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

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Message-ID: <20260203002405.5wxsceuc47m6hrud@synopsys.com>
Date: Tue, 3 Feb 2026 00:24:08 +0000
From: Thinh Nguyen <Thinh.Nguyen@...opsys.com>
To: Xu Yang <xu.yang_2@....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>, Thinh Nguyen <Thinh.Nguyen@...opsys.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 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?

BR,
Thinh

>  
>  	unsigned		disable_scramble_quirk:1;
>  	unsigned		u2exit_lfps_quirk:1;
> diff --git a/drivers/usb/dwc3/glue.h b/drivers/usb/dwc3/glue.h
> index df86e14cb706ca509206677f644da2a7225b1b26..b428a9f4a32625e7331f8492a408f7c20c915825 100644
> --- a/drivers/usb/dwc3/glue.h
> +++ b/drivers/usb/dwc3/glue.h
> @@ -29,6 +29,8 @@ struct dwc3_properties {
>   *		be ignored by the DWC3 core, as they are managed by the glue
>   * @skip_core_init_mode: Skip the finial initialization of the target mode, as
>   *		it must be managed by the glue
> + * @core_may_lose_power: indicate the controller may not remain power during
> + *		system suspend/resume
>   * @properties: dwc3 software manage properties
>   */
>  struct dwc3_probe_data {
> @@ -36,6 +38,7 @@ struct dwc3_probe_data {
>  	struct resource *res;
>  	bool ignore_clocks_and_resets;
>  	bool skip_core_init_mode;
> +	bool core_may_lose_power;
>  	struct dwc3_properties properties;
>  };
>  
> 
> -- 
> 2.34.1
>