From: Pali Rohár pali@kernel.org
commit 027b57170bf8bb6999a28e4a5f3d78bf1db0f90c upstream.
Since commit edc6afc54968 ("tty: switch to ktermios and new framework") termios speed is no longer stored only in c_cflag member but also in new additional c_ispeed and c_ospeed members. If BOTHER flag is set in c_cflag then termios speed is stored only in these new members.
Therefore to correctly restore termios speed it is required to store also ispeed and ospeed members, not only cflag member.
In case only cflag member with BOTHER flag is restored then functions tty_termios_baud_rate() and tty_termios_input_baud_rate() returns baudrate stored in c_ospeed / c_ispeed member, which is zero as it was not restored too. If reported baudrate is invalid (e.g. zero) then serial core functions report fallback baudrate value 9600. So it means that in this case original baudrate is lost and kernel changes it to value 9600.
Simple reproducer of this issue is to boot kernel with following command line argument: "console=ttyXXX,86400" (where ttyXXX is the device name). For speed 86400 there is no Bnnn constant and therefore kernel has to represent this speed via BOTHER c_cflag. Which means that speed is stored only in c_ospeed and c_ispeed members, not in c_cflag anymore.
If bootloader correctly configures serial device to speed 86400 then kernel prints boot log to early console at speed speed 86400 without any issue. But after kernel starts initializing real console device ttyXXX then speed is changed to fallback value 9600 because information about speed was lost.
This patch fixes above issue by storing and restoring also ispeed and ospeed members, which are required for BOTHER flag.
Fixes: edc6afc54968 ("[PATCH] tty: switch to ktermios and new framework") Cc: stable@vger.kernel.org Signed-off-by: Pali Rohár pali@kernel.org Link: https://lore.kernel.org/r/20211002130900.9518-1-pali@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/tty/serial/serial_core.c | 16 ++++++++++++++-- include/linux/console.h | 2 ++ 2 files changed, 16 insertions(+), 2 deletions(-)
--- a/drivers/tty/serial/serial_core.c +++ b/drivers/tty/serial/serial_core.c @@ -219,7 +219,11 @@ static int uart_port_startup(struct tty_ if (retval == 0) { if (uart_console(uport) && uport->cons->cflag) { tty->termios.c_cflag = uport->cons->cflag; + tty->termios.c_ispeed = uport->cons->ispeed; + tty->termios.c_ospeed = uport->cons->ospeed; uport->cons->cflag = 0; + uport->cons->ispeed = 0; + uport->cons->ospeed = 0; } /* * Initialise the hardware port settings. @@ -287,8 +291,11 @@ static void uart_shutdown(struct tty_str /* * Turn off DTR and RTS early. */ - if (uport && uart_console(uport) && tty) + if (uport && uart_console(uport) && tty) { uport->cons->cflag = tty->termios.c_cflag; + uport->cons->ispeed = tty->termios.c_ispeed; + uport->cons->ospeed = tty->termios.c_ospeed; + }
if (!tty || C_HUPCL(tty)) uart_port_dtr_rts(uport, 0); @@ -2062,8 +2069,11 @@ uart_set_options(struct uart_port *port, * Allow the setting of the UART parameters with a NULL console * too: */ - if (co) + if (co) { co->cflag = termios.c_cflag; + co->ispeed = termios.c_ispeed; + co->ospeed = termios.c_ospeed; + }
return 0; } @@ -2197,6 +2207,8 @@ int uart_resume_port(struct uart_driver */ memset(&termios, 0, sizeof(struct ktermios)); termios.c_cflag = uport->cons->cflag; + termios.c_ispeed = uport->cons->ispeed; + termios.c_ospeed = uport->cons->ospeed;
/* * If that's unset, use the tty termios setting. --- a/include/linux/console.h +++ b/include/linux/console.h @@ -153,6 +153,8 @@ struct console { short flags; short index; int cflag; + uint ispeed; + uint ospeed; void *data; struct console *next; };