linux-kernel - Re: [PATCH 2/3] arm64: dts: qcom: sa8295p: Enable tertiary controller and its 4 USB ports

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Message-ID: <CAA8EJppi+3cJqzkhcaDR_3w_Qhy_AzLBJsW7-dtugzE1egM3Kg@mail.gmail.com>
Date: Thu, 8 Feb 2024 06:41:15 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Krishna Kurapati PSSNV <quic_kriskura@...cinc.com>
Cc: Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>, 
	Konrad Dybcio <konrad.dybcio@...aro.org>, Rob Herring <robh+dt@...nel.org>, 
	Bjorn Andersson <andersson@...nel.org>, Conor Dooley <conor+dt@...nel.org>, linux-kernel@...r.kernel.org, 
	linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org, 
	quic_ppratap@...cinc.com, quic_jackp@...cinc.com
Subject: Re: [PATCH 2/3] arm64: dts: qcom: sa8295p: Enable tertiary controller
 and its 4 USB ports

On Thu, 8 Feb 2024 at 04:40, Krishna Kurapati PSSNV
<quic_kriskura@...cinc.com> wrote:
> On 2/6/2024 6:54 PM, Dmitry Baryshkov wrote:
> > On Tue, 6 Feb 2024 at 14:28, Krishna Kurapati PSSNV
> > <quic_kriskura@...cinc.com> wrote:
> >>
> >>
> >>
> >> On 2/6/2024 5:43 PM, Dmitry Baryshkov wrote:
> >>> On Tue, 6 Feb 2024 at 14:03, Krishna Kurapati <quic_kriskura@...cinc.com> wrote:
> >>>>
> >>>> Enable tertiary controller for SA8295P (based on SC8280XP).
> >>>> Add pinctrl support for usb ports to provide VBUS to connected peripherals.
> >>>
> >>> These are not just pinctrl entries. They hide VBUS regulators. Please
> >>> implement them properly as corresponding vbus regulators.
> >>>
> >>
> >> Hi Dmitry. Apologies, can you elaborate on your comment. I thought this
> >> implementation was fine as Konrad reviewed it in v13 [1]. I removed his
> >> RB tag as I made one change of dropping "_state" in labels.
> >
> > My comment is pretty simple: if I'm not mistaken, your DT doesn't
> > reflect your hardware design.
> > You have actual VBUS regulators driven by these GPIO pins. Is this correct?
> > If so, you should describe them properly in the device tree rather
> > than describing them just as USB host's pinctrl state.
> >
>
> Hi Dmitry,
>
>   I have very little idea about the gpio controller regulators. I will
> go through it and see how I can implement it. I just found this :
> https://www.kernel.org/doc/Documentation/devicetree/bindings/regulator/gpio-regulator.txt

Much simpler, it can be found at
Documentation/devicetree/bindings/regulator/fixed-regulator.yaml

> One query. If we model it as a regulator, do we need to add it as a
> supply and call regulator_enable in dwc3_qcom probe again ?

Not in probe(), but yes. It needs to be enabled when the VBUS has to
be powered up, when the device is initialised or switched to the host
mode, and disabled when the VBUS has to be powered down, if the device
is being switched to the device mode.

-- 
With best wishes
Dmitry