linux-kernel - Re: [PATCH v1] usb: dwc3: core: Defer the probe until USB power supply ready

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Message-ID: <20250115012319.td2wh6jwv6q3ujda@synopsys.com>
Date: Wed, 15 Jan 2025 01:23:29 +0000
From: Thinh Nguyen <Thinh.Nguyen@...opsys.com>
To: Kyle Tso <kyletso@...gle.com>
CC: Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "raychi@...gle.com" <raychi@...gle.com>,
        "badhri@...gle.com" <badhri@...gle.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "royluo@...gle.com" <royluo@...gle.com>,
        "bvanassche@....org" <bvanassche@....org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: Re: [PATCH v1] usb: dwc3: core: Defer the probe until USB power
 supply ready

On Tue, Jan 14, 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@...r.kernel.org
> Signed-off-by: Kyle Tso <kyletso@...gle.com>
> ---
> Note: This is a follow-up of https://urldefense.com/v3/__https://lore.kernel.org/all/20240804084612.2561230-1-kyletso@google.com/__;!!A4F2R9G_pg!ZTwcKSid-i7kN4_N622H1QDeC3jzi0uCKRqjzrTNStFGr8guMe3xY0EF30CnGGPyBK25ZCGgUc_Wg3koxwqa$ 
> ---
>  drivers/usb/dwc3/core.c | 10 +++++++---
>  1 file changed, 7 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
> index 7578c5133568..1550c39e792a 100644
> --- a/drivers/usb/dwc3/core.c
> +++ b/drivers/usb/dwc3/core.c
> @@ -1669,7 +1669,7 @@ static void dwc3_get_software_properties(struct dwc3 *dwc)
>  	}
>  }
>  
> -static void dwc3_get_properties(struct dwc3 *dwc)
> +static int dwc3_get_properties(struct dwc3 *dwc)

It doesn't make sense for dwc3_get_properties() to return -EPROBE_DEFER.

>  {
>  	struct device		*dev = dwc->dev;
>  	u8			lpm_nyet_threshold;
> @@ -1724,7 +1724,7 @@ static void dwc3_get_properties(struct dwc3 *dwc)
>  	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");
> +			return dev_err_probe(dev, -EPROBE_DEFER, "couldn't get usb power supply\n");
>  	}

Move this logic (including power_supply_get_by_name()) outside of
dwc3_get_properties(). It doesn't belong here.

Thanks,
Thinh

>  
>  	dwc->has_lpm_erratum = device_property_read_bool(dev,
> @@ -1847,6 +1847,8 @@ static void dwc3_get_properties(struct dwc3 *dwc)
>  	dwc->imod_interval = 0;
>  
>  	dwc->tx_fifo_resize_max_num = tx_fifo_resize_max_num;
> +
> +	return 0;
>  }
>  
>  /* check whether the core supports IMOD */
> @@ -2181,7 +2183,9 @@ static int dwc3_probe(struct platform_device *pdev)
>  	dwc->regs	= regs;
>  	dwc->regs_size	= resource_size(&dwc_res);
>  
> -	dwc3_get_properties(dwc);
> +	ret = dwc3_get_properties(dwc);
> +	if (ret)
> +		return ret;
>  
>  	dwc3_get_software_properties(dwc);
>  
> -- 
> 2.47.1.688.g23fc6f90ad-goog
>