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

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Date:   Mon, 7 Jan 2019 15:31:32 +0800
From:   Min Guo <min.guo@...iatek.com>
To:     Rob Herring <robh@...nel.org>
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 Fri, 2019-01-04 at 10:10 -0600, Rob Herring wrote:
> 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.

If only one interrupt is regisetred in driver, dose still need list the
same interrupt number twice in dtsi?

> > > > +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.

Sorry, I didn't find a common driver describing the usb-connector. Is
there any driver that I can refer to, specially the way to switch MUSB
controller between host and device mode?

> > > > + - 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.

I will put vbus-supply in usb-connector after implement it.

> Rob