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

From: Chunfeng Yun
Date: Sun May 26 2019 - 23:10:50 EST

On Fri, 2019-05-24 at 14:40 +0300, Heikki Krogerus wrote:
> On Thu, May 23, 2019 at 06:16:10PM +0800, Chunfeng Yun wrote:
> > Hi Heikki,
> > On Wed, 2019-05-22 at 17:26 +0300, Heikki Krogerus wrote:
> > > On Wed, May 22, 2019 at 10:55:17AM +0000, Biju Das wrote:
> > > > 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@xxxxxxxxxxxx>
> > > > > > > > > > > > > > > Tested-by: Biju Das <biju.das@xxxxxxxxxxxxxx>
> > > > > > > > > > > > > >
> > > > > > > > > > > > > > Acked-by: Heikki Krogerus
> > > > > > > > > > > > > > <heikki.krogerus@xxxxxxxxxxxxxxx>
> > > > > > > > > > > > >
> > > > > > > > > > > > > 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?
> > >
> > > Doesn't that mean that if we made fwnode_usb_role_switch_get() the way
> > > I proposed, there is no problem? You just find the "connector" child
> > > node in your driver, and pass that to fwnode_usb_role_switch_get():
> > >
> > > struct fwnode_handle *connector;
> > > ...
> > > connector = device_get_named_child_node(&client->dev, "connector");
> > > if (IS_ERR(connector))
> > > <do something>
> > >
> > > hd3ss3220->role_sw = fwnode_usb_role_switch_get(connector);
> > > ...
> > >
> > > The difference is that instead of just converting a device node of an
> > > usb role switch to the usb role switch, it works just like
> > > usb_role_switch_get(), just taking fwnode instead of device entry as
> > > parameter.
> > >
> > > I prepared the patches implementing fwnode_usb_role_switch_get() the
> > > way I though it needs to work for my own tests. Please find the
> > > patches attached.
> > I tested these patches, it didn't work for case as following:
> >
> > 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>;
> > };
> > };
> >
> > so I consider this case in the function fwnode_graph_devcon_match()
> > (based on your patches)
>
> IMO that case should be handled in USB role switch API initially, not
> in the device connection API. If there is another user for it one day,
> then we can move it to device connection API, but not before that.
Ok
>
> How about this on top of the two patches I sent:
I just test it, it works well.
I'll prepare a patch and put into this series.

>
> diff --git a/drivers/usb/roles/class.c b/drivers/usb/roles/class.c
> index aab795b54c7f..36ac9d181e09 100644
> --- a/drivers/usb/roles/class.c
> +++ b/drivers/usb/roles/class.c
> @@ -114,6 +114,19 @@ static void *usb_role_switch_match(struct device_connection *con, int ep,
> return dev ? to_role_switch(dev) : ERR_PTR(-EPROBE_DEFER);
> }
>
> +static struct usb_role_switch *
> +usb_role_switch_is_parent(struct fwnode_handle *parent)
> +{
> + struct device *dev;
> +
> + if (!parent || !fwnode_property_present(parent, "usb-role-switch"))
> + return NULL;
> +
> + dev = class_find_device(role_class, NULL, parent, switch_fwnode_match);
> +
> + return dev ? to_role_switch(dev) : ERR_PTR(-EPROBE_DEFER);
> +}
> +
> /**
> * usb_role_switch_get - Find USB role switch linked with the caller
> * @dev: The caller device
> @@ -125,6 +138,10 @@ struct usb_role_switch *usb_role_switch_get(struct device *dev)
> {
> struct usb_role_switch *sw;
>
> + sw = usb_role_switch_is_parent(fwnode_get_parent(dev_fwnode(dev)));
> + if (sw)
> + return sw;
Do we also need to get parent module before return?

Thanks.
> +
> sw = device_connection_find_match(dev, "usb-role-switch", NULL,
> usb_role_switch_match);
>
> @@ -146,6 +163,10 @@ struct usb_role_switch *fwnode_usb_role_switch_get(struct fwnode_handle *fwnode)
> {
> struct usb_role_switch *sw;
>
> + sw = usb_role_switch_is_parent(fwnode_get_parent(fwnode));
> + if (sw)
> + return sw;
> +
> sw = fwnode_connection_find_match(fwnode, "usb-role-switch", NULL,
> usb_role_switch_match);
> if (!IS_ERR_OR_NULL(sw))
>
>
> thanks,
>