On Sat, Feb 01, 2025, Badhri Jagan Sridharan wrote: > On Fri, Jan 31, 2025 at 4:09 PM Thinh Nguyen <Thinh.Nguyen@xxxxxxxxxxxx> wrote: > > > > Hmm... Can you try this instead: > > Thanks, this seems to be working ! > I also sent out the following as there isn't a way to enable interrupt > moderation through the device tree node: > https://urldefense.com/v3/__https://lore.kernel.org/all/20250202035100.31235-1-badhri@xxxxxxxxxx/__;!!A4F2R9G_pg!e6BA5h7M1-HZjrH2-bLVF0YbmzStu9ASv1lkZudrnyX2RFDlDUnrlFCgMdbwXcbTrMsVUQvgnpRmYxmcV-w$ > https://urldefense.com/v3/__https://lore.kernel.org/all/20250202035100.31235-2-badhri@xxxxxxxxxx/__;!!A4F2R9G_pg!e6BA5h7M1-HZjrH2-bLVF0YbmzStu9ASv1lkZudrnyX2RFDlDUnrlFCgMdbwXcbTrMsVUQvgnpRm9hdUtjE$ > > > > > diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c > > index 0fe92c0fb520..c1b5a3742ab4 100644 > > --- a/drivers/usb/dwc3/gadget.c > > +++ b/drivers/usb/dwc3/gadget.c > > @@ -5737,14 +5737,20 @@ static irqreturn_t dwc3_process_event_buf(struct dwc3_event_buffer *evt) > > dwc3_writel(dwc->regs, DWC3_GEVNTSIZ(0), > > DWC3_GEVNTSIZ_SIZE(evt->length)); > > > > + /* > > + * Keep the clearing of DWC3_EVENT_PENDING after the interrupt unmask > > + * but before the clearing of DWC3_GEVNTCOUNT_EHB. > > + */ > > + evt->flags &= ~DWC3_EVENT_PENDING; > > + > > + /* Ensure the flag is updated before clearing DWC3_GEVNTCOUNT_EHB */ > > + wmb(); > > I still have one more question though :) > Wondering why not move this code about the DWC3_GEVNTSIZ write where > the interrupt is actually unmasked that way this would also work for > systems which dont have interrupt moderation enabled right ? > It's mainly for PCI devices. PCI devices sends assert/de-assert messages to represent the level interrupt for PCI legacy interrupt. The de-assert interrupt message may not be received right after masking the interrupt, such as due to system latency. This may trigger a scheduling of the TH again. If there's new event received during the TH, this will cause a race and dwc3 driver may overwrite the cached events (a window between clearing the flag and unmasking of interrupt). We may have a potential issue for platform with devices with shared interrupt too (though I haven't seen report of this issue before). BR, Thinh
