Re: USB network gadget / DWC3 issue

[Thinh Nguyen <Thinh.Nguyen@synopsys.com>]

Thinh Nguyen wrote:
> Ferry Toth wrote:
>> Op 07-04-2021 om 15:34 schreef Andy Shevchenko:
>>> On Wed, Apr 7, 2021 at 3:24 AM Thinh Nguyen
>>> <Thinh.Nguyen@synopsys.com> wrote:
>>>> Thinh Nguyen wrote:
>>> ...
>>>
>>>>> I took a look at the "bad" and "normal" tracepoints. There are a few
>>>>> 1-second delays where the host tried to bring the device back and
>>>>> resume from low power:
>>>>>
>>>>>       ksoftirqd/0-10      [000] d.s.   231.501808:
>>>>> dwc3_gadget_ep_cmd: ep3in: cmd 'Update Transfer' [60007] params
>>>>> 00000000 00000000 00000000 --> status: Successful
>>>>>       ksoftirqd/0-10      [000] d.s.   231.501809: dwc3_readl: addr
>>>>> 00000000d68ecd36 value 0000a610
>>>>>       ksoftirqd/0-10      [000] d.s.   231.501810: dwc3_writel: addr
>>>>> 00000000d68ecd36 value 0000a710
>>>>>            <idle>-0       [000] d.h.   232.499418: dwc3_readl: addr
>>>>> 00000000a15e0e35 value 00000034
>>>>>            <idle>-0       [000] d.h.   232.499423: dwc3_readl: addr
>>>>> 00000000bb67b585 value 00001000
>>>>>            <idle>-0       [000] d.h.   232.499425: dwc3_writel: addr
>>>>> 00000000bb67b585 value 80001000
>>>>>            <idle>-0       [000] d.h.   232.499427: dwc3_writel: addr
>>>>> 00000000a15e0e35 value 00000034
>>>>>       irq/15-dwc3-476     [000] d...   232.499480: dwc3_event: event
>>>>> (00000401): WakeUp [U0]
>>>>>       irq/15-dwc3-476     [000] d...   232.499492: dwc3_event: event
>>>>> (00000401): WakeUp [U0]
>>>>>       irq/15-dwc3-476     [000] d...   232.499496: dwc3_event: event
>>>>> (00006088): ep2out: Transfer In Progress [0] (SIm)
>>>>>       irq/15-dwc3-476     [000] d...   232.499501:
>>>>> dwc3_complete_trb: ep2out: trb 00000000c7ce524e (E179:D170) buf
>>>>> 0000000008273540 size 1463 ctrl 00000818 (hlcS:sC:normal)
>>>>>       irq/15-dwc3-476     [000] d...   232.499518:
>>>>> dwc3_gadget_giveback: ep2out: req 0000000012e296cf length 73/1536
>>>>> zsI ==> 0
>>>>>       irq/15-dwc3-476     [000] d...   232.499562: dwc3_ep_queue:
>>>>> ep2out: req 0000000012e296cf length 0/1536 zsI ==> -115
>>>>>       irq/15-dwc3-476     [000] d...   232.499601: dwc3_prepare_trb:
>>>>> ep2out: trb 000000008c083777 (E180:D170) buf 0000000002a7e9c0 size
>>>>> 1536 ctrl 00000819 (HlcS:sC:normal)
>>>>>
>>>>>
>>>>> Your device is operating in highspeed right? Try to turn off LPM from
>>>>> host and see if that helps with the speed throttling issue. (If you're
>>>>> using xHCI host, then set XHCI_HW_LPM_DISABLE). It may also help with
>>>>> the connection issue you saw.
>>>>>
>>>>> It seems to be an issue from host, but I can't tell for sure unless we
>>>>> have some USB traffic analyzer that shows what's going on. Have you
>>>>> tried different hosts?
>>>>>
>>>> You can also disable LPM from the gadget side by setting
>>>> dwc->dis_enblslpm_quirk.
>>> Ferry, it can be done by adding a corresponding property to the
>>> dwc3-pci.c for Intel Merrifield platform. I'll check also for my case
>>> and perhaps I can collect some traces in my case later on when I have
>>> more time for that.
>>>
>> Ok thanks all. Here is what I tried:
>>
>> Another computer (Acer 720P brainwashed chromebook), I tried both full
>> speed and high speed. Still throttling but less bad.
>>
>> Then on desktop, with Edison kernel 5.12-rc5 as above + this patch:
>>
>> diff --git a/drivers/usb/dwc3/dwc3-pci.c b/drivers/usb/dwc3/dwc3-pci.c
>>
>> index 4c5c6972124a..a9268c085840 100644
>>
>> --- a/drivers/usb/dwc3/dwc3-pci.c
>>
>> +++ b/drivers/usb/dwc3/dwc3-pci.c
>>
>> @@ -122,6 +122,7 @@ static const struct property_entry
>> dwc3_pci_mrfld_properties[] = {
>>
>> PROPERTY_ENTRY_STRING("linux,extcon-name", "mrfld_bcove_pwrsrc"),
>>
>> PROPERTY_ENTRY_BOOL("snps,dis_u3_susphy_quirk"),
>>
>> PROPERTY_ENTRY_BOOL("snps,dis_u2_susphy_quirk"),
>>
>> + PROPERTY_ENTRY_BOOL("snps,dis_enblslpm_quirk"),
>>
>> PROPERTY_ENTRY_BOOL("linux,sysdev_is_parent"),
>>
>> {}
>>
>> };
>>
>> This fixes the throttling but reveals I had actually at least 2 bugs:
>>
>> 1) throttling due to LPM, this seems solved now, thanks to much!
> 
> Now that we can confirm the speed throttling is related to LPM. We can
> try to experiment further. (IMO, LPM is an important feature and
> totally disabling LPM seems like using a sledgehammer to crack a nut)
> 
> I suspect that your phy/HW has a higher low power exit latency. I don't
> think you provided any HIRD threshold property in your setup right? So
> by default, dwc3 sets the base line BESL value to 1 (or 150us). Unless
> you know what your phy/HW is capable of, try to test and increase the
> recommended BESL value. The range can be from 0 to 15 where 0 is 150us
> and 15 is 10ms. Maybe try 6 (i.e. 1ms).
> 

Correction... 0 is 125us, 1 is 150us.