linux-kernel - Re: [PATCH v2 1/2] dt-bindings: usb: ti,hd3ss3220: Add support for VBUS based on ID state

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Message-ID: <cbpne2d7yr2vpxmrrveqajlp3irzsglxroxyyjmviuci2ewted@6ewwp6yyybk5>
Date: Thu, 9 Oct 2025 17:38:32 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
To: Rob Herring <robh@...nel.org>
Cc: Krishna Kurapati <krishna.kurapati@....qualcomm.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Liam Girdwood <lgirdwood@...il.com>, Mark Brown <broonie@...nel.org>,
        Biju Das <biju.das.jz@...renesas.com>, linux-usb@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/2] dt-bindings: usb: ti,hd3ss3220: Add support for
 VBUS based on ID state

On Thu, Oct 09, 2025 at 08:15:43AM -0500, Rob Herring wrote:
> On Wed, Oct 08, 2025 at 09:31:59PM +0300, Dmitry Baryshkov wrote:
> > On Wed, Oct 08, 2025 at 11:27:49PM +0530, Krishna Kurapati wrote:
> > > Update the bindings to support reading ID state and VBUS, as per the
> > > HD3SS3220 data sheet. The ID pin is kept high if VBUS is not at VSafe0V and
> > > asserted low once VBUS is at VSafe0V, enforcing the Type-C requirement that
> > > VBUS must be at VSafe0V before re-enabling VBUS.
> > > 
> > > Add id-gpios property to describe the input gpio for USB ID pin and vbus-
> > > supply property to describe the regulator for USB VBUS.
> > > 
> > > Signed-off-by: Krishna Kurapati <krishna.kurapati@....qualcomm.com>
> > > ---
> > >  .../devicetree/bindings/usb/ti,hd3ss3220.yaml       | 13 +++++++++++++
> > >  1 file changed, 13 insertions(+)
> > > 
> > > diff --git a/Documentation/devicetree/bindings/usb/ti,hd3ss3220.yaml b/Documentation/devicetree/bindings/usb/ti,hd3ss3220.yaml
> > > index bec1c8047bc0..c869eece39a7 100644
> > > --- a/Documentation/devicetree/bindings/usb/ti,hd3ss3220.yaml
> > > +++ b/Documentation/devicetree/bindings/usb/ti,hd3ss3220.yaml
> > > @@ -25,6 +25,19 @@ properties:
> > >    interrupts:
> > >      maxItems: 1
> > >  
> > > +  id-gpios:
> > > +    description:
> > > +      An input gpio for USB ID pin. Upon detecting a UFP device, HD3SS3220
> > > +      will keep ID pin high if VBUS is not at VSafe0V. Once VBUS is at VSafe0V,
> > > +      the HD3SS3220 will assert ID pin low. This is done to enforce Type-C
> > > +      requirement that VBUS must be at VSafe0V before re-enabling VBUS.
> > > +
> > 
> > Stray empty line?
> > 
> > > +    maxItems: 1
> > > +
> > > +  vbus-supply:
> > > +    description: A phandle to the regulator for USB VBUS if needed when host
> > > +      mode or dual role mode is supported.
> > 
> > Why are we adding the property here while we can use the vbus-supply of
> > the usb-c-connector?
> 
> Normally, that's my question on both of these, too. However, it does 
> look like both are connected to the chip. There's VBUS_DET which is 
> connected to Vbus (thru a 900k resistor). So having these here does look 
> like accurate representation of the h/w. The commit message should make 
> this more clear. Honestly, that's really the only part I care about. 
> How it works is not so important. 

The VBUS_DET pin is used by the controller to detect the VBUS provided
by the USB-C partner and to identify when it's safe to turn on the
device's VBUS supply. I think this still fits into the description of
the connector's vbus-supply.

-- 
With best wishes
Dmitry