Internal loopback mode can be supported by setting S3C2443_UCON_LOOPBACK bit. The mode & bit can be supported since s3c2410 and later SoCs. We can test it by linux-serial-test program[1] with -k option. It will set TIOCM_LOOP mode during test. -k, --loopback Use internal hardware loop back [1]: https://github.com/cbrake/linux-serial-test Signed-off-by: Chanho Park <chanho61.park@xxxxxxxxxxx> --- drivers/tty/serial/samsung_tty.c | 19 ++++++++++++++++--- 1 file changed, 16 insertions(+), 3 deletions(-) diff --git a/drivers/tty/serial/samsung_tty.c b/drivers/tty/serial/samsung_tty.c index d5ca904def34..d7d035cd95c0 100644 --- a/drivers/tty/serial/samsung_tty.c +++ b/drivers/tty/serial/samsung_tty.c @@ -1002,16 +1002,22 @@ static unsigned int s3c24xx_serial_tx_empty(struct uart_port *port) static unsigned int s3c24xx_serial_get_mctrl(struct uart_port *port) { unsigned int umstat = rd_reg(port, S3C2410_UMSTAT); + unsigned int ucon = rd_reg(port, S3C2410_UCON); + unsigned int mctrl = TIOCM_CAR | TIOCM_DSR; if (umstat & S3C2410_UMSTAT_CTS) - return TIOCM_CAR | TIOCM_DSR | TIOCM_CTS; - else - return TIOCM_CAR | TIOCM_DSR; + mctrl |= TIOCM_CTS; + + if (ucon & S3C2443_UCON_LOOPBACK) + mctrl |= TIOCM_LOOP; + + return mctrl; } static void s3c24xx_serial_set_mctrl(struct uart_port *port, unsigned int mctrl) { unsigned int umcon = rd_regl(port, S3C2410_UMCON); + unsigned int ucon = rd_reg(port, S3C2410_UCON); if (mctrl & TIOCM_RTS) umcon |= S3C2410_UMCOM_RTS_LOW; @@ -1019,6 +1025,13 @@ static void s3c24xx_serial_set_mctrl(struct uart_port *port, unsigned int mctrl) umcon &= ~S3C2410_UMCOM_RTS_LOW; wr_regl(port, S3C2410_UMCON, umcon); + + if (mctrl & TIOCM_LOOP) + ucon |= S3C2443_UCON_LOOPBACK; + else + ucon &= ~S3C2443_UCON_LOOPBACK; + + wr_regl(port, S3C2410_UCON, ucon); } static void s3c24xx_serial_break_ctl(struct uart_port *port, int break_state) -- 2.36.1
