On Tue, Jun 01, 2021 at 09:51:56AM -0500, Alex Villacís Lasso wrote:

Here is the full result of the test I performed. First I installed the 
distro kernel update, kernel-5.12.8-300.fc34.x86_64, then rebooted. 
Anything with a date is the journalctl output. Everything else is 
console input and output. I have pasted the relevant journalctl messages 
immediately after the command or action that triggered them.

$ miniterm.py /dev/ttyUSB0 115200
Traceback (most recent call last):
   File "/usr/bin/miniterm.py", line 976, in <module>
     main()
   File "/usr/bin/miniterm.py", line 932, in main
     serial_instance.open()
   File "/usr/lib/python3.9/site-packages/serial/serialposix.py", line 
288, in open
     self._update_rts_state()
   File "/usr/lib/python3.9/site-packages/serial/serialposix.py", line 
627, in _update_rts_state
     fcntl.ioctl(self.fd, TIOCMBIS, TIOCM_RTS_str)
BrokenPipeError: [Errno 32] Broken pipe

jun 01 09:23:43 karlalex-asus systemd[1665]: Started VTE child process 
3306 launched by gnome-terminal-server process 2856.
jun 01 09:23:55 karlalex-asus kernel: cp210x ttyUSB0: 
cp210x_change_speed - setting baud rate to 9600
jun 01 09:23:55 karlalex-asus kernel: cp210x ttyUSB0: 
cp210x_set_flow_control - ctrl = 0x00, flow = 0x01
jun 01 09:23:55 karlalex-asus kernel: cp210x ttyUSB0: 
cp210x_tiocmset_port - control = 0x0303
jun 01 09:23:55 karlalex-asus kernel: cp210x ttyUSB0: failed set request 
0x7 status: -32
jun 01 09:23:55 karlalex-asus kernel: cp210x ttyUSB0: 
cp210x_change_speed - setting baud rate to 115384
jun 01 09:23:55 karlalex-asus kernel: cp210x ttyUSB0: 
cp210x_set_flow_control - ctrl = 0x01, flow = 0x40
jun 01 09:23:55 karlalex-asus kernel: cp210x ttyUSB0: 
cp210x_tiocmset_port - control = 0x0101
jun 01 09:23:55 karlalex-asus kernel: cp210x ttyUSB0: 
cp210x_tiocmset_port - control = 0x0202
jun 01 09:23:55 karlalex-asus kernel: cp210x ttyUSB0: failed set request 
0x7 status: -32
jun 01 09:23:55 karlalex-asus python3[3362]: detected unhandled Python 
exception in '/usr/bin/miniterm.py'
jun 01 09:23:55 karlalex-asus kernel: cp210x ttyUSB0: 
cp210x_tiocmset_port - control = 0x0300
jun 01 09:23:55 karlalex-asus kernel: cp210x ttyUSB0: failed set request 
0x7 status: -32

Thanks a lot for this.

Could you try applying the below patch, and with debugging enabled

	1. plug the device in
	2. start the terminal program 

and then send me the logs?

This should show the current device settings which appear to have flow
control enabled (which the driver fails to disable).

I note that the mere act of running stty -a on the device also triggers 
the error.

Yeah, you'll see this error on every open/close when the driver tries to
assert/deassert RTS.

Johan


From 736c4c099591317d55a20da627db3b148d8d71ca Mon Sep 17 00:00:00 2001
From: Johan Hovold <johan@kernel.org>
Date: Tue, 1 Jun 2021 17:29:01 +0200
Subject: [PATCH] USB: cp210x: add flow-control debugging

Signed-off-by: Johan Hovold <johan@kernel.org>
---
 drivers/usb/serial/cp210x.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/usb/serial/cp210x.c b/drivers/usb/serial/cp210x.c
index ee595d1bea0a..92382798b574 100644
--- a/drivers/usb/serial/cp210x.c
+++ b/drivers/usb/serial/cp210x.c

@@ -1159,6 +1159,12 @@ static void cp210x_set_flow_control(struct tty_struct *tty,
 	ctl_hs = le32_to_cpu(flow_ctl.ulControlHandshake);
 	flow_repl = le32_to_cpu(flow_ctl.ulFlowReplace);
 
+	dev_dbg(&port->dev, "%s - ctrl = 0x%02x, flow = 0x%02x\n", __func__,
+			ctl_hs, flow_repl);
+	dev_dbg(&port->dev, "%s - xon_limit = %u, xoff_limit = %u\n", __func__,
+			le32_to_cpu(flow_ctl.ulXonLimit),
+			le32_to_cpu(flow_ctl.ulXoffLimit));
+
 	ctl_hs &= ~CP210X_SERIAL_DSR_HANDSHAKE;
 	ctl_hs &= ~CP210X_SERIAL_DCD_HANDSHAKE;
 	ctl_hs &= ~CP210X_SERIAL_DSR_SENSITIVITY;

-- 
2.31.1