MIME-Version: 1.0
In-Reply-To: <5c4f7288-c0b1-f770-2141-067f4724e95f@synopsys.com>
References: <1481011582-7162-1-git-send-email-john.stultz@linaro.org>
 <1481011582-7162-2-git-send-email-john.stultz@linaro.org> <4be239ba-b2f1-a951-d558-7469bf835556@synopsys.com>
 <CALAqxLVtGugr9Uw3d3G6NZW0LQ5+t54yV8wkNALnUTwBp9+-2A@mail.gmail.com> <5c4f7288-c0b1-f770-2141-067f4724e95f@synopsys.com>
From: John Stultz <john.stultz@linaro.org>
Date: Tue, 6 Dec 2016 16:35:06 -0800
Message-ID: <CALAqxLU+53bpcKtKtVKHRMC4fc8zrXfp9xObGaUNWJyixPLORw@mail.gmail.com>
Subject: Re: [RFC][PATCH 1/3 v2] usb: dwc2: Add extcon support to dwc2 driver
To: John Youn <John.Youn@synopsys.com>
Cc: lkml <linux-kernel@vger.kernel.org>, Wei Xu <xuwei5@hisilicon.com>,
        Guodong Xu <guodong.xu@linaro.org>,
        Amit Pundir <amit.pundir@linaro.org>, Rob Herring <robh+dt@kernel.org>,
        Douglas Anderson <dianders@chromium.org>,
        Chen Yu <chenyu56@huawei.com>, Kishon Vijay Abraham I <kishon@ti.com>,
        Felipe Balbi <felipe.balbi@linux.intel.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        "linux-usb@vger.kernel.org" <linux-usb@vger.kernel.org>
Content-Type: text/plain; charset=UTF-8
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1816
Lines: 40

On Tue, Dec 6, 2016 at 4:26 PM, John Youn <John.Youn@synopsys.com> wrote:
> On 12/6/2016 4:05 PM, John Stultz wrote:
>> On Tue, Dec 6, 2016 at 3:17 PM, John Youn <John.Youn@synopsys.com> wrote:
>>> Also, do you really need this at all? Wasn't your system previously
>>> able to detect the ID pin change correctly via the connection id
>>> status change interrupt? This would only be needed if that were not
>>> the case.
>>
>> So it can be made work w/o this, but we needed other hacks because the
>> usb-gadget disconnect logic never triggered when the cable was
>> unplugged. The controller would jump over to host mode, then when we
>> re-plugged in the usb-gadget cable, it would fail often as we never
>> got a disconnect signal.  That's why earlier I was using this hack to
>> force gadget disconnect before the reset was called:
>> https://lkml.org/lkml/2016/10/20/26
>
> Other than the triggering WARN_ON() in fifo init, is there any other
> negative effects?

Well, when we see the WARN_ON, it doesn't connect into usb-gadget
mode. I had to unplug and re-plug the cable.
(The hack I linked to above avoids this, but I suspect its not correct).

Also Amit Pundir had mentioned earlier that the UDC sysfs state
doesn't get reported correctly since it doesn't register the
usb-gadget as unplugged until the cable is re-inserted.

> We are revisiting this fifo init code and I think the fifo init is not
> necessary for USB_RESET purposes. This should get rid of a race
> condition where the EP's are not disabled before attempting to
> initialize their FIFO's. Which should get rid of the WARN_ON().
>
> If this is the only issue, then this will probably resolve it.

(Basically that and the two suspend fixes I sent along in this patchset :).

I'd be happy to test anything you're playing with.

thanks
-john