console: Implement flush() function

On certain places it is required to flush output print buffers to ensure
that text strings were sent to console or serial devices. For example when
printing message that U-Boot is going to boot kernel or when U-Boot is
going to change baudrate of terminal device.

Therefore introduce a new flush() and fflush() functions into console code.
These functions will call .flush callback of associated stdio_dev device.

As this function may increase U-Boot side, allow to compile U-Boot without
this function. For this purpose there is a new config CONSOLE_FLUSH_SUPPORT
which is enabled by default and can be disabled. It is a good idea to have
this option enabled for all boards which have enough space for it.

When option is disabled when U-Boot defines just empty static inline
function fflush() to avoid ifdefs in other code.

Signed-off-by: Pali Rohár <pali@kernel.org>
Reviewed-by: Simon Glass <sjg@chromium.org>

2 files changed, 67 insertions, 0 deletions

diff --git a/common/Kconfig b/common/Kconfig
index b776c5ca1e..6591acd2fd 100644
--- a/common/Kconfig
+++ b/common/Kconfig
@@ -186,6 +186,12 @@ config PRE_CON_BUF_ADDR
 	  We should consider removing this option and allocating the memory
 	  in board_init_f_init_reserve() instead.
 
+config CONSOLE_FLUSH_SUPPORT
+	bool "Enable console flush support"
+	default y
+	help
+	  This enables compilation of flush() function for console flush support.
+
 config CONSOLE_MUX
 	bool "Enable console multiplexing"
 	default y if DM_VIDEO || VIDEO || LCD
diff --git a/common/console.c b/common/console.c
index e5be6ff44b..ce0c9b69f5 100644
--- a/common/console.c
+++ b/common/console.c
@@ -199,6 +199,7 @@ static int console_setfile(int file, struct stdio_dev * dev)
 		case stdout:
 			gd->jt->putc  = putc;
 			gd->jt->puts  = puts;
+			STDIO_DEV_ASSIGN_FLUSH(gd->jt, flush);
 			gd->jt->printf = printf;
 			break;
 		}
@@ -364,6 +365,19 @@ static void console_puts(int file, const char *s)
 	}
 }
 
+#ifdef CONFIG_CONSOLE_FLUSH_SUPPORT
+static void console_flush(int file)
+{
+	int i;
+	struct stdio_dev *dev;
+
+	for_each_console_dev(i, file, dev) {
+		if (dev->flush != NULL)
+			dev->flush(dev);
+	}
+}
+#endif
+
 #if CONFIG_IS_ENABLED(SYS_CONSOLE_IS_IN_ENV)
 static inline void console_doenv(int file, struct stdio_dev *dev)
 {
@@ -413,6 +427,14 @@ static inline void console_puts(int file, const char *s)
 	stdio_devices[file]->puts(stdio_devices[file], s);
 }
 
+#ifdef CONFIG_CONSOLE_FLUSH_SUPPORT
+static inline void console_flush(int file)
+{
+	if (stdio_devices[file]->flush)
+		stdio_devices[file]->flush(stdio_devices[file]);
+}
+#endif
+
 #if CONFIG_IS_ENABLED(SYS_CONSOLE_IS_IN_ENV)
 static inline void console_doenv(int file, struct stdio_dev *dev)
 {
@@ -526,6 +548,14 @@ void fputs(int file, const char *s)
 		console_puts(file, s);
 }
 
+#ifdef CONFIG_CONSOLE_FLUSH_SUPPORT
+void fflush(int file)
+{
+	if (file < MAX_FILES)
+		console_flush(file);
+}
+#endif
+
 int fprintf(int file, const char *fmt, ...)
 {
 	va_list args;
@@ -740,6 +770,37 @@ void puts(const char *s)
 	}
 }
 
+#ifdef CONFIG_CONSOLE_FLUSH_SUPPORT
+void flush(void)
+{
+	if (!gd)
+		return;
+
+	/* sandbox can send characters to stdout before it has a console */
+	if (IS_ENABLED(CONFIG_SANDBOX) && !(gd->flags & GD_FLG_SERIAL_READY)) {
+		os_flush();
+		return;
+	}
+
+	if (IS_ENABLED(CONFIG_DEBUG_UART) && !(gd->flags & GD_FLG_SERIAL_READY))
+		return;
+
+	if (IS_ENABLED(CONFIG_SILENT_CONSOLE) && (gd->flags & GD_FLG_SILENT))
+		return;
+
+	if (IS_ENABLED(CONFIG_DISABLE_CONSOLE) && (gd->flags & GD_FLG_DISABLE_CONSOLE))
+		return;
+
+	if (!gd->have_console)
+		return;
+
+	if (gd->flags & GD_FLG_DEVINIT) {
+		/* Send to the standard output */
+		fflush(stdout);
+	}
+}
+#endif
+
 #ifdef CONFIG_CONSOLE_RECORD
 int console_record_init(void)
 {