linux-kernel - Re: [PATCH 1/4] dt-bindings: usb: musb: Add support for MediaTek musb controller

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Date:   Fri, 4 Jan 2019 10:10:09 -0600
From:   Rob Herring <robh@...nel.org>
To:     Min Guo <min.guo@...iatek.com>
Cc:     Bin Liu <b-liu@...com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Mark Rutland <mark.rutland@....com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Alan Stern <stern@...land.harvard.edu>,
        Chunfeng Yun <chunfeng.yun@...iatek.com>,
        Linux USB List <linux-usb@...r.kernel.org>,
        devicetree@...r.kernel.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" 
        <linux-arm-kernel@...ts.infradead.org>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-mediatek@...ts.infradead.org>
Subject: Re: [PATCH 1/4] dt-bindings: usb: musb: Add support for MediaTek musb controller

On Thu, Jan 3, 2019 at 9:00 PM Min Guo <min.guo@...iatek.com> wrote:
>
> On Thu, 2019-01-03 at 16:14 -0600, Rob Herring wrote:
> > On Thu, Dec 27, 2018 at 03:34:23PM +0800, min.guo@...iatek.com wrote:
> > > From: Min Guo <min.guo@...iatek.com>
> > >
> > > This adds support for MediaTek musb controller in
> > > host, peripheral and otg mode

[...]

> > > + - interrupts      : interrupt used by musb controller
> > > + - interrupt-names : must be "mc"
> >
> > -names is pointless when there is only one.
> The MUSB core driver has two interrupts, one is for MAC, another for DMA,
> but on MTK platform, there is only a MAC interrupt, here following the binding
> of MUSB core driver.

You should probably be listing the same interrupt number twice if 2
interrupts are combined.

> > > +Optional properties:
> > > + - extcon : external connector for VBUS and IDPIN changes detection,
> > > +   needed when supports dual-role mode.
> >
> > Don't use extcon for new bindings. The usb-connector binding should be
> > used instead.
> This is used to detect the changes of the IDPIN and VBUS, the change
> events are provided by other drivers, such as extcon-usb-gpio.c, and
> then switch MUSB controller to host or device mode, but the
> usb-connector can't detect these changes.

To repeat, do not use extcon binding for new bindings. It is poorly
designed as it reflects extcon driver needs, not a description of the
hardware. If you have ID on GPIO, then that belongs in a usb-connector
node because that GPIO goes to the connector. For Vbus, you should
have a vbus-supply in the connector and use a gpio-regulator if it is
GPIO controlled.

> > > + - vbus-supply : reference to the VBUS regulator, needed when supports
> > > +   dual-role mode.
> >
> > The controller is powered from Vbus? Probably not. This belongs in the
> > connector or maybe the phy (if the phy is powered from Vbus).
> The Vbus is used to provide 5V voltage to the connected device when the
> controller works as host mode.

I know what Vbus is. Unless Vbus is providing power to the host
controller, putting the Vbus supply in the controller node is not a
accurate representation of the hardware.

Rob