omap3_beagle: Flush UART3 xmit on enable if TEMT is broken

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>
Tested-by: Javier Martinez Canillas <javier@dowhile0.org>
Tested-by: Andreas Bießmann <andreas.devel@googlemail.com>

README

@@ -627,14 +627,6 @@ 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

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)) || \

include/configs/igep00x0.h

@@ -69,9 +69,6 @@
 #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