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From: John Stultz <john.stultz@linaro.org>
Newsgroups: linux.kernel
Subject: Re: [RFC][PATCH 2/5] usb: dwc2: Workaround case where GOTGCTL state  is wrong
Date: Tue, 13 Dec 2016 22:20:01 +0100
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On Tue, Dec 13, 2016 at 4:28 AM, Vardan Mikayelyan
<Vardan.Mikayelyan@synopsys.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@hisilicon.com>
>> Cc: Guodong Xu <guodong.xu@linaro.org>
>> Cc: Amit Pundir <amit.pundir@linaro.org>
>> Cc: Rob Herring <robh+dt@kernel.org>
>> Cc: John Youn <johnyoun@synopsys.com>
>> Cc: Douglas Anderson <dianders@chromium.org>
>> Cc: Chen Yu <chenyu56@huawei.com>
>> Cc: Kishon Vijay Abraham I <kishon@ti.com>
>> Cc: Felipe Balbi <felipe.balbi@linux.intel.com>
>> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>> Cc: linux-usb@vger.kernel.org
>> Acked-by: John Youn <johnyoun@synopsys.com>
>> Signed-off-by: John Stultz <john.stultz@linaro.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@synopsys.com>"

Thanks so much for your review!
-john