[U-Boot] [PATCH 1/1 v3] omap3_beagle: Enabling UART3 first allows the Transmitter to be empty

Albert ARIBAUD
2013-03-29T09:43:34Z

Hi Manfred,

On Fri, 29 Mar 2013 10:20:25 +0100, Manfred Huber <man.huber@arcor.de>
wrote:

> 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>
> ---

Patch history is missing here.

Also, I would like the commit summary (first commit message line, also
subject of the patch mail) to clearly state what the patch *does* as
opposed to what *happens*, because it is unclear right now if you're
describing the solution or the issue. Something like :

"omap3_beagle: flush UART3 xmit on enable if TEMT is broken"

> README | 8 --------
> drivers/serial/ns16550.c | 16 ++++++++++++++--
> include/configs/igep00x0.h | 3 ---
> 3 files changed, 14 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..2922a2c 100644
> --- a/drivers/serial/ns16550.c
> +++ b/drivers/serial/ns16550.c
> @@ -36,10 +36,22 @@
>
> 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
> _______________________________________________
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Amicalement,
--
Albert.