Re: [PATCH v2] usb: dwc3: Add support for VBUS power control

[Mike Looijmans]

Met vriendelijke groet / kind regards,

Mike Looijmans
System Expert


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On 17-06-2020 18:13, Rob Herring wrote:
> On Wed, Jun 17, 2020 at 8:38 AM Mike Looijmans <mike.looijmans@xxxxxxxx> wrote:
> > Met vriendelijke groet / kind regards,
> >
> > Mike Looijmans
> > System Expert
> >
> >
> > TOPIC Embedded Products B.V.
> > Materiaalweg 4, 5681 RJ Best
> > The Netherlands
> >
> > T: +31 (0) 499 33 69 69
> > E: mike.looijmans@xxxxxxxxxxxxxxxxx
> > W: www.topicproducts.com
> >
> > Please consider the environment before printing this e-mail
> > On 10-06-2020 22:22, Rob Herring wrote:
> > > On Wed, Jun 03, 2020 at 02:09:15PM +0200, Mike Looijmans wrote:
> > > > Support VBUS power control using regulator framework. Enables the regulator
> > > > while the port is in host mode.
> > > >
> > > > Signed-off-by: Mike Looijmans <mike.looijmans@xxxxxxxx>
> > > > ---
> > > > v2: Add missing devm_regulator_get call which got lost during rebase
> > > >
> > > >    .../devicetree/bindings/usb/dwc3.txt          |  1 +
> > > >    drivers/usb/dwc3/core.c                       | 34 ++++++++++++++-----
> > > >    drivers/usb/dwc3/core.h                       |  4 +++
> > > >    drivers/usb/dwc3/drd.c                        |  6 ++--
> > > >    4 files changed, 33 insertions(+), 12 deletions(-)
> > > >
> > > > diff --git a/Documentation/devicetree/bindings/usb/dwc3.txt b/Documentation/devicetree/bindings/usb/dwc3.txt
> > > > index 9946ff9ba735..56bc3f238e2d 100644
> > > > --- a/Documentation/devicetree/bindings/usb/dwc3.txt
> > > > +++ b/Documentation/devicetree/bindings/usb/dwc3.txt
> > > > @@ -37,6 +37,7 @@ Optional properties:
> > > >     - phys: from the *Generic PHY* bindings
> > > >     - phy-names: from the *Generic PHY* bindings; supported names are "usb2-phy"
> > > >       or "usb3-phy".
> > > > + - vbus-supply: Regulator handle that provides the VBUS power.
> > > Does the DWC3 block require Vbus to power itself? Doubtful. This
> > > belongs in a usb-connector node. If the DWC3 driver wants to get the
> > > Vbus supply, it can fetch it from that node.
> > >
> > > Rob
> > Okay, I've been digging into that. But there's no actual driver that
> > binds to a "usb-b-connector" compatible, so how do we get to the
> > vbus-supply from there?
> >
> > [devm_]regulator_get only accepts a device as argument, and will not
> > look into child nodes. The only way to get at the vbus of a child node
> > (or a node linked through a port) would be to hand-code the equivalent
> > of of_regulator_get(), which will not be acceptable.
> Doesn't it look into child nodes calling of_get_child_regulator()?
Looking at the code in regulator/core.c, yeah, it should. I'll have to 
add some debugging lines and look into why it didn't work in my test.
> You're right that it wouldn't work if graph is used. The connector has
> to be either a child of a controller for the connector or the USB
> controller. I'd expect you'd have the former for Type-C, but for
> "usb-b-connector" the parent is more likely just the USB controller.
For my current case, using a direct child would be fine, there's nothing 
else connected. But I expect that we'll produce a board with some USB-C 
connector some day yeah.
> In any case, having a struct device shouldn't be a requirement and
> most subsystems expose a get function only needing the DT node.
>
> > Or is it the intention that I write a usb-X-connector device driver
> > first that handles the vbus?
> That's a kernel implementation detail that is independent of the
> binding, but yes we'll probably need a driver or library helper
> functions eventually. Note that it is possible to have a struct device
> without a driver.
>
> Rob


--
Mike Looijmans