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

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Message-ID: <20260204015208.rpgp623pj37nldbm@synopsys.com>
Date: Wed, 4 Feb 2026 01:52:15 +0000
From: Thinh Nguyen <Thinh.Nguyen@...opsys.com>
To: Peng Fan <peng.fan@....nxp.com>
CC: Thinh Nguyen <Thinh.Nguyen@...opsys.com>, Xu Yang <xu.yang_2@....com>,
        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, Peng Fan wrote:
> 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.
> >
> >> +		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?
> 
> How about out_band_wakeup?
> 

IMHO, it's not as clear. It doesn't describe the problem or the action
to take. Can we use needs_full_reinit?

Thanks,
Thinh