On 03/21/2013 05:21:00 PM, Tom Rini wrote:
On Thu, Mar 21, 2013 at 08:03:59PM +0100, Manfred Huber wrote:
> From: Manfred Huber
>
> Beagleboard UART (ns16550) doesn't set the Transmitter Empty (TEMT)
> Bit in SPL.
The serial port behaves differently based on the stage of U-Boot that
is running?
Or is it that the bit doesn't get set until the port has been properly
initialized? Couldn't that happen in a case where SPL isn't used at
all?
> Only Transmitter Hold Register Empty (THRE) Bit is set.
> This makes SPL to hang while waiting for TEMT. Adding the
> CONFIG_SYS_NS16550_BROKEN_TEMT config option and waiting for THRE
> avoid this issue.
>
> Signed-off-by: Manfred Huber <man.hu...@arcor.de>
> ---
> drivers/serial/ns16550.c | 5 ++++-
> include/configs/omap3_beagle.h | 3 +++
> 2 files changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/serial/ns16550.c b/drivers/serial/ns16550.c
> index b2da8b3..6379bcc 100644
> --- a/drivers/serial/ns16550.c
> +++ b/drivers/serial/ns16550.c
> @@ -36,7 +36,10 @@
>
> void NS16550_init(NS16550_t com_port, int baud_divisor)
> {
> -#if (!defined(CONFIG_SYS_NS16550_BROKEN_TEMT))
> +#if defined(CONFIG_SPL_BUILD) &&
defined(CONFIG_SYS_NS16550_BROKEN_TEMT)
> + while (!(serial_in(&com_port->lsr) & UART_LSR_THRE))
> + ;
> +#else
> while (!(serial_in(&com_port->lsr) & UART_LSR_TEMT))
> ;
> #endif
Scott, do you still have access to the failing systems that made us
introduce this change to start with?
It was an intermittent failure seen on a development tree, so not
really. You could try testing it by printing something immediately
before calling NS16550_init(), either in a situation where you know the
serial port is already configured (e.g. by SPL) or by calling
NS16550_init() twice.
Could we perhaps go with the THRE test instead in all cases? Thanks!
Wouldn't that still allow the last character to possibly be corrupted?
-Scott
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