linux-kernel - Re: [RFC][PATCH 2/5] usb: dwc2: Workaround case where GOTGCTL state is wrong

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Date:   Tue, 13 Dec 2016 12:28:15 +0000
From:   Vardan Mikayelyan <Vardan.Mikayelyan@...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>,
        Kishon Vijay Abraham I <kishon@...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 2/5] usb: dwc2: Workaround case where GOTGCTL state
 is wrong

On 12/13/2016 11:12 AM, John Stultz wrote:
> When removing a USB-A to USB-otg adapter cable, we get a change
> status irq, and then in dwc2_conn_id_status_change, we
> erroniously see the GOTGCTL_CONID_B flag set. This causes us to
> get  stuck in the "while (!dwc2_is_device_mode(hsotg))" loop,
> spitting out "Waiting for Peripheral Mode, Mode=Host" warnings
> until it fails out many seconds later.
>
> This patch works around the issue by re-reading the GOTGCTL
> state to check if the GOTGCTL_CONID_B is still set and if not
> restarting the change status logic.
>
> I suspect this isn't the best solution, but it seems to work
> well for me.
>
> Feedback would be greatly appreciated!
>
> 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: Kishon Vijay Abraham I <kishon@...com>
> Cc: Felipe Balbi <felipe.balbi@...ux.intel.com>
> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Cc: linux-usb@...r.kernel.org
> Acked-by: John Youn <johnyoun@...opsys.com>
> Signed-off-by: John Stultz <john.stultz@...aro.org>
> ---
>  drivers/usb/dwc2/hcd.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/usb/dwc2/hcd.c b/drivers/usb/dwc2/hcd.c
> index df5a065..a3f34dd 100644
> --- a/drivers/usb/dwc2/hcd.c
> +++ b/drivers/usb/dwc2/hcd.c
> @@ -3199,7 +3199,7 @@ static void dwc2_conn_id_status_change(struct work_struct *work)
>  	dev_dbg(hsotg->dev, "gotgctl=%0x\n", gotgctl);
>  	dev_dbg(hsotg->dev, "gotgctl.b.conidsts=%d\n",
>  		!!(gotgctl & GOTGCTL_CONID_B));
> -
> +again:
>  	/* B-Device connector (Device Mode) */
>  	if (gotgctl & GOTGCTL_CONID_B) {
>  		/* Wait for switch to device mode */
> @@ -3210,6 +3210,9 @@ static void dwc2_conn_id_status_change(struct work_struct *work)
>  				 dwc2_is_host_mode(hsotg) ? "Host" :
>  				 "Peripheral");
>  			usleep_range(20000, 40000);
> +			gotgctl = dwc2_readl(hsotg->regs + GOTGCTL);
> +			if (!(gotgctl & GOTGCTL_CONID_B))
> +				goto again;
>  			if (++count > 250)
>  				break;
>  		}
>
Hi John Stultz,

When it goes to ":again", it will go to else anyways. I'll suggest 
alternative way to do this. Please see below.

Also you can add "Reviewed-by: Vardan Mikayelyan <mvardan@...opsys.com>"

Thanks,
Vardan.

diff --git a/drivers/usb/dwc2/hcd.c b/drivers/usb/dwc2/hcd.c
index b7311a6..128311b 100644
--- a/drivers/usb/dwc2/hcd.c
+++ b/drivers/usb/dwc2/hcd.c
@@ -3242,6 +3242,9 @@ static void dwc2_conn_id_status_change(struct 
work_struct *work)
                                  dwc2_is_host_mode(hsotg) ? "Host" :
                                  "Peripheral");
                         usleep_range(20000, 40000);
+                       gotgctl = dwc2_readl(hsotg->regs + GOTGCTL);
+                       if (!(gotgctl & GOTGCTL_CONID_B))
+                               goto host;
                         if (++count > 250)
                                 break;
                 }
@@ -3256,6 +3259,7 @@ static void dwc2_conn_id_status_change(struct 
work_struct *work)
                 spin_unlock_irqrestore(&hsotg->lock, flags);
                 dwc2_hsotg_core_connect(hsotg);
         } else {
+host:
                 /* A-Device connector (Host Mode) */
                 dev_dbg(hsotg->dev, "connId A\n");
                 while (!dwc2_is_host_mode(hsotg)) {