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

Chunfeng Yun
2019-05-22T09:30:48Z

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?

>
> > 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
>