linux-kernel - Re: [PATCH v16 2/2] arm64: dts: qcom: sa8295p: Enable tertiary controller and its 4 USB ports

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Date: Tue, 30 Apr 2024 08:24:54 +0200
From: Johan Hovold <johan@...nel.org>
To: Krishna Kurapati <quic_kriskura@...cinc.com>
Cc: Krzysztof Kozlowski <krzk+dt@...nel.org>, Rob Herring <robh@...nel.org>,
	Bjorn Andersson <andersson@...nel.org>,
	Konrad Dybcio <konrad.dybcio@...aro.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 v16 2/2] arm64: dts: qcom: sa8295p: Enable tertiary
 controller and its 4 USB ports

On Mon, Apr 29, 2024 at 09:50:48PM +0530, Krishna Kurapati wrote:
> Multiport USB controller (host-only) of SA8295 ADP has 4 Type-A ports
> exposed for connecting peripherals. The VBUS to these peripherals is
> provided by TPS2559QWDRCTQ1 regulators connected to these ports. Each
> regulator has an enable pin controlled by PMM8540. Since these regulators
> are GPIO controlled regulators, model them as fixed regulators and keep
> them Always-On at boot since we are wakeup capable and we don't need to
> turn them off on suspend.

This does not follow from the fact that the controller is wakeup
capable. What matters is if user space has enabled wakeup from suspend
or not.

Perhaps the driver cannot handle vbus regulators currently and that's
why you do things this way, but the commit message here should at least
be updated to reflect that.

> Also since we don't enter device mode, these
> regulators can be kept on.

Not sure this is needed. You already mentioned that the controller is
host-only above.

Johan