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

[Michael Walle]

Hi,

Am 2022-02-17 10:12, schrieb Claudiu.Beznea at microchip.com:
> On 16.02.2022 18:18, 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>
>> ---
>>  drivers/tty/serial/atmel_serial.c | 24 ++++++++++++++++++++++++
>>  1 file changed, 24 insertions(+)
>> 
>> diff --git a/drivers/tty/serial/atmel_serial.c 
>> b/drivers/tty/serial/atmel_serial.c
>> index 2d09a89974a2..50fc6d51ff0d 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(atmelserial, "atmel,at91rm9200-usart",
>> +                   atmel_early_console_setup);
>> +OF_EARLYCON_DECLARE(atmelserial, "atmel,at91sam9260-usart",
> 
> 
> For consistency with the rest of the naming in this file could you name 
> it
> atmel_serial?

Sure, I don't have an opinion on that. It's done both ways:
omap-serial.c:OF_EARLYCON_DECLARE(omapserial, "ti,omap2-uart", 
early_omap_serial_setup);
bcm63xx_uart.c:OF_EARLYCON_DECLARE(bcm63xx_uart, "brcm,bcm6345-uart", 
bcm_early_console_setup);
...

> Also, it would be good to select SERIAL_EARLYCON in Kconfig to have it
> available also for production w/o changing defconfigs.

Ahh, missed that these are enabled for all the other Kconfig symbols.
Will add it to SERIAL_ATMEL_CONSOLE.

-michael