[PATCH v2] tty: serial: samsung_tty: loopback mode support

[Ilpo Järvinen]

On Tue, 28 Jun 2022, Chanho Park wrote:

> 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 at samsung.com>

Reviewed-by: Ilpo Järvinen <ilpo.jarvinen at linux.intel.com>

You should have included Krzysztof's Reviewed-by when you sent this next 
version so that it won't get lost.

I suspect Greg will again complain that you didn't address his comment 
about the out of the place "-k, --loopback ..." line.


-- 
 i.


> ---
> 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  | \
>