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

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Message-ID: <e0e36d42-5479-fd8c-3868-384161031738@synopsys.com>
Date:   Thu, 3 Feb 2022 02:54:13 +0000
From:   Thinh Nguyen <Thinh.Nguyen@...opsys.com>
To:     Andrey Smirnov <andrew.smirnov@...il.com>,
        Felipe Balbi <balbi@...nel.org>
CC:     "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] usb: dwc3: Prioritize extcon over USB role switching API

Andrey Smirnov wrote:
> 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.

The driver either use extcon or usb-role-switch. It doesn't make sense to
enable usb-role-switch for extcon just so the driver doesn't default
the dr_mode to peripheral.

Perhaps, this is what you're looking for? (code is not tested)

diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
index bffd719b8b52..a52331ea7a0d 100644
--- a/drivers/usb/dwc3/core.c
+++ b/drivers/usb/dwc3/core.c
@@ -86,7 +86,7 @@ static int dwc3_get_dr_mode(struct dwc3 *dwc)
                 * mode. If the controller supports DRD but the dr_mode is not
                 * specified or set to OTG, then set the mode to peripheral.
                 */
-               if (mode == USB_DR_MODE_OTG &&
+               if (mode == USB_DR_MODE_OTG && !dwc->edev &&
                    (!IS_ENABLED(CONFIG_USB_ROLE_SWITCH) ||
                     !device_property_read_bool(dwc->dev, "usb-role-switch")) &&
                    !DWC3_VER_IS_PRIOR(DWC3, 330A))
@@ -1715,6 +1715,13 @@ static int dwc3_probe(struct platform_device *pdev)
                goto err2;
        }
 
+       dwc->edev = dwc3_get_extcon(dwc);
+       if (IS_ERR(dwc->edev)) {
+               ret = PTR_ERR(dwc->edev);
+               dev_err(dwc->dev, "failed to get extcon %d\n", ret);
+               goto err3;
+       }
+
        ret = dwc3_get_dr_mode(dwc);
        if (ret)
                goto err3;
diff --git a/drivers/usb/dwc3/drd.c b/drivers/usb/dwc3/drd.c
index 63089c7fb530..d02fcfdc74db 100644
--- a/drivers/usb/dwc3/drd.c
+++ b/drivers/usb/dwc3/drd.c
@@ -585,16 +585,7 @@ int dwc3_drd_init(struct dwc3 *dwc)
 {
        int ret, irq;
 
-       dwc->edev = dwc3_get_extcon(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);
@@ -604,6 +595,11 @@ 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);