[U-Boot] [RFC PATCH] serial: omap: Support debug UART

[Lokesh Vutla]

Add debug UART functions to permit omap specific ns16550 to
provide an early debug UART. This is mostly in common with
DEBUG_UART_NS16550 except for Mode definition register which
is required for selecting UART mode(16x auto-baud or 13x mode).

Signed-off-by: Lokesh Vutla <lokeshvutla at ti.com>
---
- I understand it is duplication of code, but I guess the idea
  is not to use NS16550_init() as it has lot of ifdefs. Please
  advice if this can be improved.

 drivers/serial/Kconfig   |  7 +++++++
 drivers/serial/ns16550.c | 47 ++++++++++++++++++++++++++++++++++++-----------
 include/debug_uart.h     | 11 +++++++++++
 3 files changed, 54 insertions(+), 11 deletions(-)

diff --git a/drivers/serial/Kconfig b/drivers/serial/Kconfig
index c0ec2ec2e4..5db9ec744e 100644
--- a/drivers/serial/Kconfig
+++ b/drivers/serial/Kconfig
@@ -238,6 +238,13 @@ config DEBUG_UART_UNIPHIER
 	  driver will be available until the real driver-model serial is
 	  running.
 
+config DEBUG_UART_OMAP
+	bool "OMAP uart"
+	help
+	  Select this to enable a debug UART using the omap ns16550 driver.
+	  You will need to provide parameters to make this work. The driver
+	  will be available until the real driver model serial is running.
+
 endchoice
 
 config DEBUG_UART_BASE
diff --git a/drivers/serial/ns16550.c b/drivers/serial/ns16550.c
index 4f86780cb1..ca55df78b7 100644
--- a/drivers/serial/ns16550.c
+++ b/drivers/serial/ns16550.c
@@ -246,17 +246,6 @@ int NS16550_tstc(NS16550_t com_port)
 
 #include <debug_uart.h>
 
-#define serial_dout(reg, value)	\
-	serial_out_shift((char *)com_port + \
-		((char *)reg - (char *)com_port) * \
-			(1 << CONFIG_DEBUG_UART_SHIFT), \
-		CONFIG_DEBUG_UART_SHIFT, value)
-#define serial_din(reg) \
-	serial_in_shift((char *)com_port + \
-		((char *)reg - (char *)com_port) * \
-			(1 << CONFIG_DEBUG_UART_SHIFT), \
-		CONFIG_DEBUG_UART_SHIFT)
-
 static inline void _debug_uart_init(void)
 {
 	struct NS16550 *com_port = (struct NS16550 *)CONFIG_DEBUG_UART_BASE;
@@ -293,6 +282,42 @@ DEBUG_UART_FUNCS
 
 #endif
 
+#ifdef CONFIG_DEBUG_UART_OMAP
+
+#include <debug_uart.h>
+
+static inline void _debug_uart_init(void)
+{
+	struct NS16550 *com_port = (struct NS16550 *)CONFIG_DEBUG_UART_BASE;
+	int baud_divisor;
+
+	baud_divisor = ns16550_calc_divisor(com_port, CONFIG_DEBUG_UART_CLOCK,
+					    CONFIG_BAUDRATE);
+	serial_dout(&com_port->ier, CONFIG_SYS_NS16550_IER);
+	serial_dout(&com_port->mdr1, 0x7);
+	serial_dout(&com_port->mcr, UART_MCRVAL);
+	serial_dout(&com_port->fcr, UART_FCR_DEFVAL);
+
+	serial_dout(&com_port->lcr, UART_LCR_BKSE | UART_LCRVAL);
+	serial_dout(&com_port->dll, baud_divisor & 0xff);
+	serial_dout(&com_port->dlm, (baud_divisor >> 8) & 0xff);
+	serial_dout(&com_port->lcr, UART_LCRVAL);
+	serial_dout(&com_port->mdr1, 0x0);
+}
+
+static inline void _debug_uart_putc(int ch)
+{
+	struct NS16550 *com_port = (struct NS16550 *)CONFIG_DEBUG_UART_BASE;
+
+	while (!(serial_din(&com_port->lsr) & UART_LSR_THRE))
+		;
+	serial_dout(&com_port->thr, ch);
+}
+
+DEBUG_UART_FUNCS
+
+#endif
+
 #ifdef CONFIG_DM_SERIAL
 static int ns16550_serial_putc(struct udevice *dev, const char ch)
 {
diff --git a/include/debug_uart.h b/include/debug_uart.h
index 2980ae6200..6f0b0c5e15 100644
--- a/include/debug_uart.h
+++ b/include/debug_uart.h
@@ -111,6 +111,17 @@ void printhex8(uint value);
 #define _DEBUG_UART_ANNOUNCE
 #endif
 
+#define serial_dout(reg, value)	\
+	serial_out_shift((char *)com_port + \
+		((char *)reg - (char *)com_port) * \
+			(1 << CONFIG_DEBUG_UART_SHIFT), \
+		CONFIG_DEBUG_UART_SHIFT, value)
+#define serial_din(reg) \
+	serial_in_shift((char *)com_port + \
+		((char *)reg - (char *)com_port) * \
+			(1 << CONFIG_DEBUG_UART_SHIFT), \
+		CONFIG_DEBUG_UART_SHIFT)
+
 /*
  * Now define some functions - this should be inserted into the serial driver
  */
-- 
2.11.0