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Message-ID: <20240430153243.GA129136@vmlxhi-118.adit-jv.com> Date: Tue, 30 Apr 2024 17:32:43 +0200 From: Hardik Gajjar <hgajjar@...adit-jv.com> To: Ferry Toth <fntoth@...il.com> CC: Hardik Gajjar <hgajjar@...adit-jv.com>, Andy Shevchenko <andriy.shevchenko@...el.com>, <gregkh@...uxfoundation.org>, <s.hauer@...gutronix.de>, <jonathanh@...dia.com>, <linux-usb@...r.kernel.org>, <linux-kernel@...r.kernel.org>, <quic_linyyuan@...cinc.com>, <paul@...pouillou.net>, <quic_eserrao@...cinc.com>, <erosca@...adit-jv.com> Subject: Re: [PATCH v4] usb: gadget: u_ether: Replace netif_stop_queue with netif_device_detach On Sun, Apr 28, 2024 at 11:07:36PM +0200, Ferry Toth wrote: > Hi, > > Op 25-04-2024 om 23:27 schreef Ferry Toth: > > 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@...a:~# 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@...a:~# 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@...a:~# 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@...a:~# 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@...a:~# 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@...a:~# 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@...a:~# 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(); > > I tried to get a more useful trace: > root@...a:/sys/kernel/tracing# echo 'gether_*' > set_ftrace_filter > root@...a:/sys/kernel/tracing# echo 'eem_*' >> set_ftrace_filter > root@...a:/sys/kernel/tracing# echo function > current_tracer > root@...a:/sys/kernel/tracing# echo 'reset_config' >> set_ftrace_filter > -> switch to host mode then back to device > root@...a:/sys/kernel/tracing# cat trace > # tracer: function > # > # entries-in-buffer/entries-written: 53/53 #P:2 > # > # _-----=> irqs-off/BH-disabled > # / _----=> need-resched > # | / _---=> hardirq/softirq > # || / _--=> preempt-depth > # ||| / _-=> migrate-disable > # |||| / delay > # TASK-PID CPU# ||||| TIMESTAMP FUNCTION > # | | | ||||| | | > irq/68-dwc3-523 [000] D..3. 133.990254: reset_config > <-__composite_disconnect > irq/68-dwc3-523 [000] D..3. 133.992274: eem_disable > <-reset_config > irq/68-dwc3-523 [000] D..3. 133.992276: gether_disconnect > <-reset_config > kworker/1:3-443 [001] ...1. 134.022453: eem_unbind > <-purge_configs_funcs > > -> to device mode > > kworker/1:3-443 [001] ...1. 148.630773: eem_bind > <-usb_add_function > irq/68-dwc3-734 [000] D..3. 149.155209: eem_set_alt > <-composite_setup > irq/68-dwc3-734 [000] D..3. 149.155215: gether_disconnect > <-eem_set_alt > irq/68-dwc3-734 [000] D..3. 149.155220: gether_connect > <-eem_set_alt > irq/68-dwc3-734 [000] D..3. 149.157287: eem_set_alt > <-composite_setup > irq/68-dwc3-734 [000] D..3. 149.157292: gether_disconnect > <-eem_set_alt > irq/68-dwc3-734 [000] D..3. 149.159338: gether_connect > <-eem_set_alt > irq/68-dwc3-734 [000] D..2. 149.239625: eem_unwrap <-rx_complete > ... > > I don't know where to look exactly. Any hints? do you see anything related to gether_cleanup() after eem_unbind() ? If not then, you may try to enable tracing of TCP/IP stack and network side to check who deleting the sysfs entry Hardik > > > > > > 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 don't know what you mean here. Which driver do you mean? > > > > > > > > > > > > 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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