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serial/ns16550: add an option to avoid hanging on broken platforms

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Some platforms (e.g. IGEPv2 board) has a broken ns16550 UART that
does not set the TEMT bit when the transmitter is empty in SPL.
This makes U-Boot to hang while waiting for TEMT to be set.

Add a new option to avoid this:

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.

Signed-off-by: Javier Martinez Canillas <javier.martinez@collabora.co.uk>
This commit is contained in:
Javier Martinez Canillas 2013-01-07 01:35:20 +00:00 committed by Tom Rini
parent 94bcfe524c
commit 7de0fe1ac3
2 changed files with 10 additions and 0 deletions
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8
README
View file

@ -616,6 +616,14 @@ 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

2
drivers/serial/ns16550.c
View file

@ -36,8 +36,10 @@
void NS16550_init(NS16550_t com_port, int baud_divisor)
{
#if (!defined(CONFIG_SYS_NS16550_BROKEN_TEMT))
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)) || \