Re: USB network gadget / DWC3 issue

[Ferry Toth <fntoth@gmail.com>]

Op 09-04-2021 om 15:26 schreef Ferry Toth:
> Hi,
>
> Op 08-04-2021 om 23:12 schreef Thinh Nguyen:
>> 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).
>>
>> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
>> index 60e850a395a2..423533df8927 100644
>> --- a/drivers/usb/dwc3/gadget.c
>> +++ b/drivers/usb/dwc3/gadget.c
>> @@ -2895,7 +2895,7 @@ static void dwc3_gadget_config_params(struct 
>> usb_gadget *g,
>>                   * recommended BESL baseline to 1 and clamp the BESL 
>> deep to be
>>                   * within 2 to 15.
>>                   */
>> -               params->besl_baseline = 1;
>> +               params->besl_baseline = 6;
>>                  if (dwc->is_utmi_l1_suspend)
>>                          params->besl_deep =
>>                                  clamp_t(u8, dwc->hird_threshold, 2, 
>> 15);
>>
> I will try and report back, hopefully this evening.
I tried this and it seems to have the same effect as dis_enblslpm_quirk
>>
>>> 2) a problem with usb plug detection
>>>
>>> When I unplug/replug the gadget cable I need to do that at least 
>>> another
>>> time before gadget is detected. So unplug/replug/unplug/replug seems to
>>> work.
>>>
>>> Also this platform has a HW switch to select host/device mode, with
>>> separate connectors for host and device.
>>>
>>> When I flip the switch to host it immediately changes to host.
>>>
>>> Flipping to device leaves the LEDs on my connected usb hub on, so it's
>>> still powered (but not operational).
>>>
>>> Flipping fast host/device (within 1/2 sec) hub LEDs turns off. But I
>>> still need to additionally unplug/replug the gadget cable to get 
>>> that to
>>> work.
>>>
>> The connection issue can come from different things. Please narrow it 
>> down
>> and make sure that you don't use any defective cable or bad hub. Even 
>> then,
>> it's difficult to determine whose fault it is from just the dmesg and 
>> driver
>> logs alone without looking at the USB traffic at the packet level.
>>
>> Btw, is your setup DRD? If you're switching mode, then I know that 
>> dwc3 right
>> now doesn't implement mode switching correctly.
> Yes, we use Extcon driver to support DRD.
>> You can see the discussion we have here:
>> https://lore.kernel.org/linux-usb/20210108015115.27920-1-john.stultz@linaro.org/T/#t 
>>
> I see, that might indeed be related. I will try the patches to see if 
> that works and report back.

I applied both patches:

usb: dwc3: Trigger a GCTL soft reset when switching modes in DRD

usb: dwc3: Fix DRD mode change sequence following programming guide

It doesn't have an effect on the need to unplug/replug neither on the 
problems switch from host/device mode.

But it doesn't hurt either.

>> BR,
>> Thinh