Re: [PATCH] usb: dwc3: Clear DWC3_EVENT_PENDING when count is 0
From: Linyu Yuan
Date: Mon Jan 09 2023 - 20:56:35 EST
On 1/10/2023 2:28 AM, Thinh Nguyen wrote:
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?
I think all IRQ is from DWC3 controller IP. if it is not IP layer, could
you share how to prevent from SW layer ?
seem IRQ can happen when event count is zero , why this can happen ?
does it mean event count register is not trust ?
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.
thanks for explain, i didn't know that.
see 7441b273388b ("usb: dwc3: gadget: Fix event pending check")
The change JaeHun Jung did should be fine.
agree.
BR,
Thinh