linux-kernel - Re: [PATCH] usb: dwc3: Clear DWC3_EVENT

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Date:   Thu, 5 Jan 2023 11:35:17 +0800
From:   Linyu Yuan <quic_linyyuan@...cinc.com>
To:     JaeHun Jung <jh0801.jung@...sung.com>,
        Felipe Balbi <balbi@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Thinh Nguyen <Thinh.Nguyen@...opsys.com>
CC:     "open list:USB XHCI DRIVER" <linux-usb@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>,
        Seungchull Suh <sc.suh@...sung.com>,
        Daehwan Jung <dh10.jung@...sung.com>
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.
>
> 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@...sung.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;
>