[U-Boot] [PATCH 1/1 v5] omap3_beagle: Flush UART3 xmit on enable if TEMT is broken

[Javier Martinez Canillas <javier@dowhile0.org>]

On Fri, Mar 29, 2013 at 1:52 PM, Manfred Huber <man.huber@arcor.de> wrote:
> From: Manfred Huber <man.huber@arcor.de>
>
> Flush UART3 xmit on enable if TEMT is broken
>
> On some OMAP3 devices when UART3 is configured for boot mode before SPL starts
> only THRE bit is set. We have to empty the transmitter before initialization
> starts. This patch avoids the use of CONFIG_SYS_NS16550_BROKEN_TEMT.
>
> Signed-off-by: Manfred Huber <man.huber@arcor.de>
> ---
> Changes since v4:
>         - Changed multiline comment.
>
> Changes since v3:
>         - Changed commit summary and added version history.
>
> Changes since v2:
>         - Removing CONFIG_SYS_NS16550_BROKEN_TEMT in README and igep00x0.h.
>
> Changes since v1:
>         - Replaced CONFIG_SYS_NS16550_BROKEN_TEMT with initial configuration of
>           UART.
>
>  README                     |    8 --------
>  drivers/serial/ns16550.c   |   18 ++++++++++++++++--
>  include/configs/igep00x0.h |    3 ---
>  3 files changed, 16 insertions(+), 13 deletions(-)
>
> diff --git a/README b/README
> index a336476..e6b3a50 100644
> --- a/README
> +++ b/README
> @@ -616,14 +616,6 @@ The following options need to be configured:
>                 boot loader that has already initialized the UART.  Define this
>                 variable to flush the UART at init time.
>
> -               CONFIG_SYS_NS16550_BROKEN_TEMT
> -
> -               16550 UART set the Transmitter Empty (TEMT) Bit when all output
> -               has finished and the transmitter is totally empty. U-Boot waits
> -               for this bit to be set to initialize the serial console. On some
> -               broken platforms this bit is not set in SPL making U-Boot to
> -               hang while waiting for TEMT. Define this option to avoid it.
> -
>
>  - Console Interface:
>                 Depending on board, define exactly one serial port
> diff --git a/drivers/serial/ns16550.c b/drivers/serial/ns16550.c
> index 87a0917..a9352fb 100644
> --- a/drivers/serial/ns16550.c
> +++ b/drivers/serial/ns16550.c
> @@ -36,10 +36,24 @@
>
>  void NS16550_init(NS16550_t com_port, int baud_divisor)
>  {
> -#if (!defined(CONFIG_SYS_NS16550_BROKEN_TEMT))
> +#if (defined(CONFIG_SPL_BUILD) && defined(CONFIG_OMAP34XX))
> +       /*
> +        * On some OMAP3 devices when UART3 is configured for boot mode before
> +        * SPL starts only THRE bit is set. We have to empty the transmitter
> +        * before initialization starts.
> +        */
> +       if ((serial_in(&com_port->lsr) & (UART_LSR_TEMT | UART_LSR_THRE))
> +            == UART_LSR_THRE) {
> +               serial_out(UART_LCR_DLAB, &com_port->lcr);
> +               serial_out(baud_divisor & 0xff, &com_port->dll);
> +               serial_out((baud_divisor >> 8) & 0xff, &com_port->dlm);
> +               serial_out(UART_LCRVAL, &com_port->lcr);
> +               serial_out(0, &com_port->mdr1);
> +       }
> +#endif
> +
>         while (!(serial_in(&com_port->lsr) & UART_LSR_TEMT))
>                 ;
> -#endif
>
>         serial_out(CONFIG_SYS_NS16550_IER, &com_port->ier);
>  #if (defined(CONFIG_OMAP) && !defined(CONFIG_OMAP3_ZOOM2)) || \
> diff --git a/include/configs/igep00x0.h b/include/configs/igep00x0.h
> index f8131b1..0617a58 100644
> --- a/include/configs/igep00x0.h
> +++ b/include/configs/igep00x0.h
> @@ -67,9 +67,6 @@
>  #define CONFIG_SYS_NS16550_REG_SIZE    (-4)
>  #define CONFIG_SYS_NS16550_CLK         V_NS16550_CLK
>
> -/* define to avoid U-Boot to hang while waiting for TEMT */
> -#define CONFIG_SYS_NS16550_BROKEN_TEMT
> -
>  /* select serial console configuration */
>  #define CONFIG_CONS_INDEX              3
>  #define CONFIG_SYS_NS16550_COM3                OMAP34XX_UART3

Hi Manfred,

I tested your patch on my IGEPv2 and is booting correctly, so:

Tested-by: Javier Martinez Canillas <javier@dowhile0.org>

Thanks a lot for working on this!

Best regards,
Javier