[U-Boot] [PATCH] serial: Enable checking UART is ready for console based on device tree

[Tien Fong Chee]

This patch would do checking on device tree to ensure the UART exist
in the system and ready for console before setting have_console to true.
This is required to avoid unexpected behavior such as hang during UART
initialization.

Signed-off-by: Tien Fong Chee <tfchee at altera.com>
Cc: Dinh Nguyen <dinguyen at opensource.altera.com>
Cc: Dinh Nguyen <dinh.linux at gmail.com>
Cc: ChinLiang <clsee at altera.com>
Cc: Thomas Chou <thomas at wytron.com.tw>
Cc: Simon Glass <sjg at chromium.org>
Cc: Marek Vasut <marex at denx.de>
---
 common/console.c                  |   11 ++++---
 common/spl/spl.c                  |    3 +-
 drivers/serial/serial.c           |   58 +++++++++++++++++++++++++++++++++++-
 include/asm-generic/global_data.h |    1 +
 include/serial.h                  |    1 +
 5 files changed, 66 insertions(+), 8 deletions(-)

diff --git a/common/console.c b/common/console.c
index 12293f3..c37486c 100644
--- a/common/console.c
+++ b/common/console.c
@@ -690,14 +690,15 @@ int console_assign(int file, const char *devname)
 /* Called before relocation - use serial functions */
 int console_init_f(void)
 {
-	gd->have_console = 1;
-
+	if(gd->uart_ready_for_console) {
+		gd->have_console = 1;
 #ifdef CONFIG_SILENT_CONSOLE
-	if (getenv("silent") != NULL)
-		gd->flags |= GD_FLG_SILENT;
+		if (getenv("silent") != NULL)
+			gd->flags |= GD_FLG_SILENT;
 #endif
 
-	print_pre_console_buffer(PRE_CONSOLE_FLUSHPOINT1_SERIAL);
+		print_pre_console_buffer(PRE_CONSOLE_FLUSHPOINT1_SERIAL);
+	}
 
 	return 0;
 }
diff --git a/common/spl/spl.c b/common/spl/spl.c
index b7ec333..c18827d 100644
--- a/common/spl/spl.c
+++ b/common/spl/spl.c
@@ -488,7 +488,8 @@ void preloader_console_init(void)
 
 	serial_init();		/* serial communications setup */
 
-	gd->have_console = 1;
+	if(gd->uart_ready_for_console)
+		gd->have_console = 1;
 
 	puts("\nU-Boot SPL " PLAIN_VERSION " (" U_BOOT_DATE " - " \
 			U_BOOT_TIME ")\n");
diff --git a/drivers/serial/serial.c b/drivers/serial/serial.c
index f1bd15b..95690e0 100644
--- a/drivers/serial/serial.c
+++ b/drivers/serial/serial.c
@@ -35,6 +35,51 @@ static void serial_null(void)
 }
 
 /**
+ * uart_console_null() - This empty function would be used if UART console checking
+ *                       function is not compiled into U-boot.
+ *
+ * This routine returns true to indicate UART is ready for console by default.
+ * The driver is aliased to this empty function in case
+ * the driver is not compiled into U-Boot.
+ */
+static int uart_console_null(void)
+{
+	return 1;
+}
+
+/**
+ * uart_console_func() - Forward declare of driver checking UART is ready based
+ * 			 on device tree.
+ * @name:	Name of driver which checking UART is ready based on device tree .
+ *
+ * This macro expands onto forward declaration of a driver checking
+ * UART is ready based on device tree, which allows own assigned function name.
+ * The declaration is made weak and aliases to uart_console_null() so in case
+ * the driver is not compiled in, the function is still declared and can
+ * be used, but aliases to uart_console_null() and thus is optimized away.
+ */
+#define uart_console_func(name)					\
+	int name(const void *blob)						\
+		__attribute__((weak, alias("uart_console_null")));
+
+uart_console_func(is_default_uart_console_true);
+
+/**
+ * is_uart_console_true() - Common function to abstract the specific UART
+ *			    console checking function.
+ *
+ * This is common interface for specific UART console checking function.
+ */
+int is_uart_console_true(const void *blob)
+{
+	int ret = 0;
+
+	ret |= is_default_uart_console_true(blob);
+
+	return ret;
+}
+
+/**
  * on_baudrate() - Update the actual baudrate when the env var changes
  *
  * This will check for a valid baudrate and only apply it if valid.
@@ -415,8 +460,17 @@ static struct serial_device *get_current(void)
  */
 int serial_init(void)
 {
-	gd->flags |= GD_FLG_SERIAL_READY;
-	return get_current()->start();
+	if(is_uart_console_true(gd->fdt_blob))
+		gd->uart_ready_for_console = 1;
+	else
+		gd->uart_ready_for_console = 0;
+
+	if(gd->uart_ready_for_console) {
+		gd->flags |= GD_FLG_SERIAL_READY;
+		return get_current()->start();
+	}
+
+	return 0;
 }
 
 /**
diff --git a/include/asm-generic/global_data.h b/include/asm-generic/global_data.h
index a6d1d2a..1cb7ef7 100644
--- a/include/asm-generic/global_data.h
+++ b/include/asm-generic/global_data.h
@@ -44,6 +44,7 @@ typedef struct global_data {
 #ifdef CONFIG_BOARD_TYPES
 	unsigned long board_type;
 #endif
+	unsigned long uart_ready_for_console; /* UART ready to support console */
 	unsigned long have_console;	/* serial_init() was called */
 #ifdef CONFIG_PRE_CONSOLE_BUFFER
 	unsigned long precon_buf_idx;	/* Pre-Console buffer index */
diff --git a/include/serial.h b/include/serial.h
index 47332c5..a95bf70 100644
--- a/include/serial.h
+++ b/include/serial.h
@@ -50,6 +50,7 @@ extern void serial_initialize(void);
 extern void serial_stdio_init(void);
 extern int serial_assign(const char *name);
 extern void serial_reinit_all(void);
+extern int is_uart_console_true(const void *blob);
 
 /* For usbtty */
 #ifdef CONFIG_USB_TTY
-- 
1.7.7.4