serial/serial_arc: Implement debug serial

Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>

drivers/serial/Kconfig

@@ -197,6 +197,15 @@ config DEBUG_UART_AR933X
 	  driver will be available until the real driver model serial is
 	  running.
 
+config DEBUG_ARC_SERIAL
+	bool "ARC UART"
+	depends on ARC_SERIAL
+	help
+	  Select this to enable a debug UART using the ARC UART driver.
+	  You will need to provide parameters to make this work. The
+	  driver will be available until the real driver model serial is
+	  running.
+
 config DEBUG_UART_ATMEL
 	bool "Atmel USART"
 	help

drivers/serial/serial_arc.c

@@ -130,3 +130,29 @@ U_BOOT_DRIVER(serial_arc) = {
 	.ops	= &arc_serial_ops,
 	.flags = DM_FLAG_PRE_RELOC,
 };
+
+#ifdef CONFIG_DEBUG_ARC_SERIAL
+#include <debug_uart.h>
+
+static inline void _debug_uart_init(void)
+{
+	struct arc_serial_regs *regs = (struct arc_serial_regs *)CONFIG_DEBUG_UART_BASE;
+	int arc_console_baud = CONFIG_DEBUG_UART_CLOCK / (CONFIG_BAUDRATE * 4) - 1;
+
+	writeb(arc_console_baud & 0xff, &regs->baudl);
+	writeb((arc_console_baud & 0xff00) >> 8, &regs->baudh);
+}
+
+static inline void _debug_uart_putc(int c)
+{
+	struct arc_serial_regs *regs = (struct arc_serial_regs *)CONFIG_DEBUG_UART_BASE;
+
+	while (!(readb(&regs->status) & UART_TXEMPTY))
+		;
+
+	writeb(c, &regs->data);
+}
+
+DEBUG_UART_FUNCS
+
+#endif