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Subject: Re: [PATCH 1/2] USB: dwc3: get extcon device by OF graph bindings
To:     "open list:DESIGNWARE USB3 DRD IP DRIVER" <linux-usb@vger.kernel.org>
Cc:     Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
        Marek Szyprowski <m.szyprowski@samsung.com>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@vger.kernel.org>, Felipe Balbi <balbi@kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Inki Dae <inki.dae@samsung.com>,
        Rob Herring <robh+dt@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Krzysztof Kozlowski <krzk@kernel.org>,
        Chanwoo Choi <cw00.choi@samsung.com>,
        Laurent Pinchart <Laurent.pinchart@ideasonboard.com>,
        linux-kernel@vger.kernel.org, linux-samsung-soc@vger.kernel.org
From:   Andrzej Hajda <a.hajda@samsung.com>
Message-ID: <1080506a-adaa-193b-24d5-a779486dacc8@samsung.com>
Date:   Mon, 14 May 2018 10:38:55 +0200
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On 31.01.2018 16:57, Andrzej Hajda wrote:
> extcon device is used to detect host/device connection. Since extcon
> OF property is deprecated, alternative method should be added.
> This method uses OF graph bindings to locate extcon.
>
> Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>

Ping, 3.5 months passed.

Regards
Andrzej

> ---
> Hi all,
>
> This patch implements alternative method to get extcon from DWC3.
> The code works but is hacky, as DWC3 must traverse different DT nodes
> to get extcon, in case of TM2 it is USB-PHY and MUIC, but other
> platforms can have different paths.
> I would be glad if it can be merged as is for now, but additional work
> must be done to make it generic.
> I guess on DT binding side it is OK. So the problem should be addressed
> in the code.
> My rough idea is to implement kind of extcon aliases/forwarder mechanism,
> ie. USB-PHY will expect on its output remote port extcon, and it should register
> extcon-forwarder pointing to this extcon. This way DWC3 can look for the extcon
> on its PHY phandle, and it will receive via forwarding mechanism extcon
> exposed by MUIC.
> As I said this is rough idea for discussion, other propositions are welcome.
>
> Regards
> Andrzej
> ---
>  drivers/usb/dwc3/drd.c | 41 ++++++++++++++++++++++++++++-------------
>  1 file changed, 28 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/usb/dwc3/drd.c b/drivers/usb/dwc3/drd.c
> index cc8ab9a8e9d2..eee2eca3d513 100644
> --- a/drivers/usb/dwc3/drd.c
> +++ b/drivers/usb/dwc3/drd.c
> @@ -8,6 +8,7 @@
>   */
>  
>  #include <linux/extcon.h>
> +#include <linux/of_graph.h>
>  
>  #include "debug.h"
>  #include "core.h"
> @@ -38,24 +39,38 @@ static int dwc3_drd_notifier(struct notifier_block *nb,
>  	return NOTIFY_DONE;
>  }
>  
> +struct extcon_dev *dwc3_get_extcon(struct dwc3 *dwc)
> +{
> +	struct device *dev = dwc->dev;
> +	struct device_node *np_phy, *np_conn;
> +	struct extcon_dev *edev;
> +
> +	if (of_property_read_bool(dev->of_node, "extcon"))
> +		return extcon_get_edev_by_phandle(dwc->dev, 0);
> +
> +	np_phy = of_parse_phandle(dev->of_node, "phys", 0);
> +	np_conn = of_graph_get_remote_node(np_phy, -1, -1);
> +	edev = extcon_get_edev_by_of_node(np_conn);
> +	of_node_put(np_conn);
> +	of_node_put(np_phy);
> +
> +	return edev;
> +}
> +
>  int dwc3_drd_init(struct dwc3 *dwc)
>  {
>  	int ret;
>  
> -	if (dwc->dev->of_node) {
> -		if (of_property_read_bool(dwc->dev->of_node, "extcon"))
> -			dwc->edev = extcon_get_edev_by_phandle(dwc->dev, 0);
> -
> -		if (IS_ERR(dwc->edev))
> -			return PTR_ERR(dwc->edev);
> +	dwc->edev = dwc3_get_extcon(dwc);
> +	if (IS_ERR(dwc->edev))
> +		return PTR_ERR(dwc->edev);
>  
> -		dwc->edev_nb.notifier_call = dwc3_drd_notifier;
> -		ret = extcon_register_notifier(dwc->edev, EXTCON_USB_HOST,
> -					       &dwc->edev_nb);
> -		if (ret < 0) {
> -			dev_err(dwc->dev, "couldn't register cable notifier\n");
> -			return ret;
> -		}
> +	dwc->edev_nb.notifier_call = dwc3_drd_notifier;
> +	ret = extcon_register_notifier(dwc->edev, EXTCON_USB_HOST,
> +				       &dwc->edev_nb);
> +	if (ret < 0) {
> +		dev_err(dwc->dev, "couldn't register cable notifier\n");
> +		return ret;
>  	}
>  
>  	dwc3_drd_update(dwc);