linux-kernel - RE: [PATCH v5 4/6] usb: roles: add API to get usb_role

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Message-ID: <OSBPR01MB2103C4C8920C40E42BC1B2A9B8060@OSBPR01MB2103.jpnprd01.prod.outlook.com>
Date:   Mon, 20 May 2019 09:45:46 +0000
From:   Biju Das <biju.das@...renesas.com>
To:     Heikki Krogerus <heikki.krogerus@...ux.intel.com>
CC:     Chunfeng Yun <chunfeng.yun@...iatek.com>,
        Rob Herring <robh+dt@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Mark Rutland <mark.rutland@....com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Adam Thomson <Adam.Thomson.Opensource@...semi.com>,
        Li Jun <jun.li@....com>,
        Badhri Jagan Sridharan <badhri@...gle.com>,
        Hans de Goede <hdegoede@...hat.com>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        Min Guo <min.guo@...iatek.com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-mediatek@...ts.infradead.org" 
        <linux-mediatek@...ts.infradead.org>,
        Linus Walleij <linus.walleij@...aro.org>
Subject: RE: [PATCH v5 4/6] usb: roles: add API to get usb_role_switch by node



Hi Heikki,

Thanks for the feedback.

> Subject: Re: [PATCH v5 4/6] usb: roles: add API to get usb_role_switch by
> node
> 
> On Mon, May 20, 2019 at 08:06:41AM +0000, Biju Das wrote:
> > Hi Heikki,
> >
> > > Subject: Re: [PATCH v5 4/6] usb: roles: add API to get
> > > usb_role_switch by node
> > >
> > > On Mon, May 20, 2019 at 10:39:11AM +0800, Chunfeng Yun wrote:
> > > > Hi,
> > > > On Fri, 2019-05-17 at 16:05 +0300, Heikki Krogerus wrote:
> > > > > Hi,
> > > > >
> > > > > On Fri, May 17, 2019 at 01:37:36PM +0300, Heikki Krogerus wrote:
> > > > > > On Tue, May 14, 2019 at 04:47:21PM +0800, Chunfeng Yun wrote:
> > > > > > > Add fwnode_usb_role_switch_get() to make easier to get
> > > > > > > usb_role_switch by fwnode which register it.
> > > > > > > It's useful when there is not device_connection registered
> > > > > > > between two drivers and only knows the fwnode which register
> > > > > > > usb_role_switch.
> > > > > > >
> > > > > > > Signed-off-by: Chunfeng Yun <chunfeng.yun@...iatek.com>
> > > > > > > Tested-by: Biju Das <biju.das@...renesas.com>
> > > > > >
> > > > > > Acked-by: Heikki Krogerus <heikki.krogerus@...ux.intel.com>
> > > > >
> > > > > Hold on. I just noticed Rob's comment on patch 2/6, where he
> > > > > points out that you don't need to use device graph since the
> > > > > controller is the parent of the connector. Doesn't that mean you
> > > > > don't really need this API?
> > > > No, I still need it.
> > > > The change is about the way how to get fwnode; when use device
> > > > graph, get fwnode by of_graph_get_remote_node(); but now will get
> > > > fwnode by of_get_parent();
> > >
> > > OK, I get that, but I'm still not convinced about if something like
> > > this function is needed at all. I also have concerns regarding how
> > > you are using the function. I'll explain in comment to the patch 5/6 in this
> series...
> >
> > FYI, Currently  I am also using this api in my patch series.
> > https://patchwork.kernel.org/patch/10944637/
> 
> Yes, and I have the same question for you I jusb asked in comment I added
> to the patch 5/6 of this series. Why isn't usb_role_switch_get() enough?

Currently no issue. It will work with this api as well, since the port node is part of controller node.
For eg:-
https://patchwork.kernel.org/patch/10944627/

However if any one adds port node inside the connector node, then this api may won't work as expected.
Currently I get below error

[    2.299703] OF: graph: no port node found in /soc/i2c@...00000/hd3ss3220@47

For eg:-

	hd3ss3220@47 {
		compatible = "ti,hd3ss3220";
		...
		....
		usb_con: connector {
                                     ....
                                     ....
			port {
				hd3ss3220_ep: endpoint@0 {
					reg = <0>;
					remote-endpoint = <&usb3peri_role_switch>;
				};
			};
		};
	};

Regards,
Biju