On Fri, Jan 06, 2023, Linyu Yuan wrote: > On 1/5/2023 5:54 PM, 정재훈 wrote: > > > > > -----Original Message----- > > > From: Linyu Yuan [mailto:quic_linyyuan@xxxxxxxxxxx] > > > 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. > How are you certain the problem is 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. > This interrupt storm can happen because we clear the evt->flags _after_ we unmask the interrupt. This was done to prevent false interrupt from delay interrupt deassertion, which can be a problem for legacy pci interrupt. see 7441b273388b ("usb: dwc3: gadget: Fix event pending check") The change JaeHun Jung did should be fine. BR, Thinh
