usb: chipidea: core: add sysfs group

Sometimes, the user needs to adjust some properties for controllers, eg
the role for controller, we add sysfs group for them.

The attribute 'role' is used to switch host/gadget role dynamically, the
uewr can read the current role, and write the other role compare to
current one to finish the switch.

Signed-off-by: Peter Chen <[e-mail]>

Documentation/ABI/testing/sysfs-platform-chipidea-usb2

···
+What:		/sys/bus/platform/devices/ci_hdrc.0/role
+Date:		Mar 2017
+Contact:	Peter Chen <[e-mail]>
+Description:
+		It returns string "gadget" or "host" when read it, it indicates
+		current controller role.
+
+		It will do role switch when write "gadget" or "host" to it.
+		Only controller at dual-role configuration supports writing.

drivers/usb/chipidea/core.c

···
 	}
 }
 
+static ssize_t ci_role_show(struct device *dev, struct device_attribute *attr,
+			  char *buf)
+{
+	struct ci_hdrc *ci = dev_get_drvdata(dev);
+
+	return sprintf(buf, "%s\n", ci_role(ci)->name);
+}
+
+static ssize_t ci_role_store(struct device *dev,
+		struct device_attribute *attr, const char *buf, size_t n)
+{
+	struct ci_hdrc *ci = dev_get_drvdata(dev);
+	enum ci_role role;
+	int ret;
+
+	if (!(ci->roles[CI_ROLE_HOST] && ci->roles[CI_ROLE_GADGET])) {
+		dev_warn(dev, "Current configuration is not dual-role, quit\n");
+		return -EPERM;
+	}
+
+	for (role = CI_ROLE_HOST; role < CI_ROLE_END; role++)
+		if (!strncmp(buf, ci->roles[role]->name,
+			     strlen(ci->roles[role]->name)))
+			break;
+
+	if (role == CI_ROLE_END || role == ci->role)
+		return -EINVAL;
+
+	pm_runtime_get_sync(dev);
+	disable_irq(ci->irq);
+	ci_role_stop(ci);
+	ret = ci_role_start(ci, role);
+	if (!ret && ci->role == CI_ROLE_GADGET)
+		ci_handle_vbus_change(ci);
+	enable_irq(ci->irq);
+	pm_runtime_put_sync(dev);
+
+	return (ret == 0) ? n : ret;
+}
+static DEVICE_ATTR(role, 0644, ci_role_show, ci_role_store);
+
+static struct attribute *ci_attrs[] = {
+	&dev_attr_role.attr,
+	NULL,
+};
+
+static struct attribute_group ci_attr_group = {
+	.attrs = ci_attrs,
+};
+
 static int ci_hdrc_probe(struct platform_device *pdev)
 {
 	struct device	*dev = &pdev->dev;
···
 		ci_hdrc_otg_fsm_start(ci);
 
 	device_set_wakeup_capable(&pdev->dev, true);
-
 	ret = dbg_create_files(ci);
-	if (!ret)
-		return 0;
+	if (ret)
+		goto stop;
 
+	ret = sysfs_create_group(&dev->kobj, &ci_attr_group);
+	if (ret)
+		goto remove_debug;
+
+	return 0;
+
+remove_debug:
+	dbg_remove_files(ci);
 stop:
 	ci_role_destroy(ci);
 deinit_phy:
···
 	}
 
 	dbg_remove_files(ci);
+	sysfs_remove_group(&ci->dev->kobj, &ci_attr_group);
 	ci_role_destroy(ci);
 	ci_hdrc_enter_lpm(ci, true);
 	ci_usb_phy_exit(ci);

drivers/usb/chipidea/udc.c

···
 	 */
 	if (ci->is_otg)
 		hw_write_otgsc(ci, OTGSC_BSVIE | OTGSC_BSVIS, OTGSC_BSVIS);
+
+	ci->vbus_active = 0;
 }
 
 /**