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Subject: Re: [PATCH v5 4/6] usb: roles: add API to get usb_role_switch by
 node
From:   Chunfeng Yun <chunfeng.yun@mediatek.com>
To:     Heikki Krogerus <heikki.krogerus@linux.intel.com>
CC:     Biju Das <biju.das@bp.renesas.com>,
        Rob Herring <robh+dt@kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Matthias Brugger <matthias.bgg@gmail.com>,
        "Adam Thomson" <Adam.Thomson.Opensource@diasemi.com>,
        Li Jun <jun.li@nxp.com>,
        Badhri Jagan Sridharan <badhri@google.com>,
        Hans de Goede <hdegoede@redhat.com>,
        Andy Shevchenko <andy.shevchenko@gmail.com>,
        Min Guo <min.guo@mediatek.com>,
        "devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-usb@vger.kernel.org" <linux-usb@vger.kernel.org>,
        "linux-arm-kernel@lists.infradead.org" 
        <linux-arm-kernel@lists.infradead.org>,
        "linux-mediatek@lists.infradead.org" 
        <linux-mediatek@lists.infradead.org>,
        Linus Walleij <linus.walleij@linaro.org>
Date:   Wed, 22 May 2019 11:37:42 +0800
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On Tue, 2019-05-21 at 13:33 +0300, Heikki Krogerus wrote:
> On Tue, May 21, 2019 at 03:35:04PM +0800, Chunfeng Yun wrote:
> > Hi,
> > On Mon, 2019-05-20 at 09:45 +0000, Biju Das wrote:
> > > 
> > > 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@mediatek.com>
> > > > > > > > > > Tested-by: Biju Das <biju.das@bp.renesas.com>
> > > > > > > > >
> > > > > > > > > Acked-by: Heikki Krogerus <heikki.krogerus@linux.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@e6500000/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
> > 
> > I tested 3 cases:
> > 
> > case 1:
> > 
> > connector {
> >     compatible = "linux,typeb-conn-gpio", "usb-b-connector";
> >     label = "micro-USB";
> >     type = "micro";
> >     id-gpios = <&pio 12 GPIO_ACTIVE_HIGH>;
> >     vbus-supply = <&usb_p0_vbus>;
> > 
> >     port {
> >         bconn_ep: endpoint@0 {
> >             remote-endpoint = <&usb_role_sw>;
> >         };
> >     };
> > };
> > 
> > &mtu3 {
> >     usb-role-switch;
> > 
> >     port {
> >         usb_role_sw: endpoint@0 {
> >             remote-endpoint = <&bconn_ep>;
> >         };
> >     };
> > };
> > 
> > the driver of connector could use usb_role_switch_get(dev) to get
> > mtu3's USB Role Switch. (dev is the device of connector)
> > 
> > case 2:
> > 
> > &mtu3 {
> >     usb-role-switch;
> > 
> >     connector {
> >         compatible = "linux,typeb-conn-gpio", "usb-b-connector";
> >         label = "micro-USB";
> >         type = "micro";
> >         id-gpios = <&pio 12 GPIO_ACTIVE_HIGH>;
> >         vbus-supply = <&usb_p0_vbus>;
> >     };
> > };
> > 
> > the driver of connector using usb_role_switch_get(dev) failed to get
> > mtu3's USB Role Switch.
> > error log:
> > #OF: graph: no port node found in /usb@11271000/connector
> > this is because connector hasn't child node connected to remote
> > endpoint which register USB Role Switch
> > 
> > case 3:
> > 
> > rsw_iddig: role_sw_iddig {
> >     compatible = "linux,typeb-conn-gpio";
> >     status = "okay";
> > 
> >     connector {
> >         compatible = "usb-b-connector";
> >         label = "micro-USB";
> >         type = "micro";
> >         id-gpios = <&pio 12 GPIO_ACTIVE_HIGH>;
> >         vbus-supply = <&usb_p0_vbus>;
> > 
> >         port {
> >             bconn_ep: endpoint@0 {
> >                 remote-endpoint = <&usb_role_sw>;
> >             };
> >         };
> >     };
> > };
> > 
> > &mtu3 {
> >     usb-role-switch;
> > 
> >     port {
> >         usb_role_sw: endpoint@0 {
> >             remote-endpoint = <&bconn_ep>;
> >         };
> >     };
> > };
> > 
> > 
> > the driver of connector using usb_role_switch_get(dev) also failed to
> > get mtu3's USB Role Switch. Because usb_role_switch_get() only search
> > its child nodes (connector node), but not child's child (port node)
> > This case is the same as Biju's
> > 
> > Usually type-c is similar with case 3;
> > the next version v6 of this series will use case 2 as Rob suggested,
> > see [v5, 2/6]
> > 
> > for case 2, will need the new API fwnode_usb_role_switch_get();
> 
> Thanks for the explanation.
> 
> In this case, if I understood this correctly, the USB controller, which
> is also the role switch, is the parent of the connector. So shouldn't
> we simply consider that in the current API?
It's better if can be added into the current API.
I'll try it.
> 
> diff --git a/drivers/usb/roles/class.c b/drivers/usb/roles/class.c
> index f45d8df5cfb8..2f898167b99a 100644
> --- a/drivers/usb/roles/class.c
> +++ b/drivers/usb/roles/class.c
> @@ -125,6 +125,13 @@ struct usb_role_switch *usb_role_switch_get(struct device *dev)
>  {
>         struct usb_role_switch *sw;
> 
> +       /*
> +        * Simplest case is that a connector is looking for the controller,
> +        * which is its parent.
> +        */
> +       if (device_property_present(dev->parent, "usb-role-switch"))
> +               return to_role_switch(dev->parent);
> +
>         sw = device_connection_find_match(dev, "usb-role-switch", NULL,
>                                           usb_role_switch_match);
> 
> 
> > for case 3, use the new API, or need modify usb_role_switch_get();
> 
> I did not completely understand this case, but isn't it the same as
> case 2 in the end, after you change it as Rob suggested?
I'm afraid not, their bindings are different, see
connector/usb-connector.txt
> 
> 
> thanks,
>