diff options
| author | Stefan Agner <stefan@agner.ch> | 2018-04-19 17:39:16 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2018-04-23 09:53:36 +0200 |
| commit | 6d215f83e5fccb3dd023e97fef1bd0029bfedde9 (patch) | |
| tree | 601f424331f62f7ebad83ac850477845a055e781 /drivers/tty | |
| parent | 46c6975a1fd9794ed979565235d24b2f5004e014 (diff) | |
| download | linux-6d215f83e5fccb3dd023e97fef1bd0029bfedde9.tar.bz2 | |
serial: imx: warn user when using unsupported configuration
When using half-duplex mode (which disables receiver during txing)
the RTS signal cannot be driven low during transmission when using
i.MX UART RTS/CTS control. This seems to be a limitation of the
i.MX UART IP: The RTS (CTS_B) signal is controlled by the receiver.
When the receiver is disabled, the signal stays in UART logic idle
state which is high...
If SER_RS485_RTS_ON_SEND is used, RTS needs to be high active during
transmission. Since this is the default state of the RTS (CTS_B)
signal when the receiver is off, half-duplex mode in this
configuration works fine.
However, a low-active RTS signal (flag SER_RS485_RTS_ON_SEND not set)
cannot be generated when the receiver is turned off.
Print an error if the user selects this unsupported configuration
(both SER_RS485_RTS_ON_SEND and SER_RS485_RX_DURING_TX unset) and
configure the closest working configuration (set the
SER_RS485_RX_DURING_TX flag).
Signed-off-by: Stefan Agner <stefan@agner.ch>
Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/tty')
| -rw-r--r-- | drivers/tty/serial/imx.c | 17 |
1 files changed, 17 insertions, 0 deletions
diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c index 91f3a1a5cb7f..65d7a2bfb6d2 100644 --- a/drivers/tty/serial/imx.c +++ b/drivers/tty/serial/imx.c @@ -1833,6 +1833,11 @@ static int imx_uart_rs485_config(struct uart_port *port, rs485conf->flags &= ~SER_RS485_ENABLED; if (rs485conf->flags & SER_RS485_ENABLED) { + /* Enable receiver if low-active RTS signal is requested */ + if (sport->have_rtscts && !sport->have_rtsgpio && + !(rs485conf->flags & SER_RS485_RTS_ON_SEND)) + rs485conf->flags |= SER_RS485_RX_DURING_TX; + /* disable transmitter */ ucr2 = imx_uart_readl(sport, UCR2); if (rs485conf->flags & SER_RS485_RTS_AFTER_SEND) @@ -2265,6 +2270,18 @@ static int imx_uart_probe(struct platform_device *pdev) (!sport->have_rtscts && !sport->have_rtsgpio)) dev_err(&pdev->dev, "no RTS control, disabling rs485\n"); + /* + * If using the i.MX UART RTS/CTS control then the RTS (CTS_B) + * signal cannot be set low during transmission in case the + * receiver is off (limitation of the i.MX UART IP). + */ + if (sport->port.rs485.flags & SER_RS485_ENABLED && + sport->have_rtscts && !sport->have_rtsgpio && + (!(sport->port.rs485.flags & SER_RS485_RTS_ON_SEND) && + !(sport->port.rs485.flags & SER_RS485_RX_DURING_TX))) + dev_err(&pdev->dev, + "low-active RTS not possible when receiver is off, enabling receiver\n"); + imx_uart_rs485_config(&sport->port, &sport->port.rs485); /* Disable interrupts before requesting them */ |