Re: [PATCH v3] tty: serial: samsung_tty: loopback mode support
From: Marek Szyprowski <m.szyprowski@samsung.com>
Date: 2022-07-11 12:33:31
Also in:
linux-samsung-soc, linux-serial
Hi Chanho, On 29.06.2022 02:41, Chanho Park wrote:
quoted hunk ↗ jump to hunk
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 <redacted> Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com> Signed-off-by: Chanho Park <redacted> --- 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);
quoted hunk ↗ jump to hunk
} 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 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel