imx6UL: permanent serial reception of FF char with parity error.

[jean-françoistr]

Hello,
I have a serial communication at 2400 baud 8 Bits parity even of poor quality, and I receive a lot of parity errors. After an undetermined number of parity errors, the processor starts giving without stopping the FF char, with a parity error.
The input hardware signals are at rest. It is as if the receive interrupt flag never returns to 0.

Monitor in function "imx_rxint" of file imx.c

OS: Linux 4.14.218
µP : is an imx6ULL
Have you ever encountered this problem?
What can I do to stop it?

Thank you for your help.

[jamesbone]

Did you try to deactivate DEBUG_SERIAL? If the baud rate of your debug output is slow this may cause the errors.

[jean-françoistr]

Hello Jamesbone,
Thank you for your response.

The debug is already disabled in the kernel. Here is the lines of .Config Kernel.

Is there another DEBUG to deactivate ?

[jamesbone]

Do you think you can share some of the code? are you using flow control? becaue in the i.MX6UL there is no signal of flow control in the uart.

[jean-françoistr · Accepted solution]

Hello,

Thank you for your response.
No, I don't use flow control.

I have made progress on understanding and solving the problem.
My communication has a lot of parity error but also the reception of break error.
Here is the result of the ioctl command with the parameter "TIOCGICOUNT".

I think µP has a problem under these particular conditions.
Here's the solution I've implemented is one that works. When the number of errors reaches a threshold I do a software reset using the "UCR2_SRST" bit. In the "Part-of_imx.c" file the part of code added.
I have proof that it takes the µP out of this permanent FF sending state in the file "TheProof.txt"

do you think this is the right solution ?

Jean-françois

[jean-françoistr]

Hello JamesBone,
Yes, this software solution fixes the problem.