Re: [BUG REPORT] usb: dwc3: Failure to enumerate from boot.

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

On Fri, May 09, 2025, Jakob Trumpower wrote:
> Hi Thinh,
> 
> Sorry about the formatting, I switched outlook to use plain text.
> 
> I removed the reset at init like you mentioned with the patch. As well as put the quirks back in for u2,u3 disable. I also had tried manually toggling the /sys/bus entries in the past, and would usually see the hub messages come back but the downstream device would still not enumerate. I tried it again with no change. Note: usb3 is the 2.0 controller for the same port.
> 
> root@ms-radar-01:~# cat /sys/bus/usb/devices/usb4/4-0:1.0/usb4-port1/disable                                                                                                                                    
> 0                                                                                                                        
> root@ms-radar-01:~# echo 1 >  /sys/bus/usb/devices/usb4/4-0\:1.0/usb4-port1/disable                                                                                                                                          
> root@ms-radar-01:~# echo 0 >  /sys/bus/usb/devices/usb4/4-0\:1.0/usb4-port1/disable                                                                                                                                          
> root@ms-radar-01:~# echo 1 >  /sys/bus/usb/devices/usb3/3-0\:1.0/usb3-port1/disable                                                                                                                                          
> root@ms-radar-01:~# echo 0 >  /sys/bus/usb/devices/usb3/3-0\:1.0/usb3-port1/disable  
> 
> Here I am toggling authorized instead and I do see some messages, but still no device:
>                                                                                                          
> root@ms-radar-01:~#         sudo echo 0 > /sys/bus/usb/devices/usb4/authorized                                                                                                                                  
> root@ms-radar-01:~#         sudo echo 1 > /sys/bus/usb/devices/usb4/authorized                                                                                                                                  
> [ 2208.950615] hub 4-0:1.0: USB hub found                                                                                                                                                                       
> [ 2208.954440] hub 4-0:1.0: 1 port detected                                                                                                                                                                     
> [ 2208.960168] usb usb4: authorized to connect                                                                             
> 
> 
> Then once again, I cycle the usb C connector and it comes up:
> root@ms-radar-01:~# [  323.210398] usb 4-1: new SuperSpeed USB device number 2 using xhci-hcd                                                                                                                   
> [  323.511597] usb 4-1: New USB device found, idVendor=0b95, idProduct=1790, bcdDevice= 2.00                                                                                                                    
> [  323.519776] usb 4-1: New USB device strings: Mfr=1, Product=2, SerialNumber=3                                                                                                                                
> [  323.526917] usb 4-1: Product: AX88179A                                                                                                                                                                       
> [  323.530672] usb 4-1: Manufacturer: ASIX                                                                                                                                                                      
> [  323.534506] usb 4-1: SerialNumber: 00000000000FF3                                                                                                                                                            
> [  323.913798] cdc_ncm 4-1:2.0: MAC-Address: a0:ce:c8:ba:a9:44                                                                                                                                                  
> [  323.919389] cdc_ncm 4-1:2.0: setting rx_max = 16384                                                                                                                                                          
> [  323.937168] cdc_ncm 4-1:2.0: setting tx_max = 16384                                                                                                                                                          
> [  323.951984] cdc_ncm 4-1:2.0 eth0: register 'cdc_ncm' at usb-xhci-hcd.2.auto-1, CDC NCM (NO ZLP), a0:ce:c8:ba:a9:44                                                                                           
> [  324.103396] cdc_ncm 4-1:2.0 enu1c2: renamed from eth0 
> 
> Very strange the plug cycle seems to fix the controller reliably. Also to note that it happens to every 3.0 device I have tested. I have a change order for our next board revision to toggle the VBUS with a GPIO, but not an ideal solution.
> 
> I know USB and these controllers are extremely complex so I appreciate your time and expertise.
> 
> Let me know if you can think of any other registers/experiments we can try.
> 

Thanks for the experiments. 

Ok, this is odd. It's not what I thought. If the usb3 port detection
fails a few times, then it should fallback to usb2 connection.

Let's check the portsc:
# cat /sys/kernel/debug/usb/xhci/<your_controller>/ports/**/*

Also, can you add this to the kernel cmdline to capture the xhci
tracepoints:

"xhci_hcd.dyndbg=+p trace_event=xhci-hcd trace_buf_size=30M"

# cat /sys/kernel/debug/tracing/trace > tracepoints.log

Thanks,
Thinh