Re: [PATCH] usb: dwc3: Remove WARN_ON for device endpoint command timeouts

[Selvarasu Ganesan <selvarasu.g@samsung.com>]

On 8/6/2025 5:08 AM, Thinh Nguyen wrote:
> On Mon, Aug 04, 2025, Selvarasu Ganesan wrote:
>> From: Akash M <akash.m5@samsung.com>
>>
>> This commit addresses a rarely observed endpoint command timeout
>> which causes kernel panic due to warn when 'panic_on_warn' is enabled
>> and unnecessary call trace prints when 'panic_on_warn' is disabled.
>> It is seen during fast software-controlled connect/disconnect testcases.
>> The following is one such endpoint command timeout that we observed:
>>
>> 1. Connect
>>     =======
>> ->dwc3_thread_interrupt
>>   ->dwc3_ep0_interrupt
>>    ->configfs_composite_setup
>>     ->composite_setup
>>      ->usb_ep_queue
>>       ->dwc3_gadget_ep0_queue
>>        ->__dwc3_gadget_ep0_queue
>>         ->__dwc3_ep0_do_control_data
>>          ->dwc3_send_gadget_ep_cmd
>>
>> 2. Disconnect
>>     ==========
>> ->dwc3_thread_interrupt
>>   ->dwc3_gadget_disconnect_interrupt
>>    ->dwc3_ep0_reset_state
>>     ->dwc3_ep0_end_control_data
>>      ->dwc3_send_gadget_ep_cmd
>>
>> In the issue scenario, in Exynos platforms, we observed that control
>> transfers for the previous connect have not yet been completed and end
>> transfer command sent as a part of the disconnect sequence and
>> processing of USB_ENDPOINT_HALT feature request from the host timeout.
>> This maybe an expected scenario since the controller is processing EP
>> commands sent as a part of the previous connect. It maybe better to
>> remove WARN_ON in all places where device endpoint commands are sent to
>> avoid unnecessary kernel panic due to warn.
>>
>> Fixes: e192cc7b5239 ("usb: dwc3: gadget: move cmd_endtransfer to extra function")
>> Fixes: 72246da40f37 ("usb: Introduce DesignWare USB3 DRD Driver")
>> Fixes: c7fcdeb2627c ("usb: dwc3: ep0: simplify EP0 state machine")
>> Fixes: f0f2b2a2db85 ("usb: dwc3: ep0: push ep0state into xfernotready processing")
>> Fixes: 2e3db064855a ("usb: dwc3: ep0: drop XferNotReady(DATA) support")
>> Cc: stable@vger.kernel.org
> I don't think this is a fix patch. You're just replacing WARN* with
> dev_warn* without doing any recovery. Let's remove the Fixes and table
> tag. Also, can we replace dev_warn* with dev_err* because these are
> critical errors that may put the controller in a bad state.
>
> Thanks,
> Thinh


Hi Thinh,

Thanks for your review comments.
Yeah we agree. This is not a fix patch. Sure we will update new patchset 
with replace dev_warn* with dev_err*.

As for dropping the stable tag,  It would be better these changes to be 
applied across all stable kernels, so shall we keep stable tag in place?

Thanks,
Selva
>
>> Signed-off-by: Akash M <akash.m5@samsung.com>
>> Signed-off-by: Selvarasu Ganesan <selvarasu.g@samsung.com>
>> diff --git a/drivers/usb/dwc3/ep0.c b/drivers/usb/dwc3/ep0.c
>> index 666ac432f52d..7b313836f62b 100644
>> --- a/drivers/usb/dwc3/ep0.c
>> +++ b/drivers/usb/dwc3/ep0.c
>> @@ -288,7 +288,9 @@ void dwc3_ep0_out_start(struct dwc3 *dwc)
>>   	dwc3_ep0_prepare_one_trb(dep, dwc->ep0_trb_addr, 8,
>>   			DWC3_TRBCTL_CONTROL_SETUP, false);
>>   	ret = dwc3_ep0_start_trans(dep);
>> -	WARN_ON(ret < 0);
>> +	if (ret < 0)
>> +		dev_warn(dwc->dev, "ep0 out start transfer failed: %d\n", ret);
>> +
>>   	for (i = 2; i < DWC3_ENDPOINTS_NUM; i++) {
>>   		struct dwc3_ep *dwc3_ep;
>>   
>> @@ -1061,7 +1063,9 @@ static void __dwc3_ep0_do_control_data(struct dwc3 *dwc,
>>   		ret = dwc3_ep0_start_trans(dep);
>>   	}
>>   
>> -	WARN_ON(ret < 0);
>> +	if (ret < 0)
>> +		dev_warn(dwc->dev, "ep0 data phase start transfer failed: %d\n",
>> +				ret);
>>   }
>>   
>>   static int dwc3_ep0_start_control_status(struct dwc3_ep *dep)
>> @@ -1078,7 +1082,12 @@ static int dwc3_ep0_start_control_status(struct dwc3_ep *dep)
>>   
>>   static void __dwc3_ep0_do_control_status(struct dwc3 *dwc, struct dwc3_ep *dep)
>>   {
>> -	WARN_ON(dwc3_ep0_start_control_status(dep));
>> +	int	ret;
>> +
>> +	ret = dwc3_ep0_start_control_status(dep);
>> +	if (ret)
>> +		dev_warn(dwc->dev,
>> +			"ep0 status phase start transfer failed: %d\n", ret);
>>   }
>>   
>>   static void dwc3_ep0_do_control_status(struct dwc3 *dwc,
>> @@ -1121,7 +1130,10 @@ void dwc3_ep0_end_control_data(struct dwc3 *dwc, struct dwc3_ep *dep)
>>   	cmd |= DWC3_DEPCMD_PARAM(dep->resource_index);
>>   	memset(&params, 0, sizeof(params));
>>   	ret = dwc3_send_gadget_ep_cmd(dep, cmd, &params);
>> -	WARN_ON_ONCE(ret);
>> +	if (ret)
>> +		dev_warn_ratelimited(dwc->dev,
>> +			"ep0 data phase end transfer failed: %d\n", ret);
>> +
>>   	dep->resource_index = 0;
>>   }
>>   
>> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
>> index 321361288935..50e4f667b2f2 100644
>> --- a/drivers/usb/dwc3/gadget.c
>> +++ b/drivers/usb/dwc3/gadget.c
>> @@ -1774,7 +1774,11 @@ static int __dwc3_stop_active_transfer(struct dwc3_ep *dep, bool force, bool int
>>   		dep->flags |= DWC3_EP_DELAY_STOP;
>>   		return 0;
>>   	}
>> -	WARN_ON_ONCE(ret);
>> +
>> +	if (ret)
>> +		dev_warn_ratelimited(dep->dwc->dev,
>> +				"end transfer failed: ret = %d\n", ret);
>> +
>>   	dep->resource_index = 0;
>>   
>>   	if (!interrupt)
>> @@ -4041,7 +4045,9 @@ static void dwc3_clear_stall_all_ep(struct dwc3 *dwc)
>>   		dep->flags &= ~DWC3_EP_STALL;
>>   
>>   		ret = dwc3_send_clear_stall_ep_cmd(dep);
>> -		WARN_ON_ONCE(ret);
>> +		if (ret)
>> +			dev_warn_ratelimited(dwc->dev,
>> +				"failed to clear STALL on %s\n", dep->name);
>>   	}
>>   }
>>   
>> -- 
>> 2.17.1