Date: Thu, 30 May 2024 21:06:47 +0200
From: Ferry Toth <fntoth@...il.com>
To: Hardik Gajjar <hgajjar@...adit-jv.com>
Cc: 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, regressions@...mhuis.info
Subject: Re: [PATCH v4] usb: gadget: u_ether: Replace netif_stop_queue with
 netif_device_detach

Hi,

Op 28-05-2024 om 09:18 schreef Hardik Gajjar:
> On Sun, May 26, 2024 at 10:52:53PM +0200, Ferry Toth wrote:
>> Hi
>>
>> Op 15-05-2024 om 20:38 schreef Ferry Toth:
>>> Hi,
>>>
>>> Sorry to have kept you waiting, I was away for a short break.
>>>
>>> Patch tested below.
>>>
>>> Op 10-05-2024 om 11:45 schreef Hardik Gajjar:
>>>> On Thu, May 02, 2024 at 10:32:16PM +0200, Ferry Toth wrote:
>>>>> Oops, sorry, wrong file attached . Now correct one.
>>>>>
>>>>> Op 02-05-2024 om 22:13 schreef Ferry Toth:
>>>>>> Op 02-05-2024 om 17:29 schreef Hardik Gajjar:
>>>>>>> On Tue, Apr 30, 2024 at 11:12:17PM +0200, Ferry Toth wrote:
>>>>>>>> Hi,
>>>>>>>>
>>>>>>>> Op 30-04-2024 om 21:40 schreef Ferry Toth:
>>>>>>>>> Hi,
>>>>>>>>>
>>>>>>>>> Op 30-04-2024 om 17:32 schreef Hardik Gajjar:
>>>>>>>>>> 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() ?
>>>>>>>>>
>>>>>>>>> Nope. It's a pitty that the trace formatting got messed up
>>>>>>>>> above. But as
>>>>>>>>> you can see I traced gether_* and eem_*. After eem_unbind no traced
>>>>>>>>> function is called, until I flip the switch to device mode.
>>>>>>>>> The ... at the end is where I cut uninteresting eem_unwrap
>>>>>>>>> <-rx_complete
>>>>>>>>> and eem_wrap <-eth_start_xmit lines.
>>>>>>>>>
>>>>>>>>>> If not then, you may try to enable tracing of TCP/IP stack and
>>>>>>>>>> network side to check who deleting the sysfs entry
>>>>>>>>>
>>>>>>>>> Yes, that's a vast amount of functions to trace. And I don't see how
>>>>>>>>> that would be related to the patch we're
>>>>>>>>> discussing here. I was hoping
>>>>>>>>> for a little more targeted hint.
>>>>>>>>
>>>>>>>> Now filtering 'gether_*', 'eem_*', '*configfs_*', 'composite_*',
>>>>>>>> 'usb_fun*',
>>>>>>>> 'reset_config' and 'device_remove_file' leads me to:
>>>>>>>>
>>>>>>>> TIMESTAMP  FUNCTION
>>>>>>>>       |         |
>>>>>>>>      49.952477: eem_wrap <-eth_start_xmit
>>>>>>>>      55.072455: eem_wrap <-eth_start_xmit
>>>>>>>>      55.072621: eem_unwrap <-rx_complete
>>>>>>>>      59.011540: configfs_composite_reset <-usb_gadget_udc_reset
>>>>>>>>      59.011545: composite_reset <-configfs_composite_reset
>>>>>>>>      59.011548: reset_config <-__composite_disconnect
>>>>>>>>      59.013565: eem_disable <-reset_config
>>>>>>>>      59.013567: gether_disconnect <-reset_config
>>>>>>>>      59.049560: device_remove_file <-device_remove
>>>>>>>>      59.051185: configfs_composite_disconnect <-usb_gadget_disco
>>>>>>>>      59.051189: composite_disconnect <-configfs_composite_discon
>>>>>>>>      59.051195: configfs_composite_unbind <-gadget_unbind_driver
>>>>>>>>      59.052519: eem_unbind <-purge_configs_funcs
>>>>>>>>      59.052529: composite_dev_cleanup <-configfs_composite_unbin
>>>>>>>>      59.052537: device_remove_file <-composite_dev_cleanup
>>>>>>>>
>>>>>>>> device_remove_file gets called twice, once by device_remove after
>>>>>>>> gether_disconnect (that the one). The 2nd time by
>>>>>>>> composite_dev_cleanup
>>>>>>>> (removing the gadget)
>>>>>>>
>>>>>>> I believe that the device_remove_file function is only removing
>>>>>>> suspend-specific attributes, not the complete gadget.
>>>>>>> Typically, when you perform the role switch, the Gadget start/stop
>>>>>>> function in your UDC driver is called. These functions should not
>>>>>>> delete the gadget
>>>>>>>
>>>>>>> To investigate further, could you please enable the DWC3 functions
>>>>>>> in ftrace and check who is removing the gadget?
>>>>>>> I can also enable this on my system and compare the logs with yours,
>>>>>>> but I will be in PI planning for 1.5 weeks and may not be able to
>>>>>>> provide immediate support.
>>>>>>
>>>>>> Yes, but of course adding dwc3_* (and usb_*) also traces host mode, so
>>>>>> trace is 600kb. I cut uninteresting stuff before
>>>>>> configfs_composite_reset <-usb_gadget_udc_reset and after
>>>>>> __dwc3_set_mode, <https://urldefense.proofpoint.com/v2/url?u=http-3A__300linesremain.Seeattachedtar.gzforyouto&d=DwIDaQ&c=euGZstcaTDllvimEN8b7jXrwqOf-v5A_CdpgnVfiiMM&r=SAhjP5GOmrADp1v_EE5jWoSuMlYCIt9gKduw-DCBPLs&m=zdiBhk-2V5AXxu707QAhbCgWR4qNVRARBmxN17nVB69gVOm-QPqrJeKpo4_trszw&s=ixagWKgLs6wQDJfwh4vIDQNDiy8GZnK9KnUELIfiJz0&e=>
>>>>>> compare.
>>>>>>
>>>> Could you please try with the following patch and see if your issue
>>>> resolves ?
>>>>
>>>> diff --git a/drivers/usb/gadget/function/f_eem.c
>>>> b/drivers/usb/gadget/function/f_eem.c
>>>> index 3b445bd88498..c2a904475083 100644
>>>> --- a/drivers/usb/gadget/function/f_eem.c
>>>> +++ b/drivers/usb/gadget/function/f_eem.c
>>>> @@ -247,7 +247,7 @@ static int eem_bind(struct usb_configuration *c,
>>>> struct usb_function *f)
>>>>        struct usb_composite_dev *cdev = c->cdev;
>>>>        struct f_eem        *eem = func_to_eem(f);
>>>>        struct usb_string    *us;
>>>> -    int            status;
>>>> +    int            status = 0;
>>>>        struct usb_ep        *ep;
>>>>        struct f_eem_opts    *eem_opts;
>>>> @@ -260,16 +260,20 @@ static int eem_bind(struct usb_configuration
>>>> *c, struct usb_function *f)
>>>>         * with list_for_each_entry, so we assume no race condition
>>>>         * with regard to eem_opts->bound access
>>>>         */
>>>> +    mutex_lock(&eem_opts->lock);
>>>> +    gether_set_gadget(eem_opts->net, cdev->gadget);
>>>> +
>>>>        if (!eem_opts->bound) {
>>>> -        mutex_lock(&eem_opts->lock);
>>>> -        gether_set_gadget(eem_opts->net, cdev->gadget);
>>>>            status = gether_register_netdev(eem_opts->net);
>>>> -        mutex_unlock(&eem_opts->lock);
>>>> -        if (status)
>>>> -            return status;
>>>> -        eem_opts->bound = true;
>>>>        }
>>>> +    mutex_unlock(&eem_opts->lock);
>>>> +
>>>> +    if (status)
>>>> +        goto fail;
>>>> +
>>>> +    eem_opts->bound = true;
>>>> +
>>>>        us = usb_gstrings_attach(cdev, eem_strings,
>>>>                     ARRAY_SIZE(eem_string_defs));
>>>>
>>>
>>> After switching from host -> device -> host the usb0 device as seen by
>>> ifconfig remains "RUNNING" and in the routing table.
>>>
>>> FYI This is the regression.
>>
>> For us, I don't see any advantages in having this patch and only the
>> downside. Do you have any further ideas / patches that we could test.
>>
>> Otherwise, it might be best to go with the original suggestion and revert
>> until it gets sorted out?
> 
> Hello,
> 
> Okay, lets revert the patch till we fix your problem. Would you be able to send the revert ? or shall I ?
> 
> However, We are very much intrested to fix your problem and upstream the v2.
> Therefore could you please share the following details to reproduce the issue

Instruction to establish the eem connection on the device (connman) and 
the host (networkmanager) here:
https://edison-fw.github.io/meta-intel-edison/4.2-networking.html#gadget

> - How did you created the gadget ? Could you please share the exact commands to create the eem gadget ?

Sure, you can find the u-dev rules and the script here on GH:
https://github.com/edison-fw/meta-intel-edison/tree/kirkstone/meta-intel-edison-bsp/recipes-support/gadget/files

> - Arch of your test bench (arm, x86)

This is x86_64 although we can just as easily build i686 if needed.

> - How the DWC3 controller connected to your system ? via PCIe slot ? Could you please share the part number of the PCIe card ?

Like Andy mentioned it is in the SOC. It's described in ACPI (in U-Boot 
together with other SOC level devices) here:
https://github.com/u-boot/u-boot/blob/ea722aa5eb33740ae77e8816aeb72b385e621cd0/arch/x86/include/asm/arch-tangier/acpi/southcluster.asl#L333

> Hardik
> 
>>
>>> Also /sys/devices/pci0000:00/0000:00:11.0/dwc3.0.auto/gadget.0/net is
>>> still missing.
>>>
>>> After deeper diving into v6.1.0, I found the latter a longer existing
>>> bug, not caused by your patch.
>>>
>>> More over, this doesn't seem to do any harm.
>>>
>>> The first issue does, as we try to route traffic over a device that no
>>> longer exists.
>>>
>>>>>>> Additionally, please check if you have any customized DWC patches
>>>>>>> that may be causing this problem.
>>>>>>>
>>>>>>>>
>>>>>>>>> You may recall the whole issue did not occur before this
>>>>>>>>> patch got applied.
>>>>>>>>>
>>>>>>>>>> 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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