Re: [PATCH v2] usb: dwc3: core: Defer the probe until USB power supply ready

[Thinh Nguyen <Thinh.Nguyen@synopsys.com>]

On Wed, Jan 15, 2025, Kyle Tso wrote:
> Currently, DWC3 driver attempts to acquire the USB power supply only
> once during the probe. If the USB power supply is not ready at that
> time, the driver simply ignores the failure and continues the probe,
> leading to permanent non-functioning of the gadget vbus_draw callback.
> 
> Address this problem by delaying the dwc3 driver initialization until
> the USB power supply is registered.
> 
> Fixes: 6f0764b5adea ("usb: dwc3: add a power supply for current control")
> Cc: stable@vger.kernel.org
> Signed-off-by: Kyle Tso <kyletso@google.com>
> ---
> v1 -> v2:
> - get the power supply in a dedicated function
> 
> ---
>  drivers/usb/dwc3/core.c | 30 +++++++++++++++++++++---------
>  1 file changed, 21 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
> index 7578c5133568..dfa1b5fe48dc 100644
> --- a/drivers/usb/dwc3/core.c
> +++ b/drivers/usb/dwc3/core.c
> @@ -1684,8 +1684,6 @@ static void dwc3_get_properties(struct dwc3 *dwc)
>  	u8			tx_thr_num_pkt_prd = 0;
>  	u8			tx_max_burst_prd = 0;
>  	u8			tx_fifo_resize_max_num;
> -	const char		*usb_psy_name;
> -	int			ret;
>  
>  	/* default to highest possible threshold */
>  	lpm_nyet_threshold = 0xf;
> @@ -1720,13 +1718,6 @@ static void dwc3_get_properties(struct dwc3 *dwc)
>  
>  	dwc->sys_wakeup = device_may_wakeup(dwc->sysdev);
>  
> -	ret = device_property_read_string(dev, "usb-psy-name", &usb_psy_name);
> -	if (ret >= 0) {
> -		dwc->usb_psy = power_supply_get_by_name(usb_psy_name);
> -		if (!dwc->usb_psy)
> -			dev_err(dev, "couldn't get usb power supply\n");
> -	}
> -
>  	dwc->has_lpm_erratum = device_property_read_bool(dev,
>  				"snps,has-lpm-erratum");
>  	device_property_read_u8(dev, "snps,lpm-nyet-threshold",
> @@ -2129,6 +2120,23 @@ static int dwc3_get_num_ports(struct dwc3 *dwc)
>  	return 0;
>  }
>  
> +static struct power_supply *dwc3_get_usb_power_supply(struct dwc3 *dwc)
> +{
> +	struct power_supply *usb_psy;
> +	const char *usb_psy_name;
> +	int ret;
> +
> +	ret = device_property_read_string(dwc->dev, "usb-psy-name", &usb_psy_name);
> +	if (ret < 0)
> +		return NULL;
> +
> +	usb_psy = power_supply_get_by_name(usb_psy_name);
> +	if (!usb_psy)
> +		return ERR_PTR(-EPROBE_DEFER);
> +
> +	return usb_psy;
> +}
> +
>  static int dwc3_probe(struct platform_device *pdev)
>  {
>  	struct device		*dev = &pdev->dev;
> @@ -2185,6 +2193,10 @@ static int dwc3_probe(struct platform_device *pdev)
>  
>  	dwc3_get_software_properties(dwc);
>  
> +	dwc->usb_psy = dwc3_get_usb_power_supply(dwc);
> +	if (IS_ERR(dwc->usb_psy))
> +		return dev_err_probe(dev, PTR_ERR(dwc->usb_psy), "couldn't get usb power supply\n");
> +
>  	dwc->reset = devm_reset_control_array_get_optional_shared(dev);
>  	if (IS_ERR(dwc->reset)) {
>  		ret = PTR_ERR(dwc->reset);
> -- 
> 2.48.0.rc2.279.g1de40edade-goog
> 

Acked-by: Thinh Nguyen <Thinh.Nguyen@synopsys.com>

Thanks,
Thinh