Re: [PATCH v2 3/5] usb: dwc3: gadget: Write the event count in interrupt

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On 4 November 2016 at 07:41, Janusz Dziedzic <janusz.dziedzic@xxxxxxxxx> wrote:
> On 4 November 2016 at 02:31, John Youn <johnyoun@xxxxxxxxxxxx> wrote:
>>
>> Since we are saving the event count and handling the events in the
>> threaded interrupt handler, we can write and clear out the eventcount in
>> the hard interrupt handler itself.
>>
>> This behavior will be required for IP 3.00a cores that need to use
>> interrupt moderation as a workaround for an RTL issue were the interrupt
>> line cannot be masked between the hard/soft interrupt handler.
>>
>> Signed-off-by: John Youn <johnyoun@xxxxxxxxxxxx>
>> ---
>>  drivers/usb/dwc3/gadget.c | 4 ++--
>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
>> index a9c1d75..ac9eb39 100644
>> --- a/drivers/usb/dwc3/gadget.c
>> +++ b/drivers/usb/dwc3/gadget.c
>> @@ -2877,8 +2877,6 @@ static irqreturn_t dwc3_process_event_buf(struct dwc3_event_buffer *evt)
>>                  */
>>                 evt->lpos = (evt->lpos + 4) % DWC3_EVENT_BUFFERS_SIZE;
>>                 left -= 4;
>> -
>> -               dwc3_writel(dwc->regs, DWC3_GEVNTCOUNT(0), 4);
>>         }
>>
>>         evt->count = 0;
>> @@ -2928,6 +2926,8 @@ static irqreturn_t dwc3_check_event_buf(struct dwc3_event_buffer *evt)
>>         evt->count = count;
>>         evt->flags |= DWC3_EVENT_PENDING;
>>
Shouldn't you cache (somewhere):
u32 events[evt->buf + evt->lpos .... evt->buf + evt->lpos + count]

before you will giveback this to  HW (to be sure HW will not overwrite
this in case lot of events)?

>> +       dwc3_writel(dwc->regs, DWC3_GEVNTCOUNT(0), count);
>> +
After that evt->buf[lpos, lpos + count] seems goes back to HW, so
thread should not rely on this?

Or I miss something?

>>         /* Mask interrupt */
>>         reg = dwc3_readl(dwc->regs, DWC3_GEVNTSIZ(0));
>>         reg |= DWC3_GEVNTSIZ_INTMASK;
>> --
>
> Hello,
>
> Are we sure this will work fine with 2.60a?
>
> Some time ago I have similar code (introduce event_pop) and move
> dwc3_write(dwc->regs, DWC3_GEVNTCOUNT(0), 4)
> before
> dwc3_process_event_entry()
>
> And have some issues ...
> Didn't work correctly in my case.
>
> BR
> Janusz
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