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.huber@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