[PATCH v2] tty: serial: atmel: add earlycon support

[Claudiu.Beznea at microchip.com]

On 17.02.2022 11:46, Michael Walle wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> 
> Add early console support which relies on the bootloader for the
> initialization of the UART.
> Please note, that the compatibles are taken from at91-usart MFD
> driver.
> 
> Signed-off-by: Michael Walle <michael at walle.cc>

On SAMA7G5:
Tested-by: Claudiu Beznea <claudiu.beznea at microchip.com>
Reviewed-by: Claudiu Beznea <claudiu.beznea at microchip.com>

> ---
>  drivers/tty/serial/Kconfig        |  1 +
>  drivers/tty/serial/atmel_serial.c | 24 ++++++++++++++++++++++++
>  2 files changed, 25 insertions(+)
> 
> diff --git a/drivers/tty/serial/Kconfig b/drivers/tty/serial/Kconfig
> index 0e5ccb25bdb1..407a98ec0791 100644
> --- a/drivers/tty/serial/Kconfig
> +++ b/drivers/tty/serial/Kconfig
> @@ -139,6 +139,7 @@ config SERIAL_ATMEL_CONSOLE
>         bool "Support for console on AT91 serial port"
>         depends on SERIAL_ATMEL=y
>         select SERIAL_CORE_CONSOLE
> +       select SERIAL_EARLYCON
>         help
>           Say Y here if you wish to use an on-chip UART on a Atmel
>           AT91 processor as the system console (the system
> diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c
> index 2d09a89974a2..73d43919898d 100644
> --- a/drivers/tty/serial/atmel_serial.c
> +++ b/drivers/tty/serial/atmel_serial.c
> @@ -2673,6 +2673,30 @@ static struct console atmel_console = {
>         .data           = &atmel_uart,
>  };
> 
> +static void atmel_serial_early_write(struct console *con, const char *s,
> +                                    unsigned int n)
> +{
> +       struct earlycon_device *dev = con->data;
> +
> +       uart_console_write(&dev->port, s, n, atmel_console_putchar);
> +}
> +
> +static int __init atmel_early_console_setup(struct earlycon_device *device,
> +                                           const char *options)
> +{
> +       if (!device->port.membase)
> +               return -ENODEV;
> +
> +       device->con->write = atmel_serial_early_write;
> +
> +       return 0;
> +}
> +
> +OF_EARLYCON_DECLARE(atmel_serial, "atmel,at91rm9200-usart",
> +                   atmel_early_console_setup);
> +OF_EARLYCON_DECLARE(atmel_serial, "atmel,at91sam9260-usart",
> +                   atmel_early_console_setup);
> +
>  #define ATMEL_CONSOLE_DEVICE   (&atmel_console)
> 
>  #else
> --
> 2.30.2
>