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

[Linyu Yuan <quic_linyyuan@xxxxxxxxxxx>]

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@xxxxxxxxxxx>
> ---
>   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;
+       }

        evt->count = count;
        evt->flags |= DWC3_EVENT_PENDING;