[U-Boot] ns16550: tegra: Specify debugging serial port at boot.

[Stephen Warren <swarren@wwwdotorg.org>]

On 01/06/2012 05:51 AM, Stephen Warren wrote:
> From: Doug Anderson <dianders@chromium.org>
> 
> This works together with a kernel change that looks at the scratchpad
> register to determine which of the many UARTs it should use for early
> printing:
> 
> http://www.spinics.net/lists/arm-kernel/msg154633.html
> 
> While it is unfortunate to need to pass this information in a second way
> (it's already in the device tree), this does allow the very early boot
> code (decompressing stub and early assembly code) to print to the right
> port.
> 
> At the moment, I'm adding this to the UART init function. Alternatively,
> we could add a more complex patch to key off of the 'console' setting.
> 
> Signed-off-by: Doug Anderson <dianders@chromium.org>
> [swarren: Limited the change to Tegra platforms]
> Signed-off-by: Stephen Warren <swarren@nvidia.com>
> Acked-by: Doug Anderson <dianders@chromium.org>

I noticed this patch isn't applied yet that I can find. Are there any
comments on it; can it be applied? Thanks.

For reference, it's in patchwork at:
http://patchwork.ozlabs.org/patch/134712/

> ---
> drivers/serial/ns16550.c |    7 +++++++
>  1 files changed, 7 insertions(+), 0 deletions(-)
> 
> diff --git a/drivers/serial/ns16550.c b/drivers/serial/ns16550.c
> index 0c23955..19a28cd 100644
> --- a/drivers/serial/ns16550.c
> +++ b/drivers/serial/ns16550.c
> @@ -62,6 +62,13 @@ void NS16550_init(NS16550_t com_port, int baud_divisor)
>  	serial_out(0, &com_port->mdr1);
>  #endif
>  #endif /* CONFIG_OMAP */
> +#if defined(CONFIG_TEGRA2)
> +	/*
> +	 * Put a 'D' in the scratchpad to let the kernel know which UART
> +	 * for earlyprintk [D]ebugging.
> +	 */
> +	serial_out('D', &com_port->spr);
> +#endif
>  }
>  
>  #ifndef CONFIG_NS16550_MIN_FUNCTIONS