linux-kernel - Re: [PATCH v4 1/9] usb: dwc3: add dual-role support

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Date:	Mon, 7 Sep 2015 12:39:05 +0300
From:	Roger Quadros <rogerq@...com>
To:	Peter Chen <peter.chen@...escale.com>
CC:	<balbi@...com>, <tony@...mide.com>, <Joao.Pinto@...opsys.com>,
	<sergei.shtylyov@...entembedded.com>, <jun.li@...escale.com>,
	<linux-usb@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<linux-omap@...r.kernel.org>
Subject: Re: [PATCH v4 1/9] usb: dwc3: add dual-role support

Peter,

On 06/09/15 05:02, Peter Chen wrote:
> On Wed, Sep 02, 2015 at 05:24:16PM +0300, Roger Quadros wrote:
>> Register with the USB OTG core. Since we don't support
>> OTG yet we just work as a dual-role device even
>> if device tree says "otg".
>>
>> +
>> +static int dwc3_drd_init(struct dwc3 *dwc)
>> +{
>> +	int ret, id, vbus;
>> +	struct usb_otg_caps *otgcaps = &dwc->otg_config.otg_caps;
>> +
>> +	otgcaps->otg_rev = 0;
>> +	otgcaps->hnp_support = false;
>> +	otgcaps->srp_support = false;
>> +	otgcaps->adp_support = false;
>> +	dwc->otg_config.fsm_ops = &dwc3_drd_ops;
>> +
>> +	if (!dwc->edev) {
>> +		dev_err(dwc->dev, "No extcon device found for OTG mode\n");
>> +		return -ENODEV;
>> +	}
>> +
> 
> Do All dwc3 platforms id/vbus need to get through extcon? Do the
> SoCs have id/vbus pin?
> 
> 

Extcon access is in fact not needed from dwc3 driver and I will be getting
rid of this patch. We will support dual-role only via the OTG irq as in patch 5.

The way it works is that the OMAP glue layer dwc3-omap.c requests extcon device
and sets some mailbox register and this causes the VBUS/ID events to come over
OTG irq/status. So this patch is redundant.

The extcon device is not needed for all TI platforms. e.g. we need it for
DRA7 but not for AM437x.

cheers,
-roger
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