Date: Wed, 26 Aug 2015 19:04:40 +0200
From: Johan Hovold <johan@kernel.org>
To: Ajay Garg <ajaygargnsit@gmail.com>
Cc: linux-kernel@vger.kernel.org, linux-usb@vger.kernel.org
Subject: Re: Likely issue with ch341 kernel-module/driver
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[ +CC: linux-usb ]

On Wed, Aug 26, 2015 at 09:39:36PM +0530, Ajay Garg wrote:
> Hi all.
> 
> I am attaching the RS232-TTL via a serial-USB converter on my machine.
> 
> However, when I connect a putty-session with my embedded-device, I see
> strange issues (garbage characters transmitted from embedded-device to
> putty; nothing can be read from putty into embedded-device).
> 
> It seems that there is some issue with the driver.

Why do think it's a driver issue?

> Lots of these lines are seen in dmesg ::
> 
> 
> ########################################################################################
> [ 8657.022997] ch341-uart ttyUSB0:
> usb_serial_generic_read_bulk_callback - nonzero urb status: -71
> ########################################################################################
> 
> 
> 
> Other informations ::
> 
> ########################################################################################
> ajay@ajay-HP-15-Notebook-PC:~$ lsusb
> Bus 001 Device 002: ID 8087:8001 Intel Corp.
> Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
> Bus 003 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
> Bus 002 Device 003: ID 05c8:036e Cheng Uei Precision Industry Co., Ltd (Foxlink)
> Bus 002 Device 002: ID 0bda:b001 Realtek Semiconductor Corp.
> Bus 002 Device 011: ID 1a86:7523 QinHeng Electronics HL-340 USB-Serial adapter
> Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
> ########################################################################################
> 
> 
> ########################################################################################
> ajay@ajay-HP-15-Notebook-PC:~$ lsmod | grep ch341
> ch341                  13761  1
> usbserial              38972  3 ch341
> ########################################################################################
> 
> 
> ########################################################################################
> ajay@ajay-HP-15-Notebook-PC:~$ uname -a
> Linux ajay-HP-15-Notebook-PC 3.16.0-30-generic #40~14.04.1-Ubuntu SMP
> Thu Jan 15 17:45:15 UTC 2015 i686 i686 i686 GNU/Linux
> ########################################################################################
> 
> 
> 
> Any chance this can be made to work? Any upgrade that might solve the issue?
> We will be grateful for ideas.

This is a known issue with your device that has been reported in this
thread:

	https://lkml.kernel.org/r/CAF3ayyDe44POd1NoSBqn_gjA8XLoK3r_getDYnWx+a_1rL0r5g@mail.gmail.com

Looks like a hardware issue, I'm afraid.

Johan
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