Re: [RFC][PATCH 3/3] usb: dwc3: Registering a role switch in the DRD code.

From: Roger Quadros <rogerq@ti.com>
To: John Stultz <john.stultz@linaro.org>, Felipe Balbi <balbi@kernel.org>
Cc: lkml <linux-kernel@vger.kernel.org>,
	Yu Chen <chenyu56@huawei.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Rob Herring <robh+dt@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Heikki Krogerus <heikki.krogerus@linux.intel.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	Chunfeng Yun <chunfeng.yun@mediatek.com>,
	Hans de Goede <hdegoede@redhat.com>,
	Andy Shevchenko <andy.shevchenko@gmail.com>,
	Jun Li <lijun.kernel@gmail.com>,
	Valentin Schneider <valentin.schneider@arm.com>,
	Linux USB List <linux-usb@vger.kernel.org>,
	"open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
	<devicetree@vger.kernel.org>
Subject: Re: [RFC][PATCH 3/3] usb: dwc3: Registering a role switch in the DRD code.
Date: Wed, 16 Oct 2019 12:24:55 +0300	[thread overview]
Message-ID: <fc74130f-bc8e-5d44-2c4a-340934c7b1d3@ti.com> (raw)
In-Reply-To: <CALAqxLUVd5Eo_9tuP9aQUpNT0gnewBv8Dpvsj8UT3MucmzCJVQ@mail.gmail.com>

On 15/10/2019 22:10, John Stultz wrote:
> On Tue, Oct 15, 2019 at 1:25 AM Roger Quadros <rogerq@ti.com> wrote:
>> On 03/10/2019 02:16, John Stultz wrote:
>>> @@ -487,7 +539,28 @@ int dwc3_drd_init(struct dwc3 *dwc)
>>>        if (IS_ERR(dwc->edev))
>>>                return PTR_ERR(dwc->edev);
>>>
>>> -     if (dwc->edev) {
>>> +     if (device_property_read_bool(dwc->dev, "usb-role-switch")) {
>>
>> I think we should use role switch unconditionally and get rid of the
>> debugfs role status/change mechanism.
>>
>>> +             struct usb_role_switch_desc dwc3_role_switch = {0};
>>> +             u32 mode;
>>> +
>>> +             if (device_property_read_bool(dwc->dev,
>>> +                                           "role-switch-default-host")) {
>>> +                     dwc->role_switch_default_mode = USB_DR_MODE_HOST;
>>> +                     mode = DWC3_GCTL_PRTCAP_HOST;
>>> +             } else {
>>> +                     dwc->role_switch_default_mode = USB_DR_MODE_PERIPHERAL;
>>> +                     mode = DWC3_GCTL_PRTCAP_DEVICE;
>>> +             }
>>> +             dwc3_role_switch.fwnode = dev_fwnode(dwc->dev);
>>> +             dwc3_role_switch.set = dwc3_usb_role_switch_set;
>>> +             dwc3_role_switch.get = dwc3_usb_role_switch_get;
>>> +             dwc->role_sw = usb_role_switch_register(dwc->dev,
>>> +                                                     &dwc3_role_switch);
>>> +             if (IS_ERR(dwc->role_sw))
>>> +                     return PTR_ERR(dwc->role_sw);
>>> +
>>> +             dwc3_set_mode(dwc, mode);
>>> +     } else if (dwc->edev) {
>>
>> Role switch should exist regardless if dwc->edev is present or not.
> 
> Does that risk duplicative mode sets when things change (via the
> dwc3_drd_notifier and dwc3_usb_role_switch_set calls?).

Yes, we need to deal with it in the driver. e.g. in current case
when debugfs overrides a role from "otg" to "host" or "device",
we ignore the notifier.

Something similar could be done with role switch I think.

Felipe, what do you think?

-- 
cheers,
-roger
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