Support for UPF_SPD_* flags is currently broken in more drivers for two
reasons. First one is that uart_update_timeout() function does not
calculate timeout for UPF_SPD_CUST flag correctly. Second reason is that
userspace termios structre is modified by most drivers after each
TIOCSSERIAL or TCSETS call to discard activation of UPF_SPD_* flags.
Reproducer for these issues:
#include <termios.h>
#include <sys/ioctl.h>
#include <asm/ioctls.h>
#include <linux/serial.h>
static unsigned cdiv(unsigned a, unsigned b) {
if (!b) return b;
return (a + (b/2)) / b;
}
void set_active_spd_cust_baud(int fd, unsigned baudrate) {
struct serial_struct serial;
struct termios termios;
tcgetattr(fd, &termios);
ioctl(fd, TIOCGSERIAL, &serial);
serial.flags &= ~ASYNC_SPD_MASK;
serial.flags |= ASYNC_SPD_CUST;
serial.custom_divisor = cdiv(serial.baud_base, baudrate);
ioctl(fd, TIOCSSERIAL, &serial);
cfsetspeed(&termios, B38400);
tcsetattr(fd, TCSANOW, &termios);
}
int is_spd_cust_active(int fd) {
struct serial_struct serial;
struct termios termios;
tcgetattr(fd, &termios);
ioctl(fd, TIOCGSERIAL, &serial);
return
(serial.flags & ASYNC_SPD_MASK) == ASYNC_SPD_CUST &&
cfgetospeed(&termios) == B38400;
}
(error handling was ommited for simplification)
After calling set_active_spd_cust_baud() function SPD custom divisor
should be active and therefore is_spd_cust_active() should return true.
But it is not active (cfgetospeed does not return B38400) and this patch
series should fix it. I have tested it with 8250 driver.
Originally Johan Hovold reported that there may be issue with these
ASYNC_SPD_FLAGS in email:
https://lore.kernel.org/linux-serial/20211007133146.28949-1-johan@xxxxxxxxxx/
Johan, Greg, could you please test these patches if there is not any
regression?
Pali Rohár (3):
serial: core: Document why UPF_SPD_CUST is not handled in
uart_get_baud_rate()
serial: core: Fix function uart_update_timeout() to handle
UPF_SPD_CUST flag
serial: Fix support for UPF_SPD_* flags in serial drivers
drivers/tty/serial/21285.c | 2 +-
drivers/tty/serial/8250/8250_mtk.c | 2 +-
drivers/tty/serial/8250/8250_omap.c | 2 +-
drivers/tty/serial/8250/8250_port.c | 2 +-
drivers/tty/serial/altera_uart.c | 2 +-
drivers/tty/serial/ar933x_uart.c | 2 +-
drivers/tty/serial/arc_uart.c | 2 +-
drivers/tty/serial/dz.c | 2 +-
drivers/tty/serial/imx.c | 3 +-
drivers/tty/serial/lantiq.c | 2 +-
drivers/tty/serial/lpc32xx_hs.c | 2 +-
drivers/tty/serial/men_z135_uart.c | 2 +-
drivers/tty/serial/mps2-uart.c | 2 +-
drivers/tty/serial/msm_serial.c | 2 +-
drivers/tty/serial/mvebu-uart.c | 2 +-
drivers/tty/serial/owl-uart.c | 2 +-
drivers/tty/serial/pch_uart.c | 2 +-
drivers/tty/serial/pic32_uart.c | 2 +-
drivers/tty/serial/rda-uart.c | 2 +-
drivers/tty/serial/rp2.c | 2 +-
drivers/tty/serial/sccnxp.c | 2 +-
drivers/tty/serial/serial-tegra.c | 2 +-
drivers/tty/serial/serial_core.c | 76 ++++++++++++++++++++++++++++-
drivers/tty/serial/sprd_serial.c | 2 +-
drivers/tty/serial/timbuart.c | 2 +-
drivers/tty/serial/vt8500_serial.c | 2 +-
drivers/tty/serial/xilinx_uartps.c | 2 +-
include/linux/serial_core.h | 2 +
28 files changed, 103 insertions(+), 28 deletions(-)
--
2.20.1
