linux-kernel - RE: [PATCH v3] usb: chipidea: Grab the (legacy) USB PHY by phandle first

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Message-ID: <VI1PR04MB53274C03CD18C3D3ADB767408B630@VI1PR04MB5327.eurprd04.prod.outlook.com>
Date:   Mon, 18 Feb 2019 03:04:17 +0000
From:   Peter Chen <peter.chen@....com>
To:     Paul Kocialkowski <paul.kocialkowski@...tlin.com>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>
Subject: RE: [PATCH v3] usb: chipidea: Grab the (legacy) USB PHY by phandle
 first

 
> According to the chipidea driver bindings, the USB PHY is specified via the "phys"
> phandle node. However, this only takes effect for USB PHYs that use the common
> PHY framework. For legacy USB PHYs, a simple lookup based on the USB PHY
> type is done instead.
> 
> This does not play out well when more than one USB PHY is registered, since the
> first registered PHY matching the type will always be returned regardless of what
> the driver was bound to.
> 
> Fix this by looking up the PHY based on the "phys" phandle node.
> Although generic PHYs are rather matched by their "phys-name" and not the "phys"
> phandle directly, there is no helper for similar lookup on legacy PHYs and it's
> probably not worth the effort to add it.
> 
> When no legacy USB PHY is found by phandle, fallback to grabbing any registered
> USB2 PHY. This ensures backward compatibility if some users were actually relying
> on this mechanism.
> 
> Signed-off-by: Paul Kocialkowski <paul.kocialkowski@...tlin.com>
> ---
> Changes since v2:
> * Fixed typos in commit message.
> 
> Changes since v1:
> * Only consider legacy USB PHY error for fallback as suggested;
> * Checked against EPROBE_DEFER before entering fallback.
> 
>  drivers/usb/chipidea/core.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/usb/chipidea/core.c b/drivers/usb/chipidea/core.c index
> 7bfcbb23c2a4..016e4004fe9d 100644
> --- a/drivers/usb/chipidea/core.c
> +++ b/drivers/usb/chipidea/core.c
> @@ -954,8 +954,15 @@ static int ci_hdrc_probe(struct platform_device *pdev)
>  	} else if (ci->platdata->usb_phy) {
>  		ci->usb_phy = ci->platdata->usb_phy;
>  	} else {
> +		ci->usb_phy = devm_usb_get_phy_by_phandle(dev->parent, "phys",
> +							  0);
>  		ci->phy = devm_phy_get(dev->parent, "usb-phy");
> -		ci->usb_phy = devm_usb_get_phy(dev->parent,
> USB_PHY_TYPE_USB2);
> +
> +		/* Fallback to grabbing any registered USB2 PHY */
> +		if (IS_ERR(ci->usb_phy) &&
> +		    PTR_ERR(ci->usb_phy) != -EPROBE_DEFER)
> +			ci->usb_phy = devm_usb_get_phy(dev->parent,
> +						       USB_PHY_TYPE_USB2);
> 

I think you may need to do above if ci->phy is error, and not the error is -EPROBE_DEFER.

Peter

>  		/* if both generic PHY and USB PHY layers aren't enabled */
>  		if (PTR_ERR(ci->phy) == -ENOSYS &&
> --
> 2.20.1