linux-kernel - Re: [RFC/PATCH 2/2] phy: rockchip: usbdp: implement .set

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Message-ID: <aHf6LGtYiLNFRQDF-jkeeping@inmusicbrands.com>
Date: Wed, 16 Jul 2025 20:14:52 +0100
From: John Keeping <jkeeping@...usicbrands.com>
To: Heiko Stuebner <heiko@...ech.de>
Cc: linux-rockchip@...ts.infradead.org,
	Kishon Vijay Abraham I <kishon@...nel.org>,
	Neil Armstrong <neil.armstrong@...aro.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-usb@...r.kernel.org,
	Sebastian Reichel <sebastian.reichel@...labora.com>,
	linux-kernel@...r.kernel.org, Vinod Koul <vkoul@...nel.org>,
	Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
	linux-phy@...ts.infradead.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [RFC/PATCH 2/2] phy: rockchip: usbdp: implement .set_mode

On Tue, Jul 15, 2025 at 12:35:47PM +0200, Heiko Stuebner wrote:
> Am Donnerstag, 10. Juli 2025, 17:22:50 Mitteleuropäische Sommerzeit schrieb John Keeping:
> > When the orientation of a type C cable changes, usbdp set the new
> > configuration in its internal state but does not write this to the
> > hardware.
> > 
> > Make use of phy_ops::set_mode to write this new state.  This should be
> > called by the USB controller when it is notified of a role change
> > (assuming it is acting as the role switch) and will be called at a point
> > when the controller does not expect the phy to be operating normally.
> > 
> > Signed-off-by: John Keeping <jkeeping@...usicbrands.com>
> 
> with the comments from Ondrej in [0] the whole thing seems to be
> slightly more complex
> 
> 
> [0] https://patchwork.kernel.org/project/linux-arm-kernel/patch/20250225184519.3586926-3-heiko@sntech.de/

I spent some more time looking at this and have found what looks like
the vendor kernel's approach to this issue [1].  It seems that Rockchip
set the autosuspend time to 100ms and hope that is sufficiently short to
allow the controller to suspend whenever a cable is unplugged.

[1] https://github.com/rockchip-linux/kernel/commit/5ac62b80f7471ee9858ab0459af07180de938b51

Having experimented some more, I was able to do something similar
without needing any changes to the phy driver by applying the changes
below on top of patch 1/2 in this thread.  This depends on runtime PM to
ensure the controller is suspended whenever a cable is unplugged, but if
CONFIG_PM is enabled then it should address those concerns because the
controller will be shutdown and the phy configured via phy_init() in the
normal sequence.

It sounds like Thinh doesn't like this approach, but if the requirement
is for the controller to be shutdown and restarted whenever the
orientation changes I don't think we can avoid some changes in dwc3.

--- >8 ---
diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
index 6573cca0eeaf5..b707afd38cc27 100644
--- a/drivers/usb/dwc3/core.c
+++ b/drivers/usb/dwc3/core.c
@@ -199,6 +199,10 @@ static void __dwc3_set_mode(struct work_struct *work)
 		dwc3_otg_update(dwc, 1);
 		break;
 	default:
+		if (dwc->force_suspended) {
+			pm_runtime_force_resume(dwc->dev);
+			dwc->force_suspended = 0;
+		}
 		break;
 	}
 
@@ -272,6 +276,9 @@ static void __dwc3_set_mode(struct work_struct *work)
 		dwc3_otg_update(dwc, 0);
 		break;
 	default:
+		ret = pm_runtime_force_suspend(dwc->dev);
+		if (!ret)
+			dwc->force_suspended = 1;
 		break;
 	}
 
@@ -2485,7 +2492,7 @@ static int dwc3_suspend_common(struct dwc3 *dwc, pm_message_t msg)
 		dwc3_core_exit(dwc);
 		break;
 	default:
-		/* do nothing */
+		dwc3_core_exit(dwc);
 		break;
 	}
 
@@ -2552,7 +2559,9 @@ static int dwc3_resume_common(struct dwc3 *dwc, pm_message_t msg)
 
 		break;
 	default:
-		/* do nothing */
+		ret = dwc3_core_init_for_resume(dwc);
+		if (ret)
+			return ret;
 		break;
 	}
 
diff --git a/drivers/usb/dwc3/core.h b/drivers/usb/dwc3/core.h
index d5b985fa12f4d..7e1d480c59ae1 100644
--- a/drivers/usb/dwc3/core.h
+++ b/drivers/usb/dwc3/core.h
@@ -1390,6 +1390,7 @@ struct dwc3 {
 	unsigned		sys_wakeup:1;
 	unsigned		wakeup_configured:1;
 	unsigned		suspended:1;
+	unsigned		force_suspended:1;
 	unsigned		susphy_state:1;
 
 	u16			imod_interval;
diff --git a/drivers/usb/dwc3/drd.c b/drivers/usb/dwc3/drd.c
index 8f427afa8eb93..16aac8384ca3d 100644
--- a/drivers/usb/dwc3/drd.c
+++ b/drivers/usb/dwc3/drd.c
@@ -461,6 +461,7 @@ static int dwc3_usb_role_switch_set(struct usb_role_switch *sw,
 		break;
 	}
 
+	flush_work(&dwc->drd_work);
 	dwc3_set_mode(dwc, mode);
 	return 0;
 }