linux-kernel - Re: [PATCH] usb: dwc3: Properly handle processing of pending events

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Date:   Wed, 2 Aug 2023 17:37:08 +0300
From:   Roger Quadros <rogerq@...nel.org>
To:     庞苏荣 (Surong Pang) 
        <surong.pang@...soc.com>, Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
        Elson Roy Serrao <quic_eserrao@...cinc.com>
Cc:     "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "felipe.balbi@...ux.intel.com" <felipe.balbi@...ux.intel.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "quic_wcheng@...cinc.com" <quic_wcheng@...cinc.com>,
        "quic_jackp@...cinc.com" <quic_jackp@...cinc.com>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: Re: [PATCH] usb: dwc3: Properly handle processing of pending events

Hi,

On 02/08/2023 04:39, 庞苏荣 (Surong Pang) wrote:
> Dears，
> If there is/are event(s) in evt->buf,  in dwc3_check_event_buf,  dwc3_thread_interrupt will be woke up.

How will it be woken up if we had disabled the IRQ to begin with?

> 
>>> @@ -4718,6 +4723,8 @@ void dwc3_gadget_process_pending_events(struct
>>> dwc3 *dwc)  {
>>>       if (dwc->pending_events) {
>>>               dwc3_interrupt(dwc->irq_gadget, dwc->ev_buf);
>>> +             dwc3_thread_interrupt(dwc->irq_gadget, dwc->ev_buf);
>>> +             pm_runtime_put(dwc->dev);
>>>               dwc->pending_events = false;
>>>               enable_irq(dwc->irq_gadget);
>>>       }
> 
> I just want to know dwc3_thread_interrupt here is necessary or not?
> 
As IRQ was disabled, we will have to call dwc3_thread_interrupt() to
process the events that are still pending.

> 
>> On Tue, Aug 02, 2023 8:12 Thinh Nguyen wrote:
>>> On Tue, Aug 01, 2023, Elson Roy Serrao wrote:
>>> If dwc3 is runtime suspended we defer processing the event buffer
>>> until resume, by setting the pending_events flag. Set this flag before
>>> triggering resume to avoid race with the runtime resume callback.
>>>
>>> While handling the pending events, in addition to checking the event
>>> buffer we also need to process it. Handle this by explicitly calling
>>> dwc3_thread_interrupt(). Also balance the runtime pm get() operation
>>> that triggered this processing.
>>>
>>> Cc: stable@...r.kernel.org
>>> Fixes: fc8bb91bc83e ("usb: dwc3: implement runtime PM")
>>> Signed-off-by: Elson Roy Serrao <quic_eserrao@...cinc.com>
>>> ---
>>> Change separated from below series as an independent fix based on the
>>> earlier discussion
>>> https://urldefense.com/v3/__https://lore.kernel.org/all/be57511d-2005-
>>> a1f5-d5a5-809e71029aec@...cinc.com/__;!!A4F2R9G_pg!YtZ93ALEpDNTCEhf0WE
>>> yB5S090pPlKIKVtjqTOAEJdxdWbl8QG6eiRmlvfivUtD5qjKWWLX2C4fb4W8VAg5w9qasL
>>> uKB$
>>>
>>>  drivers/usb/dwc3/gadget.c | 9 ++++++++-
>>>  1 file changed, 8 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
>>> index 5fd067151fbf..858fe4c299b7 100644
>>> --- a/drivers/usb/dwc3/gadget.c
>>> +++ b/drivers/usb/dwc3/gadget.c
>>> @@ -4455,9 +4455,14 @@ static irqreturn_t dwc3_check_event_buf(struct dwc3_event_buffer *evt)
>>>       u32 count;
>>>
>>>       if (pm_runtime_suspended(dwc->dev)) {
>>> +             dwc->pending_events = true;
>>> +             /*
>>> +              * Trigger runtime resume. The get() function will be balanced
>>> +              * after processing the pending events in dwc3_process_pending
>>> +              * events().
>>> +              */
>>>               pm_runtime_get(dwc->dev);
>>>               disable_irq_nosync(dwc->irq_gadget);
>>> -             dwc->pending_events = true;
>>>               return IRQ_HANDLED;
>>>       }
>>>
>>> @@ -4718,6 +4723,8 @@ void dwc3_gadget_process_pending_events(struct
>>> dwc3 *dwc)  {
>>>       if (dwc->pending_events) {
>>>               dwc3_interrupt(dwc->irq_gadget, dwc->ev_buf);
>>> +             dwc3_thread_interrupt(dwc->irq_gadget, dwc->ev_buf);
>>> +             pm_runtime_put(dwc->dev);
>>>               dwc->pending_events = false;
>>>               enable_irq(dwc->irq_gadget);
>>>       }
>>> --
>>> 2.17.1
>>>
>>
>> This fix is more complete.
>>
>> Acked-by: Thinh Nguyen <Thinh.Nguyen@...opsys.com>
>>
>> Thanks,
>> Thinh

-- 
cheers,
-roger