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

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.

---
 README                   |    8 ++++++++
 drivers/serial/ns16550.c |    2 ++
 2 files changed, 10 insertions(+), 0 deletions(-)

index 78f40df..a89861e 100644
@@ -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

index bbd91ca..87a0917 100644
@@ -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)) || \

1.7.7.6

IGEP board PC16550D (ns16550) UART doesn't set the Transmitter Empty (TEMT) Bit in SPL. This makes U-Boot to hang while waiting for TEMT. Add the CONFIG_SYS_NS16550_BROKEN_TEMT config option to avoid this issue.

---
 include/configs/igep00x0.h |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

index 2110e64..a5912f0 100644
@@ -67,6 +67,9 @@
 #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

1.7.7.6

Applied to u-boot-ti/master, thanks!

Tom
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Applied to u-boot-ti/master, thanks!

Tom
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