Re: [PATCH v3 05/10] serial: mps2-uart: add support for early console

Andy Shevchenko
2016-02-16T10:36:09Z

On Tue, Feb 16, 2016 at 12:08 PM, Vladimir Murzin
<vladimir.murzin@arm.com> wrote:
> This adds support early console for MPS2 UART which can be enabled via
> earlycon=mps2,0x40004000

> --- a/drivers/tty/serial/mps2-uart.c
> +++ b/drivers/tty/serial/mps2-uart.c
> @@ -435,6 +435,36 @@ static struct console mps2_uart_console = {
>
> #define MPS2_SERIAL_CONSOLE (&mps2_uart_console)
>
> +static void mps2_early_putchar(struct uart_port *port, int ch)
> +{
> +
> + while (readb(port->membase + UARTn_STATE) & UARTn_STATE_TX_FULL)
> + cpu_relax();

Infinite busy loop?

> +
> + writeb((unsigned char)ch, port->membase + UARTn_DATA);
> +}
> +
> +
> +static void mps2_early_write(struct console *con, const char *s, unsigned n)
> +{
> + struct earlycon_device *dev = con->data;
> +
> + uart_console_write(&dev->port, s, n, mps2_early_putchar);
> +}
> +
> +static int __init mps2_early_console_setup(struct earlycon_device *device,
> + const char *opt)
> +{
> + if (!device->port.membase)
> + return -ENODEV;
> +
> + device->con->write = mps2_early_write;
> +
> + return 0;
> +}
> +EARLYCON_DECLARE(mps2, mps2_early_console_setup);
> +OF_EARLYCON_DECLARE(mps2, "arm,mps2-uart", mps2_early_console_setup);

IIRC Peter Hurley mentioned you don't need to put both anymore, OF_
one is enough.

--
With Best Regards,
Andy Shevchenko