[U-Boot] [PATCH] ns16550: allow UART address to be set dynamically

[Simon Glass]

Hi Stephen,

On Wed, Dec 12, 2012 at 3:23 PM, Stephen Warren <swarren at wwwdotorg.org> wrote:
> From: Stephen Warren <swarren at nvidia.com>
>
> A single U-Boot binary may support multiple very similar boards. These
> boards may use different UARTs for the main debug console. Hence, it is
> impossible to #define CONFIG_SYS_NS16550_COM1 to some static UART
> address, since the true value may only be determined at run-time, after
> identifying the actual hardware. Provide an API for boards to call to
> set the actual address of the UART, e.g. from spl_board_init() or
> board_early_init_f().
>
> Signed-off-by: Stephen Warren <swarren at nvidia.com>

This seems reasonable in the interim while we are hard-coding things
but needing more flexibility. How do you plan to configure the actual
address - is it with the ODM data or FDT?

One question though - is it not possible to select the correct port
number using environment (say) rather than changing the address of an
existing port? After all, I think we can assume that all available
ports are in the array. Or can we?

Regards,
Simon

> ---
> Note: I have a Tegra patch that will depend on this functionality. I'd
> like to see the patch applied through the Tegra tree if possible, or if
> not, quickly pushed into u-boot/master or u-boot/next so Tom Warren can
> base a Tegra branch on top of it easily without delay.
>
>  drivers/serial/serial_ns16550.c |    5 +++++
>  include/ns16550.h               |    1 +
>  2 files changed, 6 insertions(+)
>
> diff --git a/drivers/serial/serial_ns16550.c b/drivers/serial/serial_ns16550.c
> index fc01a3c..fc8253b 100644
> --- a/drivers/serial/serial_ns16550.c
> +++ b/drivers/serial/serial_ns16550.c
> @@ -166,6 +166,11 @@ static int calc_divisor (NS16550_t port)
>                 (MODE_X_DIV * gd->baudrate);
>  }
>
> +void NS16550_set_dynamic_address(int port, NS16550_t com_port)
> +{
> +       PORT = com_port;
> +}
> +
>  void
>  _serial_putc(const char c,const int port)
>  {
> diff --git a/include/ns16550.h b/include/ns16550.h
> index 51cb5b4..6d7483f 100644
> --- a/include/ns16550.h
> +++ b/include/ns16550.h
> @@ -171,6 +171,7 @@ typedef struct NS16550 *NS16550_t;
>  /* useful defaults for LCR */
>  #define UART_LCR_8N1   0x03
>
> +void NS16550_set_dynamic_address(int port, NS16550_t com_port);
>  void NS16550_init(NS16550_t com_port, int baud_divisor);
>  void NS16550_putc(NS16550_t com_port, char c);
>  char NS16550_getc(NS16550_t com_port);
> --
> 1.7.10.4
>