Re: [PATCH] usb: dwc3: avoid probe deferral when USB power supply is not available

[Elson Serrao <elson.serrao@oss.qualcomm.com>]

On 4/7/2026 4:24 PM, Elson Serrao wrote:
> The dwc3 driver currently defers probe if the USB power supply is not yet
> registered. On some platforms, even though charging and power supply
> functionality is available during normal operation, there may exist
> minimal booting modes (such as recovery or diagnostic environments) where
> the relevant USB power supply device is not registered. In such cases,
> probe deferral prevents USB gadget operation entirely.
> 
> USB data functionality for basic operation does not inherently depend on
> the power supply framework, which is only required for enforcing VBUS
> current control. The configured VBUS current limit is typically enforced
> through the charger or PMIC power path. When charging functionality is
> unavailable, applying a current limit has no practical effect, reducing
> the benefit of strict probe-time enforcement in these environments.
> 
> Instead of deferring probe, register a power supply notifier when the
> USB power supply is not yet available. Cache the requested VBUS current
> limit and apply it once the matching power supply becomes available, as
> notified through the registered callback.
> 
> Signed-off-by: Elson Serrao <elson.serrao@oss.qualcomm.com>
> ---
>  drivers/usb/dwc3/core.c   | 82 ++++++++++++++++++++++++++++++++-------
>  drivers/usb/dwc3/core.h   |  4 ++
>  drivers/usb/dwc3/gadget.c | 10 ++++-
>  3 files changed, 80 insertions(+), 16 deletions(-)
> 


Hi Thinh,

Just a gentle reminder about this patch.
Please let me know if any changes are needed.

Thanks,
Elson

[...]

> +	if (!dwc->usb_psy) {
> +		spin_unlock_irqrestore(&dwc->lock, flags);
> +		dev_dbg(dwc->dev, "Stored VBUS draw: %u mA (power supply not ready)\n", mA);
>  		return -EOPNOTSUPP;
> +	}
>  
> -	dwc->current_limit = mA;
>  	schedule_work(&dwc->vbus_draw_work);
> +	spin_unlock_irqrestore(&dwc->lock, flags);
>  
>  	return 0;
>  }