linux-kernel - [PATCH] usb: dwc3: Prioritize extcon over USB role switching API

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Date:   Mon, 31 Jan 2022 11:21:02 -0800
From:   Andrey Smirnov <andrew.smirnov@...il.com>
To:     Felipe Balbi <balbi@...nel.org>
Cc:     Andrey Smirnov <andrew.smirnov@...il.com>,
        Thinh Nguyen <thinhn@...opsys.com>, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] usb: dwc3: Prioritize extcon over USB role switching API

It is necessary that:

   ROLE_SWITCH && device_property_read_bool(dwc->dev, "usb-role-switch")

is true in order for dwc3_get_dr_mode() to _not_ force us from OTG to
PERIPHERAL mode here:

   if (mode == USB_DR_MODE_OTG &&
       (!IS_ENABLED(CONFIG_USB_ROLE_SWITCH) ||
        !device_property_read_bool(dwc->dev, "usb-role-switch")) &&
	!DWC3_VER_IS_PRIOR(DWC3, 330A))
	mode = USB_DR_MODE_PERIPHERAL;

and dwc3_drd_init() to be called later in dwc3_core_init_mode(). So,
to avoid always ignoring extcon device returned by dwc3_get_extcon()
change dwc3_drd_init() to check and use it first, before checking if
dwc3_setup_role_switch() should be called.

Cc: Felipe Balbi <balbi@...nel.org>
Cc: Thinh Nguyen <thinhn@...opsys.com>
Cc: linux-usb@...r.kernel.org
Cc: linux-kernel@...r.kernel.org
Signed-off-by: Andrey Smirnov <andrew.smirnov@...il.com>
---

Hopefully I didn't miss something important making this patch
unnecessary. Don't know if this is a good solution or not, part of me
thinks than maybe changing the aforementioned code in
dwc3_get_dr_mode() to account for extcon wopuld be
simpler/better. Happy to rework this.

 drivers/usb/dwc3/drd.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/usb/dwc3/drd.c b/drivers/usb/dwc3/drd.c
index e2b68bb770d1..835bd0be87d5 100644
--- a/drivers/usb/dwc3/drd.c
+++ b/drivers/usb/dwc3/drd.c
@@ -579,12 +579,7 @@ int dwc3_drd_init(struct dwc3 *dwc)
 	if (IS_ERR(dwc->edev))
 		return PTR_ERR(dwc->edev);

-	if (ROLE_SWITCH &&
-	    device_property_read_bool(dwc->dev, "usb-role-switch")) {
-		ret = dwc3_setup_role_switch(dwc);
-		if (ret < 0)
-			return ret;
-	} else if (dwc->edev) {
+	if (dwc->edev) {
 		dwc->edev_nb.notifier_call = dwc3_drd_notifier;
 		ret = extcon_register_notifier(dwc->edev, EXTCON_USB_HOST,
 					       &dwc->edev_nb);
@@ -594,6 +589,11 @@ int dwc3_drd_init(struct dwc3 *dwc)
 		}

 		dwc3_drd_update(dwc);
+	} else if (ROLE_SWITCH &&
+		   device_property_read_bool(dwc->dev, "usb-role-switch")) {
+		ret = dwc3_setup_role_switch(dwc);
+		if (ret < 0)
+			return ret;
 	} else {
 		dwc3_set_prtcap(dwc, DWC3_GCTL_PRTCAP_OTG);
 		dwc->current_dr_role = DWC3_GCTL_PRTCAP_OTG;
--
2.25.1