Am 24.03.23 um 13:35 schrieb Ilpo Järvinen:
On Fri, 24 Mar 2023, Francesco Dolcini wrote:
Hello
On Fri, Mar 24, 2023 at 01:47:59PM +0200, Ilpo Järvinen wrote:
On Fri, 24 Mar 2023, Stefan Wahren wrote:
after switching to Linux 6.1.21 on our Tarragon board (i.MX6ULL SoC), we
experience the following issues with the debug UART (115200 baud, 8N1, no
hardware flow control):
- overrun errors if we paste in multiple text lines while system is idle
- no reaction to single key strokes while system is on higher load
After reverting 7a637784d517 ("serial: imx: reduce RX interrupt frequency")
the issue disappear.
Maybe it's worth to mention that the Tarragon board uses two additional
application UARTs with similiar baud rates (9600 - 115200 baud, no hardware
flow control) for RS485 communication, but there are no overrun errors (with
and without the mention change).
This has come up earlier, see e.g.:
https://lore.kernel.org/linux-serial/20221003110850.GA28338@xxxxxxxxxxxxxxxxxxxxxxxxxxxx/
yep, it looks exactly the same issue.
We did not verify if this was affecting other UARTs. However, isn't RS485
half-duplex?
While half-duplex is more likely by far due simplicity, RS485 could also
be full-duplex. It seems imx driver supports for both modes.
The RS485 on Tarragon is half-duplex, but this is implemented in
external hardware. So from Linux / driver point of view it's a RS232.
To us the current behavior (overrun errors and no reaction under load)
is not acceptable. I agree that increasing the rx threshold isn't the
real issue. But i needed a starting point for a discussion.
So any ideas how to investigate this further are welcome.
