Hi, On Thu, Jun 13, 2013 at 08:26:12PM +0800, Huang Rui wrote: > > > I was reading dwc3 codes and found that during the process of > > > configuring event buffer (dwc3_event_buffers_setup), it only write the > > > size of the buffer and doesn't write interrupt mask bit into GEVNTSIZ > > > register like below, > > > > > > dwc3_writel(dwc->regs, DWC3_GEVNTSIZ(n), > > > evt->length & 0xffff); > > > > > > But in spec, it suggests that write this bit to prevent the interrupt > > > from being generated in an event buffer configuration. So need we set > > > > where does it say that ? I just re-read details about that bit and all > > it says is that it can be used to mask the interrupt, but events will > > still be queued. Maybe I'm missing some part. Which revision of the > > databook are you reading ? > > Thanks a lot to look back into this issue. I read version 2.50a, in > section 8.2.2, the step 3 to configure an Event Buffer describes: > > "Writes the size of the buffer and interrupt mask into GEVNTSIZn. > Depending on your system interrupt latency, enough Event Buffer space > must be allocated to avoid lost interrupts or reduced performance." > > If I misunderstood, please correct me. but we are writing Interrupt mask bit, just always writing 0 :-) > > Anyway, we don't really need that bit right now because linux will only > > enable the IRQ line after request_*irq() has been called and we're > > setting up our event buffers before calling that. > > > > Yeah, when the event buffers are set up, it must not encounter any > interrupts. right. > > OTOH, we could use that bit as means to get rid of IRQF_ONESHOT from > > DWC3 driver. > > > > Thanks to teach me. The IRQF_ONESHOT interrupt should also prevent the > other interrupts until the current thread has been run, just like the > function of interrupt mask bit, am I right? that's correct. IRQ subsystem makes sure to keep IRQs masked until thread has finished running. > > Can you test a patch for me ? I don't have access to HW right now. I > > assume the patch below works fine, does it ? > > > > Sorry, I haven't got the board yet. Your patch looks good, and I will > test it as soon as I get HW. alright, so it's likely that I'll get access to my stuff back before. Anyway, if you happen to have time, I'd be glad to see a Tested-by, always good to test on more than a single platform. -- balbi
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