linux-kernel - Re: [PATCH 2/3] usb: dwc3: add may_lose

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Message-ID: <btmi4jypvq4qxe3inmex7zprgdjp4ug23kbirrllfeqc4662n6@uva5i26bfngs>
Date: Wed, 4 Feb 2026 13:47:39 +0800
From: Xu Yang <xu.yang_2@....com>
To: Thinh Nguyen <Thinh.Nguyen@...opsys.com>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
	Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, 
	Conor Dooley <conor+dt@...nel.org>, Shawn Guo <shawnguo@...nel.org>, 
	Sascha Hauer <s.hauer@...gutronix.de>, Pengutronix Kernel Team <kernel@...gutronix.de>, 
	Fabio Estevam <festevam@...il.com>, Frank Li <frank.li@....com>, Li Jun <jun.li@....com>, 
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>, "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>, 
	"imx@...ts.linux.dev" <imx@...ts.linux.dev>, 
	"linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/3] usb: dwc3: add may_lose_power flag

On Tue, Feb 03, 2026 at 12:24:08AM +0000, Thinh Nguyen wrote:
> On Mon, Feb 02, 2026, Xu Yang wrote:
> > The current design assumes that the controller remains powered
> > when wakeup is enabled. However, some SoCs provide wakeup
> > capability even when the controller itself is powered down, using
> > separate dedicated wakeup logic. This allows additional power
> > savings, but requires the controller to be fully re‑initialized
> > after system resume.
> > 
> > To support these SoCs, introduce a flag to track the controller’s
> > power state and use it throughout the suspend/resume flow.
> > 
> > Signed-off-by: Xu Yang <xu.yang_2@....com>
> > ---
> >  drivers/usb/dwc3/core.c | 9 +++++++--
> >  drivers/usb/dwc3/core.h | 2 ++
> >  drivers/usb/dwc3/glue.h | 3 +++
> >  3 files changed, 12 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
> > index c07ffe82c85049364c38c7ba152aab0ff764d95e..9d4326da5ec7669fa714707fb24556723cab51b8 100644
> > --- a/drivers/usb/dwc3/core.c
> > +++ b/drivers/usb/dwc3/core.c
> > @@ -2314,6 +2314,9 @@ int dwc3_core_probe(const struct dwc3_probe_data *data)
> >  			goto err_exit_debugfs;
> >  	}
> >  
> > +	if (data->core_may_lose_power)
> 
> Can this be passed down as part of the dwc3_properties within the
> probe_data? I'm trying to consolidate all the dwc3 properties to one
> place.

Sure. Will do.

> 
> > +		dwc->may_lose_power = true;
> > +
> >  	pm_runtime_put(dev);
> >  
> >  	dma_set_max_seg_size(dev, UINT_MAX);
> > @@ -2462,7 +2465,8 @@ static int dwc3_suspend_common(struct dwc3 *dwc, pm_message_t msg)
> >  		dwc3_core_exit(dwc);
> >  		break;
> >  	case DWC3_GCTL_PRTCAP_HOST:
> > -		if (!PMSG_IS_AUTO(msg) && !device_may_wakeup(dwc->dev)) {
> > +		if (!PMSG_IS_AUTO(msg) &&
> > +		    (!device_may_wakeup(dwc->dev) || dwc->may_lose_power)) {
> >  			dwc3_core_exit(dwc);
> >  			break;
> >  		}
> > @@ -2525,7 +2529,8 @@ static int dwc3_resume_common(struct dwc3 *dwc, pm_message_t msg)
> >  		dwc3_gadget_resume(dwc);
> >  		break;
> >  	case DWC3_GCTL_PRTCAP_HOST:
> > -		if (!PMSG_IS_AUTO(msg) && !device_may_wakeup(dwc->dev)) {
> > +		if (!PMSG_IS_AUTO(msg) &&
> > +		    (!device_may_wakeup(dwc->dev) || dwc->may_lose_power)) {
> >  			ret = dwc3_core_init_for_resume(dwc);
> >  			if (ret)
> >  				return ret;
> > diff --git a/drivers/usb/dwc3/core.h b/drivers/usb/dwc3/core.h
> > index 08cc6f2b5c23631a752c77fd7394e5876c929f0a..5b1358f36490a001bc9e68139224f7be70a57995 100644
> > --- a/drivers/usb/dwc3/core.h
> > +++ b/drivers/usb/dwc3/core.h
> > @@ -1117,6 +1117,7 @@ struct dwc3_glue_ops {
> >   * @usb3_lpm_capable: set if hadrware supports Link Power Management
> >   * @usb2_lpm_disable: set to disable usb2 lpm for host
> >   * @usb2_gadget_lpm_disable: set to disable usb2 lpm for gadget
> > + * @may_lose_power: set to indicate the core may lose power during pm suspend
> >   * @disable_scramble_quirk: set if we enable the disable scramble quirk
> >   * @u2exit_lfps_quirk: set if we enable u2exit lfps quirk
> >   * @u2ss_inp3_quirk: set if we enable P3 OK for U2/SS Inactive quirk
> > @@ -1369,6 +1370,7 @@ struct dwc3 {
> >  	unsigned		usb3_lpm_capable:1;
> >  	unsigned		usb2_lpm_disable:1;
> >  	unsigned		usb2_gadget_lpm_disable:1;
> > +	unsigned		may_lose_power:1;
> 
> This name sounds like a quirk of a broken SoC.
> 
> Perhaps rename this to something such as power_lost_on_suspend or
> needs_full_reinit?

OK. will use needs_full_reinit.

Thanks,
Xu Yang