Re: USB network gadget / DWC3 issue

[Ferry Toth <fntoth@gmail.com>]

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!

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.