Re: [PATCH v5 2/2] usb: dwc3: dwc3-generic-plat: Add Renesas R-Car Gen5 DWC3 xHCI USB controller glue

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] Missing 'maximum-speed' DT property incorrectly forces the controller into USB 2.0-only mode, overriding PHY-based detection.
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commit 0727bb2cc9c155e4d5497db94c337bc5b2603464
Author: Thanh Quan <thanh.quan.xn@renesas.com>
usb: dwc3: dwc3-generic-plat: Add Renesas R-Car Gen5 DWC3 xHCI USB controller glue

This commit extends the generic DWC3 platform driver with glue logic for
Renesas R-Car Gen5 USB controllers. It handles hardware initialization and
evaluates PHY presence alongside device tree properties to determine maximum
supported USB speeds.

> diff --git a/drivers/usb/dwc3/dwc3-generic-plat.c b/drivers/usb/dwc3/dwc3-generic-plat.c
> index ca69ac0eb07ce..3994a6d93b9de 100644
> --- a/drivers/usb/dwc3/dwc3-generic-plat.c
> +++ b/drivers/usb/dwc3/dwc3-generic-plat.c
[ ... ]
> @@ -71,6 +71,55 @@ static int dwc3_eic7700_init(struct dwc3_generic *dwc3g)
>  	return 0;
>  }
>  
> +static int dwc3_renesas_rcar_gen5_init(struct dwc3_generic *dwc3g)
> +{
> +	struct device *dev = dwc3g->dev;
> +	struct platform_device *pdev = to_platform_device(dev);
> +	enum usb_device_speed speed = usb_get_maximum_speed(dev);
> +	bool usb2only = false;
> +	void __iomem *glue;
> +
> +	/* Wireless USB is not supported */
> +	if (speed == USB_SPEED_WIRELESS)
> +		return dev_err_probe(dev, -EINVAL, "Wireless USB not supported\n");
> +
> +	/* No USB 3 PHY in DT means this is surely USB 2 controller */
> +	if (device_property_match_string(dev, "phy-names", "usb3-phy") < 0)
> +		usb2only = true;
> +
> +	if (speed <= USB_SPEED_HIGH)
> +		usb2only = true;

[Severity: High]
Will this condition inadvertently force the controller into USB 2.0 mode when
the maximum-speed property is missing from the device tree?

When the maximum-speed property is absent, usb_get_maximum_speed() returns
USB_SPEED_UNKNOWN, which evaluates to 0. Since 0 is less than USB_SPEED_HIGH,
this condition evaluates to true and unconditionally sets usb2only to true.

This appears to override the preceding logic that correctly checked the
phy-names property to detect USB 3 capabilities. Could this cause hardware
with a USB 3 PHY to be improperly downgraded to USB 2.0 mode?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260828182415.388367-1-marek.vasut+renesas@mailbox.org?part=2