A part of my machine looks as follows (simplified): ,------------------------. | ,---------. | | | imx25 o--RX----◁---o--- | | o--GPIO--' | | `---------' | `------------------------' that is, there is a driver on the RX line that must be enabled before the UART can be used. (That is necessary because the default mux of the RX pad after reset is an output.) To represent this in the device tree I do: pinctrl_uart5: uart5 { fsl,pins = < ... MX25_PAD_LBA__UART5_RXD 0x00000000 MX25_PAD_CS5__GPIO_3_21 0x00002001 ... }; &uart5 { pinctrl-names = "default"; pinctrl-0 = <&pinctrl_uart5>; enable-gpio = <&gpio3 21 GPIO_ACTIVE_LOW>; ... }; This way it's ensured that the gpio is only enabled when the LBA pad is muxed as RX (together with the bootloader that sets the GPIO high). Signed-off-by: Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxxxx> --- Hello, I'm not sure about the naming. Do you have a better suggestion how to handle this situation? Best regards Uwe drivers/tty/serial/imx.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c index 0df2b1c091ae..56eaa18aa5be 100644 --- a/drivers/tty/serial/imx.c +++ b/drivers/tty/serial/imx.c @@ -39,6 +39,7 @@ #include <linux/of_device.h> #include <linux/io.h> #include <linux/dma-mapping.h> +#include <linux/gpio/consumer.h> #include <asm/irq.h> #include <linux/platform_data/serial-imx.h> @@ -1987,7 +1988,9 @@ static int serial_imx_probe_dt(struct imx_port *sport, if (of_get_property(np, "fsl,dte-mode", NULL)) sport->dte_mode = 1; - return 0; + ret = PTR_ERR_OR_ZERO(devm_gpiod_get_optional(&pdev->dev, "enable", GPIOD_OUT_HIGH)); + dev_info(&pdev->dev, "Tralala: ret = %d\n", ret); + return ret; } #else static inline int serial_imx_probe_dt(struct imx_port *sport, -- 2.8.1 -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html