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

[정재훈 <jh0801.jung@samsung.com>]

> -----Original Message-----
> From: Linyu Yuan [mailto:quic_linyyuan@quicinc.com]
> 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.
But. ISR doesn't handle it. Because of this
"if (evt->flags & DWC3_EVENT_PENDING)"

This is event values.
(struct dwc3_event_buffer *) ev_buf = 0xFFFFFF883DBF1180 = kernel_size_le_lo32+0xFFFFFF883B391180 -> (
        (void *) buf = 0xFFFFFFC00DBDD000 = end+0x337D000 -> ,
        (void *) cache = 0xFFFFFF8839F54080 = kernel_size_le_lo32+0xFFFFFF88376F4080 -> ,
        (unsigned int) length = 0x1000,
        (unsigned int) lpos = 0x0,
        (unsigned int) count = 0x0,
        (unsigned int) flags = 0x00100001,
        (dma_addr_t) dma = 0x00000008BD7D7000,

*((struct dwc3_event_type *) 0xFFFFFF8839F54080) = (
    is_devspec = 1,
    type = 0,
    reserved8_31 = 774)

*((struct dwc3_event_devt  *) 0xFFFFFF8839F54080) = (
    one_bit = 1,
    device_event = 0,
    type = 6, << DWC3_DEVICE_EVENT_SUSPEND
    reserved15_12 = 0,
    event_info = 3,
    reserved31_25 = 0)

Occurred interrupts are "DWC3_DEVICE_EVENT_SUSPEND".
If when "count has 0" and DWC3_EVENT_PENDING are set at the same time than
 ISR and bottom thread couldn't handle next interrupt.
We guessing connected with "dwc3_gadget_process_pending_events()" function.
But, We could not find reproduce way.


> > 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@samsung.com>
> >> ---
> >>   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;
> > +       }
> ignore my suggestion, add Thinh to comment.
> >
> >         evt->count = count;
> >         evt->flags |= DWC3_EVENT_PENDING;
> >