but new PHY node isn't. Aren't you
>> now breaking it?
> 
> The USB controller is connected to two PHYs - one is HS PHY and the other is SS
> QMP Phy. So while the exiting board dts describes and uses only the HS
> PHY, newer
> board dts files (which will soon be sent out as a separate patch),

Then I miss how do you narrow the existing DTS to use only one PHY. I
don't see anything in this patchset.

> will use both the HS and SS
> USB PHYs.
> 
> So, this will not break the existing board dts files.

I still think it will be. The board boots with USB with one phy enabled
and one disabled. The driver gets phys unconditionally and one of them
is disabled.

Even if Linux implementation will work (devm_usb_get_phy_by_phandle will
return -ENXIO or -ENODEV for disabled node), it is still a bit confusing
and I wonder how other users of such DTS should behave. Although it will
affect only one board, so maybe there are no other users?

Best regards,
Krzysztof