RE: [PATCH v5 4/6] usb: roles: add API to get usb_role_switch by node

[Biju Das <biju.das@bp.renesas.com>]

Hi Chunfeng Yun,

Thanks for the feedback.

> Subject: RE: [PATCH v5 4/6] usb: roles: add API to get usb_role_switch by
> node
> 
> Hi Biju,
> On Wed, 2019-05-22 at 08:05 +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 09:45:46AM +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
> > >
> > > We need to understand why is that happening?
> > >
> >
> > Form the stack trace  the parent node is "parent_node=hd3ss3220@47" ,
> instead of the "connector" node.
> > That is the reason for the above error.
> >
> > [    2.442429]  of_graph_get_next_endpoint.part.0+0x28/0x168
> > [    2.447889]  of_fwnode_graph_get_next_endpoint+0x5c/0xb0
> > [    2.453267]  fwnode_graph_get_next_endpoint+0x20/0x30
> > [    2.458374]  device_connection_find_match+0x74/0x1a0
> > [    2.463399]  usb_role_switch_get+0x20/0x28
> > [    2.467542]  hd3ss3220_probe+0xc4/0x218
> >
> > The use case is
> >
> > &i2c0 {
> > 	hd3ss3220@47 {
> >                  	compatible = "ti,hd3ss3220";
> >
> >                  	usb_con: connector {
> >                           		compatible = "usb-c-connector";
> >                          		port {
> >                                 		 hd3ss3220_ep: endpoint {
> >                                         			remote-endpoint =
> <&usb3_role_switch>;
> >                                 		};
> >                          		};
> >                 	 };
> > 	 };
> > };
> >
> > &usb3_peri0 {
> >          companion = <&xhci0>;
> >          usb-role-switch;
> >
> >          port {
> >                 usb3_role_switch: endpoint {
> >                         remote-endpoint = <&hd3ss3220_ep>;
> >                  };
> >          };
> > };
> >
> > Q1) How do we modify the usb_role_switch_get() function to search
> > Child(connector) and child's endpoint?
> How about firstly finding connector node in fwnode_graph_devcon_match(),
> then search each endpoint?

 I have done a quick prototyping with the changes you suggested and it works.

-       struct fwnode_handle *ep;
+       struct fwnode_handle *ep,*child,*tmp = fwnode; 
 
-       fwnode_graph_for_each_endpoint(fwnode, ep) {
+       child = fwnode_get_named_child_node(fwnode, "connector");
+       if (child)
+               tmp = child;
+
+       fwnode_graph_for_each_endpoint(tmp, ep) {

Form the stack trace  the parent node is "parent_node= connector" .

[    2.440922]  of_graph_get_next_endpoint.part.0+0x28/0x168
[    2.446381]  of_fwnode_graph_get_next_endpoint+0x5c/0xb0
[    2.451758]  fwnode_graph_get_next_endpoint+0x20/0x30
[    2.456866]  device_connection_find_match+0x84/0x1c0
[    2.461888]  usb_role_switch_get+0x20/0x28

Heikki, 
Are you ok  with the above changes?

Regards,
Biju
> >
> > > It looks like we have an issue somewhere in the code, and instead of
> > > fixing that, you are working around it. Let's not do that.
> >
> > OK.
> >
> > Regards,
> > Biju
> >
> 

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