Re: [RFC/PATCH 2/2] phy: rockchip: usbdp: implement .set_mode

John Keeping
2025-07-16T19:15:01Z

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@inmusicbrands.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;
}