Bug 214131 - ch341 communication problem
Summary: ch341 communication problem
Status: NEW
Alias: None
Product: Drivers
Classification: Unclassified
Component: USB (show other bugs)
Hardware: All Linux
: P1 normal
Assignee: Default virtual assignee for Drivers/USB
Depends on:
Reported: 2021-08-22 07:11 UTC by Paul Größel
Modified: 2021-09-14 21:47 UTC (History)
3 users (show)

See Also:
Kernel Version: 5.14-rc5
Tree: Mainline
Regression: No

captured communication (73.65 KB, image/png)
2021-08-22 07:11 UTC, Paul Größel
lsusb -v (2.37 KB, text/plain)
2021-08-23 09:14 UTC, Paul Größel

Description Paul Größel 2021-08-22 07:11:49 UTC
Created attachment 298411 [details]
captured communication

Several users reported their USB-Serial Adapter based on ch341 driver does not communicate correctly anymore with kernels somewhere above 5.10.56-1.  

The problem is that flashing an ESP8266 board is not possible anymore with Arduino IDE resulting in a 

"/dev/ttyUSB0 failed to connect: Failed to connect to ESP8266: Timed out waiting for packet header"


I can confirm this issue up to kernel 5.14-rc5. 
Downgrading my kernel to 5.10.52 also solves the problem.

I attached two communication samples from github user jypma.

The issue is was discussed here:
Comment 1 loqs 2021-08-22 23:32:30 UTC
What if you revert 3c18e9baee0ef97510dcda78c82285f52626764b
which was back-ported to 5.10-58 and 5.13.10?

I believe it is the same bug as discussed here https://bugs.archlinux.org/task/71830
Comment 2 Paul Größel 2021-08-23 07:09:22 UTC
Indeed, removing 

.bulk_in_size      = 512,

and recompiling my 5.13.10 kernel solved the issue.
Comment 3 Johan Hovold 2021-08-23 09:07:27 UTC
Thanks for reporting and tracking down the commit that caused the

Could you be a bit more specific about the symptoms here? Judging from a
quick look at the github thread, it appears that the device is still
working although timing may have changes slightly. The arch thread
indicates that the device doesn't even enumerate, which does not seem to
be the case here.

Also please provide the output of "lsusb -v" for this device.
Comment 4 Paul Größel 2021-08-23 09:14:29 UTC
Created attachment 298433 [details]
lsusb -v
Comment 5 Paul Größel 2021-08-23 09:14:49 UTC
I agree, I couldn't find any enumerate related symptoms here:


[ 7572.641499] usb 3-3.4: new full-speed USB device number 7 using xhci_hcd
[ 7572.731906] usb 3-3.4: New USB device found, idVendor=1a86, idProduct=7523, bcdDevice= 2.63
[ 7572.731910] usb 3-3.4: New USB device strings: Mfr=0, Product=2, SerialNumber=0
[ 7572.731912] usb 3-3.4: Product: USB2.0-Serial
[ 7572.788929] ch341 3-3.4:1.0: ch341-uart converter detected
[ 7572.802958] usb 3-3.4: ch341-uart converter now attached to ttyUSB0

lsusb -v see attachment above
Comment 6 Paul Größel 2021-08-23 09:18:26 UTC
Sorry, I have no idea how I could tackle down to more specific symptoms. I do not own a protocol analyzer nor I am a coder.
Comment 7 Johan Hovold 2021-08-24 11:44:23 UTC
On Mon, Aug 23, 2021 at 09:14:49AM +0000, bugzilla-daemon@bugzilla.kernel.org wrote:
> https://bugzilla.kernel.org/show_bug.cgi?id=214131
> --- Comment #5 from Paul Größel (pb.g@gmx.de) ---
> I agree, I couldn't find any enumerate related symptoms here:

I was able to reproduce the problem here. The device doesn't send a
zero-length package in case the received data is a multiple of the
endpoint size so that the bulk transfer doesn't complete (e.g. your
flashing application may not receive replies).

We need to revert the offending commit until we can figure out how to
configure the device to send ZLPs.

Thanks again for reporting this, and sorry about the breakage.

Comment 8 Johan Hovold 2021-08-25 07:21:23 UTC
For the record, I've applied the revert now and it should be backported
to the stable trees shortly:


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