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

[Heikki Krogerus <heikki.krogerus@linux.intel.com>]

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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@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?

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.

thanks,

-- 
heikki

[-- Attachment #2: 0001-device-connection-Add-fwnode_connection_find_match.patch --]
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From 18a15ef54f2d88b04ce851d9428cda6697a66fb2 Mon Sep 17 00:00:00 2001
From: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Date: Wed, 22 May 2019 16:43:41 +0300
Subject: [PATCH 1/2] device connection: Add fwnode_connection_find_match()

The fwnode_connection_find_match() function is exactly the
same as device_connection_find_match(), except it takes
struct fwnode_handle as parameter instead of struct device.
That allows locating device connections before the device
entries have been created.

Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
---
 drivers/base/devcon.c  | 33 +++++++++++++++++++++++++--------
 include/linux/device.h | 10 +++++++---
 2 files changed, 32 insertions(+), 11 deletions(-)

diff --git a/drivers/base/devcon.c b/drivers/base/devcon.c
index 04db9ae235e4..8311b70bbca2 100644
--- a/drivers/base/devcon.c
+++ b/drivers/base/devcon.c
@@ -12,9 +12,6 @@
 static DEFINE_MUTEX(devcon_lock);
 static LIST_HEAD(devcon_list);
 
-typedef void *(*devcon_match_fn_t)(struct device_connection *con, int ep,
-				   void *data);
-
 static void *
 fwnode_graph_devcon_match(struct fwnode_handle *fwnode, const char *con_id,
 			  void *data, devcon_match_fn_t match)
@@ -38,6 +35,28 @@ fwnode_graph_devcon_match(struct fwnode_handle *fwnode, const char *con_id,
 	return NULL;
 }
 
+/**
+ * fwnode_connection_find_match - Find connection from a device node
+ * @fwnode: Device node with the connection
+ * @con_id: Identifier for the connection
+ * @data: Data for the match function
+ * @match: Function to check and convert the connection description
+ *
+ * Find a connection with unique identifier @con_id between @fwnode and another
+ * device node. @match will be used to convert the connection description to
+ * data the caller is expecting to be returned.
+ */
+void *fwnode_connection_find_match(struct fwnode_handle *fwnode,
+				   const char *con_id, void *data,
+				   devcon_match_fn_t match)
+{
+	if (!fwnode || !match)
+		return NULL;
+
+	return fwnode_graph_devcon_match(fwnode, con_id, data, match);
+}
+EXPORT_SYMBOL_GPL(fwnode_connection_find_match);
+
 /**
  * device_connection_find_match - Find physical connection to a device
  * @dev: Device with the connection
@@ -61,11 +80,9 @@ void *device_connection_find_match(struct device *dev, const char *con_id,
 	if (!match)
 		return NULL;
 
-	if (fwnode) {
-		ret = fwnode_graph_devcon_match(fwnode, con_id, data, match);
-		if (ret)
-			return ret;
-	}
+	ret = fwnode_connection_find_match(fwnode, con_id, data, match);
+	if (ret)
+		return ret;
 
 	mutex_lock(&devcon_lock);
 
diff --git a/include/linux/device.h b/include/linux/device.h
index 72a6260f2b4d..04ca902d24dc 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -772,10 +772,14 @@ struct device_connection {
 	struct list_head	list;
 };
 
+typedef void *(*devcon_match_fn_t)(struct device_connection *con, int ep,
+				   void *data);
+
+void *fwnode_connection_find_match(struct fwnode_handle *fwnode,
+				   const char *con_id, void *data,
+				   devcon_match_fn_t match);
 void *device_connection_find_match(struct device *dev, const char *con_id,
-				void *data,
-				void *(*match)(struct device_connection *con,
-					       int ep, void *data));
+				   void *data, devcon_match_fn_t match);
 
 struct device *device_connection_find(struct device *dev, const char *con_id);
 
-- 
2.20.1


[-- Attachment #3: 0002-usb-roles-Add-fwnode_usb_role_switch_get-function.patch --]
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From 9eaa446c507780a6f9d0a1cc12c04e87a3bafcf3 Mon Sep 17 00:00:00 2001
From: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Date: Wed, 22 May 2019 16:43:41 +0300
Subject: [PATCH 2/2] usb: roles: Add fwnode_usb_role_switch_get() function

The fwnode_usb_role_switch_get() function is exactly the
same as usb_role_switch_get(), except that it takes struct
fwnode_handle as parameter instead of struct device.

Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
---
 drivers/usb/roles/class.c | 20 ++++++++++++++++++++
 include/linux/usb/role.h  |  1 +
 2 files changed, 21 insertions(+)

diff --git a/drivers/usb/roles/class.c b/drivers/usb/roles/class.c
index f45d8df5cfb8..aab795b54c7f 100644
--- a/drivers/usb/roles/class.c
+++ b/drivers/usb/roles/class.c
@@ -135,6 +135,26 @@ struct usb_role_switch *usb_role_switch_get(struct device *dev)
 }
 EXPORT_SYMBOL_GPL(usb_role_switch_get);
 
+/**
+ * fwnode_usb_role_switch_get - Find USB role switch linked with the caller
+ * @fwnode: The caller device node
+ *
+ * This is similar to the usb_role_switch_get() function above, but it searches
+ * the switch using fwnode instead of device entry.
+ */
+struct usb_role_switch *fwnode_usb_role_switch_get(struct fwnode_handle *fwnode)
+{
+	struct usb_role_switch *sw;
+
+	sw = fwnode_connection_find_match(fwnode, "usb-role-switch", NULL,
+					  usb_role_switch_match);
+	if (!IS_ERR_OR_NULL(sw))
+		WARN_ON(!try_module_get(sw->dev.parent->driver->owner));
+
+	return sw;
+}
+EXPORT_SYMBOL_GPL(fwnode_usb_role_switch_get);
+
 /**
  * usb_role_switch_put - Release handle to a switch
  * @sw: USB Role Switch
diff --git a/include/linux/usb/role.h b/include/linux/usb/role.h
index c05ffa6abda9..6abb04df255c 100644
--- a/include/linux/usb/role.h
+++ b/include/linux/usb/role.h
@@ -45,6 +45,7 @@ struct usb_role_switch_desc {
 int usb_role_switch_set_role(struct usb_role_switch *sw, enum usb_role role);
 enum usb_role usb_role_switch_get_role(struct usb_role_switch *sw);
 struct usb_role_switch *usb_role_switch_get(struct device *dev);
+struct usb_role_switch *fwnode_usb_role_switch_get(struct fwnode_handle *node);
 void usb_role_switch_put(struct usb_role_switch *sw);
 
 struct usb_role_switch *
-- 
2.20.1