On Wed, Jul 13, 2016 at 11:01:35AM +0200, Uwe Kleine-König wrote:
> 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);
That line is a debug left over and obviously should be removed. Other
than taht I still wonder if this patch is good enough for mainline as it
solves a real problem.
Best regards
Uwe
> + return ret;
> }
> #else
> static inline int serial_imx_probe_dt(struct imx_port *sport,
> --
> 2.8.1
>
>
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> linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
--
Pengutronix e.K. | Uwe Kleine-König |
Industrial Linux Solutions | http://www.pengutronix.de/ |
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