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

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Message-ID: <aYFMfPeeQusS1UR4@shlinux89>
Date: Tue, 3 Feb 2026 09:16:44 +0800
From: Peng Fan <peng.fan@....nxp.com>
To: Thinh Nguyen <Thinh.Nguyen@...opsys.com>
Cc: 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 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?

Regards
Peng