Messages in this thread | ![/](/images/icornerl.gif) | | Date | Thu, 25 Apr 2024 23:27:47 +0200 | Subject | Re: [PATCH v4] usb: gadget: u_ether: Replace netif_stop_queue with netif_device_detach | From | Ferry Toth <> |
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Hi,
Op 17-04-2024 om 17:13 schreef Hardik Gajjar: > On Tue, Apr 16, 2024 at 04:48:32PM +0300, Andy Shevchenko wrote: >> On Thu, Apr 11, 2024 at 10:52:36PM +0200, Ferry Toth wrote: >>> Op 11-04-2024 om 18:39 schreef Andy Shevchenko: >>>> On Thu, Apr 11, 2024 at 04:26:37PM +0200, Hardik Gajjar wrote: >>>>> On Wed, Apr 10, 2024 at 08:37:42PM +0300, Andy Shevchenko wrote: >>>>>> On Sun, Apr 07, 2024 at 10:51:51PM +0200, Ferry Toth wrote: >>>>>>> Op 05-04-2024 om 13:38 schreef Hardik Gajjar: >> >> ... >> >>>>>>> Exactly. And this didn't happen before the 2 patches. >>>>>>> >>>>>>> To be precise: /sys/class/net/usb0 is not removed and it is a link, the link >>>>>>> target /sys/devices/pci0000:00/0000:00:11.0/dwc3.0.auto/gadget.0/net/usb0 no >>>>>>> longer exists >>>>> So, it means that the /sys/class/net/usb0 is present, but the symlink is >>>>> broken. In that case, the dwc3 driver should recreate the device, and the >>>>> symlink should become active again >>> >>> Yes, on first enabling gadget (when device mode is activated): >>> >>> root@yuna:~# ls /sys/devices/pci0000:00/0000:00:11.0/dwc3.0.auto/gadget.0/ >>> driver net power sound subsystem suspended uevent >>> >>> Then switching to host mode: >>> >>> root@yuna:~# ls /sys/devices/pci0000:00/0000:00:11.0/dwc3.0.auto/gadget.0/ >>> ls: cannot access >>> '/sys/devices/pci0000:00/0000:00:11.0/dwc3.0.auto/gadget.0/': No such file >>> or directory >>> >>> Then back to device mode: >>> >>> root@yuna:~# ls /sys/devices/pci0000:00/0000:00:11.0/dwc3.0.auto/gadget.0/ >>> driver power sound subsystem suspended uevent >>> >>> net is missing. But, network functions: >>> >>> root@yuna:~# ping 10.42.0.1 >>> PING 10.42.0.1 (10.42.0.1): 56 data bytes >>> >>> Mass storage device is created and removed each time as expected. >> >> So, what's the conclusion? Shall we move towards revert of those two changes? > > > As promised, I have the tested the this patch with the dwc3 gadget. I could not reproduce > the issue. > > I can see the usb0 exist all the time and accessible regardless of the role switching of the USB mode (peripheral <-> host) > > Following are the logs: > //Host to device > > console:/sys/bus/platform/devices/a800000.ssusb # echo "peripheral" > mode > console:/sys/bus/platform/devices/a800000.ssusb # ls a800000.dwc3/gadget/net/ > usb0 > > //device to host > console:/sys/bus/platform/devices/a800000.ssusb # echo "host" > mode > console:/sys/bus/platform/devices/a800000.ssusb # ls a800000.dwc3/gadget/net/ > usb0
That is weird. When I switch to host mode (using the physical switch), the whole gadget directory is removed (now testing 6.9.0-rc5)
Switching back to device mode, that gadget directory is recreated. And gadget/sound as well, but not gadget/net.
> s a800000.dwc3/gadget/net/usb0 < > addr_assign_type duplex phys_port_name > addr_len flags phys_switch_id > address gro_flush_timeout power > broadcast ifalias proto_down > carrier ifindex queues > carrier_changes iflink speed > carrier_down_count link_mode statistics > carrier_up_count mtu subsystem > dev_id name_assign_type tx_queue_len > dev_port netdev_group type > device operstate uevent > dormant phys_port_id waiting_for_supplier > console:/sys/bus/platform/devices/a800000.ssusb # ifconfig -a usb0 > usb0 Link encap:Ethernet HWaddr 3a:8b:63:97:1a:9a > BROADCAST MULTICAST MTU:1500 Metric:1 > RX packets:0 errors:0 dropped:0 overruns:0 frame:0 > TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 > collisions:0 txqueuelen:1000 > RX bytes:0 TX bytes:0 > > console:/sys/bus/platform/devices/a800000.ssusb # > > I strongly advise against reverting the patch solely based on the observed issue of removing the /sys/class/net/usb0 directory while the usb0 interface remains available.
There's more to it. I also mentioned that switching the role or unplugging the cable leaves the usb0 connection.
I have while in host mode: root@yuna:~# ifconfig -a usb0 usb0: flags=-28605<UP,BROADCAST,RUNNING,MULTICAST,DYNAMIC> mtu 1500 inet 10.42.0.221 netmask 255.255.255.0 broadcast 10.42.0.255 inet6 fe80::a8bb:ccff:fedd:eef1 prefixlen 64 scopeid 0x20<link>
You don't see that because you didn't create a connection at all.
> Instead, I recommend enabling FTRACE to trace the functions involved and identify which faulty call is responsible for removing usb0.
Switching from device -> host -> device:
root@yuna:~# trace-cmd record -p function_graph -l *gether_* plugin 'function_graph' Hit Ctrl^C to stop recording ^CCPU0 data recorded at offset=0x1c8000 188 bytes in size (4096 uncompressed) CPU1 data recorded at offset=0x1c9000 0 bytes in size (0 uncompressed) root@yuna:~# trace-cmd report cpus=2 irq/68-dwc3-725 [000] 514.575337: funcgraph_entry: # 2079.480 us | gether_disconnect(); irq/68-dwc3-946 [000] 524.263731: funcgraph_entry: + 11.640 us | gether_disconnect(); irq/68-dwc3-946 [000] 524.263743: funcgraph_entry: ! 116.520 us | gether_connect(); irq/68-dwc3-946 [000] 524.268029: funcgraph_entry: # 2057.260 us | gether_disconnect(); irq/68-dwc3-946 [000] 524.270089: funcgraph_entry: ! 109.000 us | gether_connect();
> According to current kernel architecture of u_ether driver, only gether_cleanup should remove the usb0 interface along with its kobject and sysfs interface. > I suggest sharing the analysis here to understand why this practice is not followed in your use case or driver ?
Yes, I'll try to trace where that happens.
Nevertheless, the disappearance of the net/usb0 directory seems harmless? But the usb: net device remaining after disconnect or role switch is not good, as the route remains.
May be they are 2 separate problems. Could you try to reproduce what happens if you make eem connection and then unplug?
> I am curious why the driver was developed without adhering to the kernel's gadget architecture. > >> >>>>> I have the dwc3 IP base usb controller, Let me check with this patch and >>>>> share result here. May be we need some fix in dwc3 >>> Would have been nice if someone could test on other controller as well. But >>> another instance of dwc3 is also very welcome. >>>> It's quite possible, please test on your side. >>>> We are happy to test any fixes if you come up with. >> >> -- >> With Best Regards, >> Andy Shevchenko >> >>
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