On 02/19/2018 09:19 AM, Minas Harutyunyan wrote: > On 2/17/2018 12:07 AM, Marek Vasut wrote: >> On 02/16/2018 06:59 AM, Minas Harutyunyan wrote: >>> On 2/15/2018 5:20 PM, Mirza Krak wrote: >>>> On 14 February 2018 at 13:07, Minas Harutyunyan >>>> <Minas.Harutyunyan at synopsys.com> wrote: >>>>> On 2/14/2018 12:57 PM, Mirza Krak wrote: >>>>>> On 8 February 2018 at 14:53, Minas Harutyunyan >>>>>> <Minas.Harutyunyan at synopsys.com> wrote: >>>> >>>> < snip > >>>> >>>>> >>>>> I reviewed your interrupt count log again. About 140,000 interrupts in 2 >>>>> seconds, obviously it's not SOF only interrupts. More probably, its NAK >>>>> respond interrupts to SSPLIT/CSPLIT transactions. For this case I can >>>>> recommend you to apply patch from Douglas Anderson: "[PATCH v2] usb: >>>>> dwc2: host: Don't retry NAKed transactions right away" which already >>>>> merged to 4.16-rc1. >>>>> >>>>> In your setups you see different behavior on different HUBs. Your HUBs >>>>> have different "TT think time": 8 and 32. In USB2.0 spec "TT think time" >>>>> described as follow "TT requires at most 8/32 FS bit times of inter >>>>> transaction gap on a full-/low-speed downstream bus". So, your "worst" >>>>> HUB with "TT think time"=8 sending more frequently SSPLIT/CSPLIT >>>>> transactions which replied by NAK. As result you see about 4 time more >>>>> interrupts comparing to "good" HUB. Could you please check interrupts >>>>> count for "good" HUB and check "4 time" hypothesis. >>>> >>>> Did some further testing. The "good" HUB is actually as bad as the >>>> "bad" HUB, and it was my setup that caused the different behavior. Did >>>> not use the same devices etc. >>>> >>>> Once I made sure that the configuration and setup was the same on both >>>> board I could see that the behaved similarly. And that is the >>>> following interrupt load: >>>> >>>> - BT USB (FS) = ~80k interrupts / second >>>> - Keyboard (FS) = ~80k interrupts / second >>>> - WiFI USB (HS) = ~8k interrupts / second >>>> >>>> After applying the suggested patch [1], it is steady around 8k >>>> interrupts / second no matter what device I connect (HS/FS, >>>> HUB/NO-HUB). Which is acceptable and usable. >>> >>> Great! >> >> So 8k IRQs per second is what I should expect from this HW with HS >> device attached, that's normal and cannot be reduced ? >> > If core acting as Host in Buffer DMA mode then 8k IRQs per second (SOF > interrupts) is expected if connected device(s) has periodic endpoint. Is there a way to reduce that or is that the absolute minimum in HS mode? -- Best regards, Marek Vasut
