Re: lan78xx: About 8000 usb interrupts per second when idle

[Jisheng Zhang <Jisheng.Zhang@synaptics.com>]

On Tue, 9 Apr 2019 09:28:16 +0000 Minas Harutyunyan wrote:


> 
> Hi Stefan,
> 
> > Hi Minas,
> >
> > Am 09.04.19 um 08:54 schrieb Jisheng Zhang:  
> >> On Mon, 8 Apr 2019 16:05:51 +0800 Jisheng Zhang wrote:
> >>  
> >>> Hi Stefan,
> >>>
> >>> On Mon, 8 Apr 2019 09:57:14 +0200 Stefan Wahren wrote:
> >>>  
> >>>>
> >>>> Hi Jisheng,
> >>>>
> >>>>
> >>>> thanks for sending this patch.  I already reported this issue
> >>>> last year [1], but Microchip wasn't able to provide a fix.
> >>>>
> >>>> I will give it a try.
> >>>>  
> >>>>> The second one: 8000 usb interrupts per second when idle.
> >>>>> This is abnormal. any idea? Is it due to the lan78xx?  
> >>>> Does this downstream patch [2] improve your situation?  
> >>> Thanks a lot. Will try the patch tonight.  
> >> I tried this patch, it doesn't help. One more observation: if I
> >> ifconfig eth0 down, I can still get 8000 usb interrupts per second.
> >>  Not sure whether this is usb issue or not.  
> >
> > Jisheng reports a lot of USB interrupts while the lan78xx driver on
> > Raspberry Pi 3B+ is in idle.
> >
> > Any suggestions to narrow this down?  
> 
> dwc2 in host mode enable SOF interrupts if any periodic EP are in use.
> So, 8000 interrupts per second is expectant behavior.

Makes sense. 8 microframes each 1ms, so 8*1000 = 8000 interrupts/s