Hi Chanho,
On 29.06.2022 02:41, 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_ in order to avoid confusion.
>
> Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxx>
> Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxxx>
> Signed-off-by: Chanho Park <chanho61.park@xxxxxxxxxxx>
> ---
> Changes from v2:
> - Add Ilop and Krzysztof's R-B tags
> - Drop linux-serial-test related commit messages
> - Wrap commit messages at 72 columns
>
> 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);
S3C2410_UCON must be modified at least under the local_irq_save() or port lock, otherwise it breaks kernel console operation on older Exynos SoCs (especially when DMA mode is used).
The above read-modify-write sequence should be replaced with the following pattern:
if (mctrl & TIOCM_LOOP)
s3c24xx_set_bit(port, S3C2410_UCON_LOOPBACK, S3C2410_UCON);
else
s3c24xx_clear_bit(port, S3C2410_UCON_LOOPBACK, S3C2410_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 | \
Best regards
--
Marek Szyprowski, PhD
Samsung R&D Institute Poland
