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

Manfred Huber
2013-03-29T12:52:36Z

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