linux-kernel - Re: [PATCH V2 2/8] usb: gadget: tegra-xudc: Add vbus

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Message-ID: <20200428095956.GB3592148@ulmo>
Date:   Tue, 28 Apr 2020 11:59:56 +0200
From:   Thierry Reding <thierry.reding@...il.com>
To:     Nagarjuna Kristam <nkristam@...dia.com>
Cc:     balbi@...nel.org, gregkh@...uxfoundation.org, jonathanh@...dia.com,
        mark.rutland@....com, robh+dt@...nel.org, kishon@...com,
        devicetree@...r.kernel.org, linux-tegra@...r.kernel.org,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V2 2/8] usb: gadget: tegra-xudc: Add vbus_draw support

On Wed, Apr 15, 2020 at 01:55:02PM +0530, Nagarjuna Kristam wrote:
> Register vbus_draw to gadget ops and update corresponding vbus
> draw current to usb_phy.
> 
> Signed-off-by: Nagarjuna Kristam <nkristam@...dia.com>
> ---
> V2:
>  - Patch re-based.
> ---
>  drivers/usb/gadget/udc/tegra-xudc.c | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
> 
> diff --git a/drivers/usb/gadget/udc/tegra-xudc.c b/drivers/usb/gadget/udc/tegra-xudc.c
> index 52a6add..9d3c109 100644
> --- a/drivers/usb/gadget/udc/tegra-xudc.c
> +++ b/drivers/usb/gadget/udc/tegra-xudc.c
> @@ -492,6 +492,7 @@ struct tegra_xudc {
>  	bool powergated;
>  
>  	struct usb_phy **usbphy;
> +	struct usb_phy *curr_usbphy;
>  	struct notifier_block vbus_nb;
>  
>  	struct completion disconnect_complete;
> @@ -719,6 +720,7 @@ static int tegra_xudc_vbus_notify(struct notifier_block *nb,
>  	if (!xudc->suspended && phy_index != -1) {
>  		xudc->curr_utmi_phy = xudc->utmi_phy[phy_index];
>  		xudc->curr_usb3_phy = xudc->usb3_phy[phy_index];
> +		xudc->curr_usbphy = usbphy;
>  		schedule_work(&xudc->usb_role_sw_work);
>  	}
>  
> @@ -2042,6 +2044,19 @@ static int tegra_xudc_gadget_stop(struct usb_gadget *gadget)
>  	return 0;
>  }
>  
> +static int tegra_xudc_gadget_vbus_draw(struct usb_gadget *gadget,
> +						unsigned int m_a)
> +{
> +	struct tegra_xudc *xudc = to_xudc(gadget);
> +
> +	dev_dbg(xudc->dev, "%s: %u mA\n", __func__, m_a);
> +
> +	if (xudc->curr_usbphy->chg_type == SDP_TYPE)
> +		usb_phy_set_power(xudc->curr_usbphy, m_a);

Do we need to propagate the error code here in case the USB PHY for some
reason doesn't support the given current? Or is it guaranteed that we
always do support whatever is passed in here?

Regardless of whether we support it or not, it might still be useful to
add proper handling, if for nothing else but to set a good example.

Thierry

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