earlycon issues in -next with amba-pl011 updates

[Jun Nie]

2015-08-11 7:23 GMT+08:00 Leif Lindholm <leif.lindholm at linaro.org>:
> Hi all,
>
> The kernelci.org bot picked up a complete boot failure (no output past
> UEFI stub) with next-20150806 and Tyler bisected it down to somewhere
> in
> 8cd90e5 uart: pl011: Add support to ZTE ZX296702 uart
> 09dcc7d uart: pl011: Improve LCRH register access decision
> 2c096a9 uart: pl011: Introduce register look up table
> 7b753f3 uart: pl011: Introduce register accessor
>
> The issue only appears with earlycon on command line, for pl011
> consoles.
>
> Some investigation shows that the cause lies with
> commit 7b753f318d14 ("uart: pl011: Introduce register accessor")
> and
> commit 2c096a9eedc6 ("uart: pl011: Introduce register look up table")
>
> Specifically, the changes to pl011_putc() are incorrect:
> The new pl011_ accessors take a (struct uart_amba_port *) input, but
> pl011_putc() directly uses the incoming (struct uart_port *) for this.
>
> Apart from ending up with an unintended/incorrect UART base address,
> the introduction of the lookup table for register offsets also means
> the accessors try to dereference (struct uart_amba_port *)->reg_lut.
>
> The below is a hack that shows/resolves the issue, but some
> refactoring of the original patches might be in order.
>
> /
>     Leif

Leif,

Sorry for the inconvenience. I do not have idea of early console till
now and I always have debug console for early panic debug. Learned
more from this issue.

Suppose Peter's patch will resolve your issue.

Jun

>
> diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c
> index 2af09ab..452dbba 100644
> --- a/drivers/tty/serial/amba-pl011.c
> +++ b/drivers/tty/serial/amba-pl011.c
> @@ -2348,13 +2348,14 @@ static struct console amba_console = {
>
>  static void pl011_putc(struct uart_port *port, int c)
>  {
> -       struct uart_amba_port *uap =
> -           container_of(port, struct uart_amba_port, port);
> +       struct uart_amba_port uap;
> +       uap.port = *port;
> +       uap.reg_lut = arm_reg;
>
> -       while (pl011_readw(uap, REG_FR) & UART01x_FR_TXFF)
> +       while (pl011_readw(&uap, REG_FR) & UART01x_FR_TXFF)
>                 ;
> -       pl011_writeb(uap, c, REG_DR);
> -       while (pl011_readw(uap, REG_FR) & uap->fr_busy)
> +       pl011_writeb(&uap, c, REG_DR);
> +       while (pl011_readw(&uap, REG_FR) & UART01x_FR_BUSY)
>                 ;
>  }
>
> --
> 2.1.4
>
>
>