altera_jtag_uart: bypass when no jtag connection

This patch adds an option to bypass output waiting when there
is no jtag connection. This allows the jtag uart work similar
to a serial uart, ie, boot even without connection.

This option is enabled with CONFIG_ALTERA_JTAG_UART_BYPASS

Signed-off-by: Thomas Chou <thomas@wytron.com.tw>
Signed-off-by: Scott McNutt <smcnutt@psyent.com>

drivers/serial/altera_jtag_uart.c

@@ -38,8 +38,16 @@ int serial_init( void ) { return(0);}
 
 void serial_putc (char c)
 {
-	while (NIOS_JTAG_WSPACE ( readl (&jtag->control)) == 0)
-		WATCHDOG_RESET ();
+	while (1) {
+		unsigned st = readl(&jtag->control);
+		if (NIOS_JTAG_WSPACE(st))
+			break;
+#ifdef CONFIG_ALTERA_JTAG_UART_BYPASS
+		if (!(st & NIOS_JTAG_AC)) /* no connection */
+			return;
+#endif
+		WATCHDOG_RESET();
+	}
 	writel ((unsigned char)c, &jtag->data);
 }