This is a note to let you know that I've just added the patch titled
serial: atmel: fix incorrect baudrate setup
to the 6.1-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
serial-atmel-fix-incorrect-baudrate-setup.patch
and it can be found in the queue-6.1 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 5bfdd3c654bd879bff50c2e85e42f85ae698b42f Mon Sep 17 00:00:00 2001
From: Tobias Schramm <t.schramm@xxxxxxxxxxx>
Date: Mon, 9 Jan 2023 08:29:40 +0100
Subject: serial: atmel: fix incorrect baudrate setup
From: Tobias Schramm <t.schramm@xxxxxxxxxxx>
commit 5bfdd3c654bd879bff50c2e85e42f85ae698b42f upstream.
Commit ba47f97a18f2 ("serial: core: remove baud_rates when serial console
setup") changed uart_set_options to select the correct baudrate
configuration based on the absolute error between requested baudrate and
available standard baudrate settings.
Prior to that commit the baudrate was selected based on which predefined
standard baudrate did not exceed the requested baudrate.
This change of selection logic was never reflected in the atmel serial
driver. Thus the comment left in the atmel serial driver is no longer
accurate.
Additionally the manual rounding up described in that comment and applied
via (quot - 1) requests an incorrect baudrate. Since uart_set_options uses
tty_termios_encode_baud_rate to determine the appropriate baudrate flags
this can cause baudrate selection to fail entirely because
tty_termios_encode_baud_rate will only select a baudrate if relative error
between requested and selected baudrate does not exceed +/-2%.
Fix that by requesting actual, exact baudrate used by the serial.
Fixes: ba47f97a18f2 ("serial: core: remove baud_rates when serial console setup")
Cc: stable <stable@xxxxxxxxxx>
Signed-off-by: Tobias Schramm <t.schramm@xxxxxxxxxxx>
Acked-by: Richard Genoud <richard.genoud@xxxxxxxxx>
Link: https://lore.kernel.org/r/20230109072940.202936-1-t.schramm@xxxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/tty/serial/atmel_serial.c | 8 +-------
1 file changed, 1 insertion(+), 7 deletions(-)
--- a/drivers/tty/serial/atmel_serial.c
+++ b/drivers/tty/serial/atmel_serial.c
@@ -2673,13 +2673,7 @@ static void __init atmel_console_get_opt
else if (mr == ATMEL_US_PAR_ODD)
*parity = 'o';
- /*
- * The serial core only rounds down when matching this to a
- * supported baud rate. Make sure we don't end up slightly
- * lower than one of those, as it would make us fall through
- * to a much lower baud rate than we really want.
- */
- *baud = port->uartclk / (16 * (quot - 1));
+ *baud = port->uartclk / (16 * quot);
}
static int __init atmel_console_setup(struct console *co, char *options)
Patches currently in stable-queue which might be from t.schramm@xxxxxxxxxxx are
queue-6.1/serial-atmel-fix-incorrect-baudrate-setup.patch
