Internal loopback mode can be supported by setting
UCON register's Loopback Mode bit. The mode & bit can be supported since
s3c2410 and later SoCs. The prefix of LOOPBACK / BIT(5) naming should be
also changed to S3C2410_ to avoid confusion.
We can test it by linux-serial-test program
with -k option. The tool will set TIOCM_LOOP mode when the option is
specified.
-k, --loopback Use internal hardware loop back
Signed-off-by: Chanho Park <chanho61.park@xxxxxxxxxxx>
---
Changes from v1:
- Drop TIOCM_LOOP return from s3c24xx_serial_get_mctrl as pointed out by
Ilpo. Documentation/driver-api/serial/driver.rst indicates the bit is
only for set_mctrl.
- Change the loopback bit definition from S3C2443_UCON_LOOPBACK to
S3C2410_UCON_LOOPBACK because it has been supported since s3c2410.
- Remove the unnecessary footnote and put a blank line before Signed-off-by
drivers/tty/serial/samsung_tty.c | 8 ++++++++
include/linux/serial_s3c.h | 2 +-
2 files changed, 9 insertions(+), 1 deletion(-)
diff --git a/drivers/tty/serial/samsung_tty.c b/drivers/tty/serial/samsung_tty.c
index d5ca904def34..03ef4ff506fd 100644
--- a/drivers/tty/serial/samsung_tty.c
+++ b/drivers/tty/serial/samsung_tty.c
@@ -1012,6 +1012,7 @@ static unsigned int s3c24xx_serial_get_mctrl(struct uart_port *port)
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 +1020,13 @@ 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 |= S3C2410_UCON_LOOPBACK;
+ else
+ ucon &= ~S3C2410_UCON_LOOPBACK;
+
+ wr_regl(port, S3C2410_UCON, ucon);
}
static void s3c24xx_serial_break_ctl(struct uart_port *port, int break_state)
diff --git a/include/linux/serial_s3c.h b/include/linux/serial_s3c.h
index dec15f5b3dec..1672cf0810ef 100644
--- a/include/linux/serial_s3c.h
+++ b/include/linux/serial_s3c.h
@@ -83,7 +83,7 @@
#define S3C2410_UCON_RXIRQMODE (1<<0)
#define S3C2410_UCON_RXFIFO_TOI (1<<7)
#define S3C2443_UCON_RXERR_IRQEN (1<<6)
-#define S3C2443_UCON_LOOPBACK (1<<5)
+#define S3C2410_UCON_LOOPBACK (1<<5)
#define S3C2410_UCON_DEFAULT (S3C2410_UCON_TXILEVEL | \
S3C2410_UCON_RXILEVEL | \
--
2.36.1
