linux-kernel - Re: [RFC][PATCH 3/3] usb: dwc2: Make sure we disconnect the gadget state

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Date:   Mon, 21 Nov 2016 19:23:20 -0800
From:   John Youn <John.Youn@...opsys.com>
To:     John Stultz <john.stultz@...aro.org>,
        lkml <linux-kernel@...r.kernel.org>
CC:     Wei Xu <xuwei5@...ilicon.com>, Guodong Xu <guodong.xu@...aro.org>,
        "Amit Pundir" <amit.pundir@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        John Youn <John.Youn@...opsys.com>,
        Douglas Anderson <dianders@...omium.org>,
        Chen Yu <chenyu56@...wei.com>,
        Felipe Balbi <felipe.balbi@...ux.intel.com>,
        "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>
Subject: Re: [RFC][PATCH 3/3] usb: dwc2: Make sure we disconnect the gadget
 state

On 11/15/2016 1:47 PM, John Stultz wrote:
> I had seen some odd behavior with HiKey's usb-gadget interface
> that I finally seemed to have chased down. Basically every other
> time I pluged in the OTG port, the gadget interface would
> properly initialize. The other times, I'd get a big WARN_ON
> in dwc2_hsotg_init_fifo() about the fifo_map not being clear.

Hi,

The fifo_map could end up not being clear when disconnect is never
sent to the UDC framework. That unsets the configuration and the
endpoints get disabled, which clears the FIFO map.

Looks like the problem happens when going from A-device to B-device.

If you come up as an A-Device, the gadget wouldn't have been
configured so it shouldn't warn going A->B.

If you go B->A, you will get a session end detected, which triggers
the udc disconnect. Then A->B should not warn here either.

Can you determine why this doesn't happen on your system? It sounds
like there might be some race condition that we need to identify. If
you can provide logs with DEBUG enabled that would be helpful too.

Regards,
John


> 
> Ends up if we don't disconnect the gadget state, the fifo-map
> doesn't get cleared properly, which causes WARN_ON messages and
> also results in the device not properly being setup as a gadget
> every other time the OTG port is connected.
> 
> So this patch adds a call to dwc2_hsotg_disconnect() in the
> reset path so the state is properly cleared.
> 
> With it, the gadget interface initializes properly on every
> plug in.
> 
> Cc: Wei Xu <xuwei5@...ilicon.com>
> Cc: Guodong Xu <guodong.xu@...aro.org>
> Cc: Amit Pundir <amit.pundir@...aro.org>
> Cc: Rob Herring <robh+dt@...nel.org>
> Cc: John Youn <johnyoun@...opsys.com>
> Cc: Douglas Anderson <dianders@...omium.org>
> Cc: Chen Yu <chenyu56@...wei.com>
> Cc: Felipe Balbi <felipe.balbi@...ux.intel.com>
> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Cc: linux-usb@...r.kernel.org
> Signed-off-by: John Stultz <john.stultz@...aro.org>
> ---
>  drivers/usb/dwc2/hcd.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/usb/dwc2/hcd.c b/drivers/usb/dwc2/hcd.c
> index 8c980fd..d2557b7 100644
> --- a/drivers/usb/dwc2/hcd.c
> +++ b/drivers/usb/dwc2/hcd.c
> @@ -3228,6 +3228,7 @@ static void dwc2_conn_id_status_change(struct work_struct *work)
>  		dwc2_core_init(hsotg, false);
>  		dwc2_enable_global_interrupts(hsotg);
>  		spin_lock_irqsave(&hsotg->lock, flags);
> +		dwc2_hsotg_disconnect(hsotg);
>  		dwc2_hsotg_core_init_disconnected(hsotg, false);
>  		spin_unlock_irqrestore(&hsotg->lock, flags);
>  		dwc2_hsotg_core_connect(hsotg);
>