Re: [PATCH] usb: dwc3: Clear DWC3_EVENT_PENDING when count is 0

[Linyu Yuan <quic_linyyuan@quicinc.com>]

On 1/5/2023 5:54 PM, 정재훈 wrote:
>
>> -----Original Message-----
>> From: Linyu Yuan [mailto:quic_linyyuan@quicinc.com]
>> Sent: Thursday, January 5, 2023 12:35 PM
>> To: JaeHun Jung; Felipe Balbi; Greg Kroah-Hartman; Thinh Nguyen
>> Cc: open list:USB XHCI DRIVER; open list; Seungchull Suh; Daehwan Jung
>> Subject: Re: [PATCH] usb: dwc3: Clear DWC3_EVENT_PENDING when count is 0
>>
>>
>> On 1/5/2023 11:29 AM, Linyu Yuan wrote:
>>> On 1/2/2023 1:08 PM, JaeHun Jung wrote:
>>>> Sometimes very rarely, The count is 0 and the DWC3 flag is set has
>>>> status.
>>>> It must not have these status. Because, It can make happen interrupt
>>>> storming status.
>>> could you help explain without clear the flag, how interrupt storming
>>> happen ?
>>>
>>> as your change didn't touch any hardware register, i don't know how it
>>> fix storming.
>>>
> H/W interrupts are still occur on IP.

I guess we should fix it from IP layer.


but when checking DWC3_EVENT_PENDING flag, it will auto clear in dwc3 
thread irq handler.

there is one possible root cause is it cleared only after irq enabled in 
dwc3_process_event_buf(),

we should move unmask irq operation at end of this function.


> But. ISR doesn't handle it. Because of this
> "if (evt->flags & DWC3_EVENT_PENDING)"
>
> This is event values.
> (struct dwc3_event_buffer *) ev_buf = 0xFFFFFF883DBF1180 = kernel_size_le_lo32+0xFFFFFF883B391180 -> (
>          (void *) buf = 0xFFFFFFC00DBDD000 = end+0x337D000 -> ,
>          (void *) cache = 0xFFFFFF8839F54080 = kernel_size_le_lo32+0xFFFFFF88376F4080 -> ,
>          (unsigned int) length = 0x1000,
>          (unsigned int) lpos = 0x0,
>          (unsigned int) count = 0x0,
>          (unsigned int) flags = 0x00100001,
>          (dma_addr_t) dma = 0x00000008BD7D7000,
>
> *((struct dwc3_event_type *) 0xFFFFFF8839F54080) = (
>      is_devspec = 1,
>      type = 0,
>      reserved8_31 = 774)
>
> *((struct dwc3_event_devt  *) 0xFFFFFF8839F54080) = (
>      one_bit = 1,
>      device_event = 0,
>      type = 6, << DWC3_DEVICE_EVENT_SUSPEND
>      reserved15_12 = 0,
>      event_info = 3,
>      reserved31_25 = 0)
>
> Occurred interrupts are "DWC3_DEVICE_EVENT_SUSPEND".
> If when "count has 0" and DWC3_EVENT_PENDING are set at the same time than
>   ISR and bottom thread couldn't handle next interrupt.
> We guessing connected with "dwc3_gadget_process_pending_events()" function.
> But, We could not find reproduce way.
>
>
>>> storming from software layer ?
>>>
>>>> So, It have to clean up DWC3_EVENT_PENDING flags set when count is 0.
>>>> It means "There are no interrupts to handle.".
>>>>
>>>> (struct dwc3_event_buffer *) ev_buf = 0xFFFFFF883DBF1180 (
>>>>      (void *) buf = 0xFFFFFFC00DBDD000 = end+0x337D000,
>>>>      (void *) cache = 0xFFFFFF8839F54080,
>>>>      (unsigned int) length = 0x1000,
>>>>      (unsigned int) lpos = 0x0,
>>>>      (unsigned int) count = 0x0,
>>>>      (unsigned int) flags = 0x00000001,
>>>>      (dma_addr_t) dma = 0x00000008BD7D7000,
>>>>      (struct dwc3 *) dwc = 0xFFFFFF8839CBC880,
>>>>      (u64) android_kabi_reserved1 = 0x0),
>>>>
>>>> (time = 47557628930999, irq = 165, fn = dwc3_interrupt, latency = 0,
>>>> en = 1), (time = 47557628931268, irq = 165, fn = dwc3_interrupt,
>>>> latency = 0, en = 3), (time = 47557628932383, irq = 165, fn =
>>>> dwc3_interrupt, latency = 0, en = 1), (time = 47557628932652, irq =
>>>> 165, fn = dwc3_interrupt, latency = 0, en = 3), (time =
>>>> 47557628933768, irq = 165, fn = dwc3_interrupt, latency = 0, en = 1),
>>>> (time = 47557628934037, irq = 165, fn = dwc3_interrupt, latency = 0,
>>>> en = 3), (time = 47557628935152, irq = 165, fn = dwc3_interrupt,
>>>> latency = 0, en = 1), (time = 47557628935460, irq = 165, fn =
>>>> dwc3_interrupt, latency = 0, en = 3), (time = 47557628936575, irq =
>>>> 165, fn = dwc3_interrupt, latency = 0, en = 1), (time =
>>>> 47557628936845, irq = 165, fn = dwc3_interrupt, latency = 0, en = 3),
>>>> (time = 47557628937960, irq = 165, fn = dwc3_interrupt, latency = 0,
>>>> en = 1), (time = 47557628938229, irq = 165, fn = dwc3_interrupt,
>>>> latency = 0, en = 3), (time = 47557628939345, irq = 165, fn =
>>>> dwc3_interrupt, latency = 0, en = 1), (time = 47557628939652, irq =
>>>> 165, fn = dwc3_interrupt, latency = 0, en = 3), (time =
>>>> 47557628940768, irq = 165, fn = dwc3_interrupt, latency = 0, en = 1),
>>>> (time = 47557628941037, irq = 165, fn = dwc3_interrupt, latency = 0,
>>>> en = 3), (time = 47557628942152, irq = 165, fn = dwc3_interrupt,
>>>> latency = 0, en = 1), (time = 47557628942422, irq = 165, fn =
>>>> dwc3_interrupt, latency = 0, en = 3), (time = 47557628943537, irq =
>>>> 165, fn = dwc3_interrupt, latency = 0, en = 1), (time =
>>>> 47557628943806, irq = 165, fn = dwc3_interrupt, latency = 0, en = 3),
>>>> (time = 47557628944922, irq = 165, fn = dwc3_interrupt, latency = 0,
>>>> en = 1), (time = 47557628945229, irq = 165, fn = dwc3_interrupt,
>>>> latency = 0, en = 3), (time = 47557628946345, irq = 165, fn =
>>>> dwc3_interrupt, latency = 0, en = 1), (time = 47557628946614, irq =
>>>> 165, fn = dwc3_interrupt, latency = 0, en = 3), (time =
>>>> 47557628947729, irq = 165, fn = dwc3_interrupt, latency = 0, en = 1),
>>>> (time = 47557628947999, irq = 165, fn = dwc3_interrupt, latency = 0,
>>>> en = 3),
>>>>
>>>> Signed-off-by: JaeHun Jung <jh0801.jung@samsung.com>
>>>> ---
>>>>    drivers/usb/dwc3/gadget.c | 5 ++++-
>>>>    1 file changed, 4 insertions(+), 1 deletion(-) diff --git
>>>> a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c index
>>>> 789976567f9f..5d2d5a9b9915 100644
>>>> --- a/drivers/usb/dwc3/gadget.c
>>>> +++ b/drivers/usb/dwc3/gadget.c
>>>> @@ -4355,8 +4355,11 @@ static irqreturn_t dwc3_check_event_buf(struct
>>>> dwc3_event_buffer *evt)
>>>>         * irq event handler completes before caching new event to
>>>> prevent
>>>>         * losing events.
>>>>         */
>>>> -    if (evt->flags & DWC3_EVENT_PENDING)
>>>> +    if (evt->flags & DWC3_EVENT_PENDING) {
>>>> +        if (!evt->count)
>>>> +            evt->flags &= ~DWC3_EVENT_PENDING;
>>>>            return IRQ_HANDLED;
>>>> +    }
>>>>          count = dwc3_readl(dwc->regs, DWC3_GEVNTCOUNT(0));
>>>>        count &= DWC3_GEVNTCOUNT_MASK;
>>> how about below change ?
>>>
>>>          count = dwc3_readl(dwc->regs, DWC3_GEVNTCOUNT(0));
>>>          count &= DWC3_GEVNTCOUNT_MASK;
>>> -       if (!count)
>>> +       if (!count) {
>>> +               evt->flags &= ~DWC3_EVENT_PENDING;
>>>                  return IRQ_NONE;
>>> +       }
>> ignore my suggestion, add Thinh to comment.
>>>          evt->count = count;
>>>          evt->flags |= DWC3_EVENT_PENDING;
>>>