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

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Message-ID: <CALAqxLV3uEzjM1Ljwv+=_NRL5XVb5syQ7Ehbq7u5ecPObBsqhQ@mail.gmail.com>
Date:   Tue, 13 Dec 2016 12:40:15 -0800
From:   John Stultz <john.stultz@...aro.org>
To:     Vardan Mikayelyan <Vardan.Mikayelyan@...opsys.com>
Cc:     lkml <linux-kernel@...r.kernel.org>, 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 Tue, Dec 13, 2016 at 4:28 AM, Vardan Mikayelyan
<Vardan.Mikayelyan@...opsys.com> wrote:
> 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.

Sounds good. I've made the change.

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

Thanks so much for your review!
-john