On Sat, Jul 17, 2021 at 07:21:37PM +0000, bugzilla-daemon@bugzilla.kernel.org wrote:
> https://bugzilla.kernel.org/show_bug.cgi?id=213771
> 
>             Bug ID: 213771
>            Summary: ch341 USB-Serial converter receives but does not send
>            Product: Drivers
>            Version: 2.5
>     Kernel Version: 5.12-rc3
>           Hardware: All
>                 OS: Linux
>               Tree: Mainline
>             Status: NEW
>           Severity: normal
>           Priority: P1
>          Component: USB
>           Assignee: drivers_usb@kernel-bugs.kernel.org
>           Reporter: luzemario@gmail.com
>         Regression: No
> 
> Please see Ubuntu bug
> https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1919051.
> 
> Tested with Alpine Linux alpine 5.10.16-0-lts kernel too.
> 
> Possibly still exists in the latest (5.14) kernel.

Please provide some more details to make this report self-contained
(i.e. don't just add a link to another bug tracker).

Also, has this device ever worked with Linux and if so which version?

Johan

Sorry. Description was copied from former bugtracker to make it self-conteined. Iw was tested within Ubuntu and Alpine, with Linuz original kernel. Please ignore Ubuntu-specific information.

*********

This device works flawlessly on Windows XP with native driver, both as a physical machine or inside a VM. It appears on XP's device management as "USB 2.0" name.

On Ubuntu, Shorting pins 2 and 3 of DB9 connector does not give back characters sent (no echo), nor typed strings are sent to other RS232 devices, despite of communication settings. Characters from remote devices are correctly received. Using a null modem cable to other RS232 terminal shows that the local terminal receives, but does not transmit.

Its worth to mention: passing through the device to a guest virtual machine (KVM) running Windows XP makes it work correctly with XP driver inside the guest OS. Bringing back the device stops transmitting. Only receive works.

Tested with the version below:
NAME="Ubuntu"
VERSION="20.04.2 LTS (Focal Fossa)"
ID=ubuntu
ID_LIKE=debian
PRETTY_NAME="Ubuntu 20.04.2 LTS"
VERSION_ID="20.04"
HOME_URL="https://www.ubuntu.com/"
SUPPORT_URL="https://help.ubuntu.com/"
BUG_REPORT_URL="https://bugs.launchpad.net/ubuntu/"
PRIVACY_POLICY_URL="https://www.ubuntu.com/legal/terms-and-policies/privacy-policy"
VERSION_CODENAME=focal
UBUNTU_CODENAME=focal

Kernel:
Linux host 5.4.0-66-generic #74-Ubuntu SMP Wed Jan 27 22:54:38 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux

Device ID:
ID 4348:5523 WinChipHead USB->RS 232 adapter with Prolifec PL 2303 chipset

Modinfo:
filename: /lib/modules/5.4.0-66-generic/kernel/drivers/usb/serial/ch341.ko
license: GPL v2
srcversion: 8F5F64E72BDA4E76E6F4F4D
alias: usb:v4348p5523d*dc*dsc*dp*ic*isc*ip*in*
alias: usb:v1A86p7523d*dc*dsc*dp*ic*isc*ip*in*
alias: usb:v1A86p7522d*dc*dsc*dp*ic*isc*ip*in*
alias: usb:v1A86p5523d*dc*dsc*dp*ic*isc*ip*in*
alias: usb:v1A86p5512d*dc*dsc*dp*ic*isc*ip*in*
depends: usbserial
retpoline: Y
intree: Y
name: ch341
vermagic: 5.4.0-66-generic SMP mod_unload
sig_id: PKCS#7
signer: Build time autogenerated kernel key
sig_key: 1E:07:0D:94:23:77:98:99:05:31:F3:76:E8:6B:76:12:7C:83:9E:05
sig_hashalgo: sha512
signature: 50:CE:79:92:87:EA:82:77:A9:25:A3:B7:F2:B3:ED:63:FE:85:EB:61:
                7A:31:C5:9E:E5:78:E5:44:C6:FE:5D:74:4A:60:B6:0A:94:3F:C3:70:
                0B:6D:27:A6:89:F7:D2:AC:8E:71:AC:0D:AF:5D:3A:19:07:18:F9:7C:
                B8:3C:47:DF:18:4D:13:C9:F8:45:AC:81:19:B0:DE:57:16:1A:F5:C6:
                AC:41:7E:E7:F2:6D:29:9C:14:A3:04:F8:9B:DF:8D:2E:9F:34:44:18:
                A8:FF:C6:A4:AF:04:86:D5:6D:F2:4C:AD:D2:65:4C:63:0F:C1:82:E3:
                28:20:F2:D4:80:86:1A:67:1D:A2:56:18:87:E2:AB:40:E6:6A:48:E5:
                D7:D2:6F:6F:DB:05:20:B2:76:81:5C:0C:36:02:37:E9:A2:08:4E:53:
                5E:9C:18:03:50:11:2D:E4:62:74:6E:CB:42:67:25:22:0C:F6:55:D8:
                6F:E3:5A:15:AC:10:B7:F2:B7:C9:20:6C:19:ED:CC:7D:CC:CB:48:3B:
                B0:5E:E3:ED:05:DF:DF:65:FF:19:AD:76:6E:40:D2:0B:F0:11:65:D5:
                92:7D:C9:3A:32:BE:A8:13:CE:C1:DE:D9:73:0F:0A:0B:8A:08:55:2E:
                41:9D:B9:9A:AD:EC:4C:7D:98:3A:52:38:DF:78:DE:33:F1:14:A2:1B:
                AC:93:FD:30:76:A5:7C:AF:13:16:B8:5E:0B:73:A7:1F:20:E4:54:44:
                07:A2:11:7F:D7:0E:B3:1C:A9:AA:73:76:0E:89:E0:D5:74:39:66:2F:
                E8:14:93:EC:7A:B2:23:E0:CC:77:9F:CD:D9:99:CB:B0:14:21:1C:1F:
                0C:E9:30:B8:C3:55:8F:49:FC:88:5D:EF:20:B9:0E:F2:88:28:5A:93:
                08:4D:2B:76:64:85:D1:E0:1C:9C:4B:86:2C:DB:65:F6:D8:23:A0:8D:
                1B:22:74:0C:B9:41:9E:57:5A:67:4C:CC:1F:E2:43:5F:C2:21:82:E6:
                D4:C1:66:6F:30:54:27:2E:1D:22:8C:65:7F:93:C8:1D:C0:51:F0:7D:
                7A:96:3A:3B:3D:C4:6E:69:DF:83:8A:85:0D:35:15:F9:5E:89:0F:D5:
                9E:6F:A1:5F:39:CE:2A:88:57:97:DF:42:5C:70:12:4E:91:9E:1A:92:
                49:99:C3:7B:38:12:B0:3A:D0:92:38:45:C7:74:3C:66:0F:A1:9C:C2:
                9F:DC:A2:1B:DF:20:BB:F5:A5:F0:10:D6:6F:4F:C1:90:00:C3:F9:D8:
                42:96:D2:28:FD:DE:21:33:6C:F4:7F:18:B2:ED:F9:A6:A4:4A:A5:4F:
                26:7C:C0:F7:8B:A9:B3:2F:5A:5B:E2:B8

Demsg entries:
usb 4-3: new full-speed USB device number 6 using ohci-pci
usb 4-3: New USB device found, idVendor=4348, idProduct=5523, bcdDevice= 2.50
usb 4-3: New USB device strings: Mfr=0, Product=0, SerialNumber=0
ch341 4-3:1.0: ch341-uart converter detected
usb 4-3: ch341-uart converter now attached to ttyUSB0
---
ProblemType: Bug
ApportVersion: 2.20.11-0ubuntu27.16
Architecture: amd64
[...] # not relevant / stripped
DistroRelease: Ubuntu 20.04
InstallationDate: Installed on 2021-01-23 (50 days ago)
InstallationMedia: Kubuntu 20.04.1 LTS "Focal Fossa" - Release amd64 (20200731)
MachineType: System manufacturer System Product Name
NonfreeKernelModules: nvidia_modeset nvidia
Package: linux (not installed)
ProcFB: 0 VESA VGA
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-5.4.0-66-generic root=UUID=68929bb0-3af4-4634-8d5b-c2846910c077 ro locale=pt_BR quiet splash vt.handoff=7
ProcVersionSignature: Ubuntu 5.4.0-66.74-generic 5.4.86
RelatedPackageVersions:
 linux-restricted-modules-5.4.0-66-generic N/A
 linux-backports-modules-5.4.0-66-generic N/A
 linux-firmware 1.187.10
RfKill:

Tags: focal
Uname: Linux 5.4.0-66-generic x86_64
UpgradeStatus: No upgrade log present (probably fresh install)
UserGroups: adm cdrom dip libvirt lpadmin lxd plugdev sambashare sudo
_MarkForUpload: True
dmi.bios.date: 11/18/2016
dmi.bios.vendor: American Megatrends Inc.
dmi.bios.version: 0502
dmi.board.asset.tag: To Be Filled By O.E.M.
dmi.board.name: M5A78L-M PLUS/USB3
dmi.board.vendor: ASUSTeK Computer INC.
dmi.board.version: Rev X.0x
dmi.chassis.asset.tag: Asset-1234567890
dmi.chassis.type: 3
dmi.chassis.vendor: Chassis Manufacture
dmi.chassis.version: Chassis Version
dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvr0502:bd11/18/2016:svnSystemmanufacturer:pnSystemProductName:pvrSystemVersion:rvnASUSTeKComputerINC.:rnM5A78L-MPLUS/USB3:rvrRevX.0x:cvnChassisManufacture:ct3:cvrChassisVersion:
dmi.product.family: To Be Filled By O.E.M.
dmi.product.name: System Product Name
dmi.product.sku: To Be Filled By O.E.M.
dmi.product.version: System Version
dmi.sys.vendor: System manufacturer

I do not know if the device worked before. I did not test with earlier kernel versions.

If you guess any early versions known to work, please tell me, and I will try to test the version requested.

On Wed, Jul 21, 2021 at 07:00:08PM +0000, bugzilla-daemon@bugzilla.kernel.org wrote:

> On Ubuntu, Shorting pins 2 and 3 of DB9 connector does not give back
> characters
> sent (no echo), nor typed strings are sent to other RS232 devices, despite of
> communication settings. Characters from remote devices are correctly
> received.
> Using a null modem cable to other RS232 terminal shows that the local
> terminal
> receives, but does not transmit.

What happens if you also short RTS and CTS?

And are you able to change the baud rate at all?

> Kernel:
> Linux host 5.4.0-66-generic #74-Ubuntu SMP Wed Jan 27 22:54:38 UTC 2021
> x86_64
> x86_64 x86_64 GNU/Linux

Please confirm using a recent mainline kernel (e.g. 5.13).

> Device ID:
> ID 4348:5523 WinChipHead USB->RS 232 adapter with Prolifec PL 2303 chipset

This looks strange. I don't think these devices are based on
(misspelled) Prolific PL2303 chips.

This is possibly some kind of counterfeit device. You could try using
the pl2303 driver.

Please also post the output of lsusb -v.

Hi,
This version probably has the same or similar problem:

Linux home 5.11.0-37-generic #41~20.04.2-Ubuntu

On Sat, Oct 09, 2021 at 08:07:00PM +0000, bugzilla-daemon@bugzilla.kernel.org wrote:

> --- Comment #5 from Denis Bondar (bondar.den@gmail.com) ---
> Hi,
> This version probably has the same or similar problem:
> 
> Linux home 5.11.0-37-generic #41~20.04.2-Ubuntu

That's also not a mainline kernel. Unless you can reproduce this with a
mainline (or stable) kernel, you need to report this to Ubuntu.

Providing answers to the questions I asked the original reporter might
help too.

Johan

(In reply to Johan Hovold from comment #6)
> On Sat, Oct 09, 2021 at 08:07:00PM +0000,
> bugzilla-daemon@bugzilla.kernel.org wrote:
> 
> That's also not a mainline kernel. Unless you can reproduce this with a
> mainline (or stable) kernel, you need to report this to Ubuntu.
> 
> Providing answers to the questions I asked the original reporter might
> help too.
> 
> Johan

Thank you very much. Sorry for the inconvenience.