linux-kernel - Re: [PATCH v3] usb: dwc3: Add support for VBUS power control

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Date:   Thu, 23 Jul 2020 09:56:14 +0200
From:   Vincent Whitchurch <vincent.whitchurch@...s.com>
To:     Mike Looijmans <mike.looijmans@...ic.nl>
CC:     <linux-usb@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <balbi@...nel.org>, <gregkh@...uxfoundation.org>,
        <lgirdwood@...il.com>, <broonie@...nel.org>
Subject: Re: [PATCH v3] usb: dwc3: Add support for VBUS power control

On Fri, Jun 19, 2020 at 04:25:12PM +0200, Mike Looijmans wrote:
> +void dwc3_set_vbus(struct dwc3 *dwc, bool enable)
> +{
> +	int ret;
> +
> +	if (enable != dwc->vbus_reg_enabled) {
> +		if (enable)
> +			ret = regulator_enable(dwc->vbus_reg);
> +		else
> +			ret = regulator_disable(dwc->vbus_reg);

dwc->vbus_reg is set to NULL when the regulator is not present.  These
regulator_* functions expect a non-NULL pointer so a NULL check is
required before calling them.

> +		if (!ret)
> +			dwc->vbus_reg_enabled = enable;
> +	}
> +
> +	if (dwc->usb2_phy)
> +		otg_set_vbus(dwc->usb2_phy->otg, enable);
> +}
> +
>  static void __dwc3_set_mode(struct work_struct *work)
>  {
>  	struct dwc3 *dwc = work_to_dwc(work);
> @@ -164,8 +182,7 @@ static void __dwc3_set_mode(struct work_struct *work)
>  		if (ret) {
>  			dev_err(dwc->dev, "failed to initialize host\n");
>  		} else {
> -			if (dwc->usb2_phy)
> -				otg_set_vbus(dwc->usb2_phy->otg, true);
> +			dwc3_set_vbus(dwc, true);
>  			phy_set_mode(dwc->usb2_generic_phy, PHY_MODE_USB_HOST);
>  			phy_set_mode(dwc->usb3_generic_phy, PHY_MODE_USB_HOST);
>  		}
> @@ -173,8 +190,7 @@ static void __dwc3_set_mode(struct work_struct *work)
>  	case DWC3_GCTL_PRTCAP_DEVICE:
>  		dwc3_event_buffers_setup(dwc);
>  
> -		if (dwc->usb2_phy)
> -			otg_set_vbus(dwc->usb2_phy->otg, false);
> +		dwc3_set_vbus(dwc, false);
>  		phy_set_mode(dwc->usb2_generic_phy, PHY_MODE_USB_DEVICE);
>  		phy_set_mode(dwc->usb3_generic_phy, PHY_MODE_USB_DEVICE);
>  
> @@ -1183,8 +1199,7 @@ static int dwc3_core_init_mode(struct dwc3 *dwc)
>  	case USB_DR_MODE_PERIPHERAL:
>  		dwc3_set_prtcap(dwc, DWC3_GCTL_PRTCAP_DEVICE);
>  
> -		if (dwc->usb2_phy)
> -			otg_set_vbus(dwc->usb2_phy->otg, false);
> +		dwc3_set_vbus(dwc, false);
>  		phy_set_mode(dwc->usb2_generic_phy, PHY_MODE_USB_DEVICE);
>  		phy_set_mode(dwc->usb3_generic_phy, PHY_MODE_USB_DEVICE);
>  
> @@ -1198,8 +1213,7 @@ static int dwc3_core_init_mode(struct dwc3 *dwc)
>  	case USB_DR_MODE_HOST:
>  		dwc3_set_prtcap(dwc, DWC3_GCTL_PRTCAP_HOST);
>  
> -		if (dwc->usb2_phy)
> -			otg_set_vbus(dwc->usb2_phy->otg, true);
> +		dwc3_set_vbus(dwc, true);
>  		phy_set_mode(dwc->usb2_generic_phy, PHY_MODE_USB_HOST);
>  		phy_set_mode(dwc->usb3_generic_phy, PHY_MODE_USB_HOST);
>  
> @@ -1470,6 +1484,14 @@ static int dwc3_probe(struct platform_device *pdev)
>  
>  	dwc3_get_properties(dwc);
>  
> +	dwc->vbus_reg = devm_regulator_get_optional(dev, "vbus");
> +	if (IS_ERR(dwc->vbus_reg)) {
> +		if (PTR_ERR(dwc->vbus_reg) == -EPROBE_DEFER)
> +			return -EPROBE_DEFER;

Some drivers seem to do it this way, but I think it would be more
correct to return all errors that aren't ENODEV, like
drivers/gpu/drm/exynos/exynos_hdmi.c does.  That way you would allow the
regulator to not be present, but you also wouldn't silently ignore other
errors such as ENOMEM.

> +
> +		dwc->vbus_reg = NULL;
> +	}
> +