On Fri, Aug 09, 2024, Thinh Nguyen wrote: > On Thu, Aug 08, 2024, Selvarasu Ganesan wrote: > > > > On 8/8/2024 6:45 AM, Thinh Nguyen wrote: > > > On Wed, Aug 07, 2024, Selvarasu Ganesan wrote: > > >> On 8/7/2024 6:08 AM, Thinh Nguyen wrote: > > >>> On Fri, Jul 19, 2024, Selvarasu Ganesan wrote: > > >>>> In certain scenarios, there is a chance that the CPU may not be > > >>>> scheduled the bottom half of dwc3 interrupt. This is because the CPU > > >>>> may hang up where any work queue lockup has happened for the same CPU > > >>>> that is trying to schedule the dwc3 thread interrupt. In this scenario, > > >>>> the USB can enter runtime suspend as the bus may idle for a longer time > > >>>> , or user can reconnect the USB cable. Then, the dwc3 event interrupt > > >>>> can be enabled when runtime resume is happening with regardless of the > > >>>> previous event status. This can lead to a dwc3 IRQ storm due to the > > >>>> return from the interrupt handler by checking only the evt->flags as > > >>>> DWC3_EVENT_PENDING, where the same flag was set as DWC3_EVENT_PENDING > > >>>> in previous work queue lockup. > > >>>> Let's consider the following sequences in this scenario, > > >>>> > > >>>> Call trace of dwc3 IRQ after workqueue lockup scenario > > >>>> ====================================================== > > >>>> IRQ #1: > > >>>> ->dwc3_interrupt() > > >>>> ->dwc3_check_event_buf() > > >>>> ->if (evt->flags & DWC3_EVENT_PENDING) > > >>>> return IRQ_HANDLED; > > >>>> ->evt->flags |= DWC3_EVENT_PENDING; > > >>>> ->/* Disable interrupt by setting DWC3_GEVNTSIZ_INTMASK in > > >>>> DWC3_GEVNTSIZ > > >>>> ->return IRQ_WAKE_THREAD; // No workqueue scheduled for dwc3 > > >>>> thread_fu due to workqueue lockup > > >>>> even after return IRQ_WAKE_THREAD > > >>>> from top-half. > > >>>> > > >>>> Thread #2: > > >>>> ->dwc3_runtime_resume() > > >>>> ->dwc3_resume_common() > > >>>> ->dwc3_gadget_resume() > > >>>> ->dwc3_gadget_soft_connect() > > >>>> ->dwc3_event_buffers_setup() > > >>>> ->/*Enable interrupt by clearing DWC3_GEVNTSIZ_INTMASK in > > >>>> DWC3_GEVNTSIZ*/ > > >>>> > > >>>> Start IRQ Storming after enable dwc3 event in resume path > > >>>> ========================================================= > > >>>> CPU0: IRQ > > >>>> dwc3_interrupt() > > >>>> dwc3_check_event_buf() > > >>>> if (evt->flags & DWC3_EVENT_PENDING) > > >>>> return IRQ_HANDLED; > > >>>> > > >>>> CPU0: IRQ > > >>>> dwc3_interrupt() > > >>>> dwc3_check_event_buf() > > >>>> if (evt->flags & DWC3_EVENT_PENDING) > > >>>> return IRQ_HANDLED; > > >>>> .. > > >>>> .. > > >>>> > > >>>> To fix this issue by avoiding enabling of the dwc3 event interrupt in > > >>>> the runtime resume path if dwc3 event processing is in progress. > > >>>> > > >>>> Signed-off-by: Selvarasu Ganesan <selvarasu.g@xxxxxxxxxxx> > > >>>> --- > > >>>> drivers/usb/dwc3/core.c | 8 ++++++-- > > >>>> 1 file changed, 6 insertions(+), 2 deletions(-) > > >>>> > > >>>> diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c > > >>>> index cb82557678dd..610792a70805 100644 > > >>>> --- a/drivers/usb/dwc3/core.c > > >>>> +++ b/drivers/usb/dwc3/core.c > > >>>> @@ -549,8 +549,12 @@ int dwc3_event_buffers_setup(struct dwc3 *dwc) > > >>>> lower_32_bits(evt->dma)); > > >>>> dwc3_writel(dwc->regs, DWC3_GEVNTADRHI(0), > > >>>> upper_32_bits(evt->dma)); > > >>>> - dwc3_writel(dwc->regs, DWC3_GEVNTSIZ(0), > > >>>> - DWC3_GEVNTSIZ_SIZE(evt->length)); > > >>>> + > > >>>> + /* Skip enable dwc3 event interrupt if event is processing in middle */ > > >>>> + if (!(evt->flags & DWC3_EVENT_PENDING)) > > >>>> + dwc3_writel(dwc->regs, DWC3_GEVNTSIZ(0), > > >>>> + DWC3_GEVNTSIZ_SIZE(evt->length)); > > >>>> + > > >>>> dwc3_writel(dwc->regs, DWC3_GEVNTCOUNT(0), 0); > > >>>> > > >>>> return 0; > > >>>> -- > > >>>> 2.17.1 > > >>>> > > >>> We're not waking up from a hibernation. So after a soft-reset and > > >>> resume, the events that weren't processed are stale. They should be > > >>> processed prior to entering suspend or be discarded before resume. > > >>> > > >>> The synchronize_irq() during suspend() was not sufficient to prevent > > >>> this? What are we missing here. > > >>> > > >>> Thanks, > > >>> Thinh > > >> I don’t think the triggering of interrupt would not be stopped even if > > >> do soft reset. It's because of event count is may be valid . > > > Ok. I think I see what you're referring to when you say "event is > > > processing in the middle" now. > > > > > > What you want to check is probably this in dwc3_event_buffers_setup(). > > > Please confirm: > > > > > > if (dwc->pending_events) > > > dwc3_writel(dwc->regs, DWC3_GEVNTSIZ(0), > > > DWC3_GEVNTSIZ_INTMASK | DWC3_GEVNTSIZ_SIZE(evt->length)); > > > else > > > dwc3_writel(dwc->regs, DWC3_GEVNTSIZ(0), DWC3_GEVNTSIZ_SIZE(evt->length)); > > > > Yes, we are expecting the same. But, we must verify the status of > > evt->flags, which will indicate whether the event is currently > > processing in middle or not. The below code is for the reference. > > > > if (!(evt->flags & DWC3_EVENT_PENDING)) > > dwc3_writel(dwc->regs, DWC3_GEVNTSIZ(0), > > DWC3_GEVNTSIZ_SIZE(evt->length)); > > else > > dwc3_writel(dwc->regs, DWC3_GEVNTSIZ(0), > > DWC3_GEVNTSIZ_INTMASK | DWC3_GEVNTSIZ_SIZE(evt->length)); > > So, this happens while pending_events is set right? I need to review > this runtime suspend flow next week. Something doesn't look right. When > there's a suspend/resume runtime or not, there's a soft disconnect. We > shouldn't be processing any event prior to going into suspend. Also, we Clarification: I mean we shouldn't process any event that happened prior to suspend on resume because there was a disconnect. > shouldn't be doing soft-disconnect while connected and in operation > unless we specifically tell it to. Thinh
