console: Implement pre-console buffer

Allow redirection of console output prior to console initialisation to a
temporary buffer.

To enable this functionality, the board (or arch) must define:
 - CONFIG_PRE_CONSOLE_BUFFER - Enable pre-console buffer
 - CONFIG_PRE_CON_BUF_ADDR - Base address of pre-console buffer
 - CONFIG_PRE_CON_BUF_SZ - Size of pre-console buffer (in bytes)

The pre-console buffer will buffer the last CONFIG_PRE_CON_BUF_SZ bytes
Any earlier characters are silently dropped.

README

@@ -619,6 +619,20 @@ The following options need to be configured:
 		must be defined, to setup the maximum idle timeout for
 		the SMC.
 
+- Pre-Console Buffer:
+                Prior to the console being initialised (i.e. serial UART
+                initialised etc) all console output is silently discarded.
+                Defining CONFIG_PRE_CONSOLE_BUFFER will cause U-Boot to
+                buffer any console messages prior to the console being
+                initialised to a buffer of size CONFIG_PRE_CON_BUF_SZ
+                bytes located at CONFIG_PRE_CON_BUF_ADDR. The buffer is
+                a circular buffer, so if more than CONFIG_PRE_CON_BUF_SZ
+                bytes are output before the console is  initialised, the
+                earlier bytes are discarded.
+
+                'Sane' compilers will generate smaller code if
+                CONFIG_PRE_CON_BUF_SZ is a power of 2
+
 - Boot Delay:	CONFIG_BOOTDELAY - in seconds
 		Delay before automatically booting the default image;
 		set to -1 to disable autoboot.

arch/arm/include/asm/global_data.h

@@ -38,6 +38,9 @@ typedef	struct	global_data {
 	unsigned long	flags;
 	unsigned long	baudrate;
 	unsigned long	have_console;	/* serial_init() was called */
+#ifdef CONFIG_PRE_CONSOLE_BUFFER
+	unsigned long	precon_buf_idx;	/* Pre-Console buffer index */
+#endif
 	unsigned long	env_addr;	/* Address  of Environment struct */
 	unsigned long	env_valid;	/* Checksum of Environment valid? */
 	unsigned long	fb_base;	/* base address of frame buffer */

arch/avr32/include/asm/global_data.h

@@ -38,6 +38,9 @@ typedef	struct	global_data {
 	unsigned long	baudrate;
 	unsigned long	stack_end;	/* highest stack address */
 	unsigned long	have_console;	/* serial_init() was called */
+#ifdef CONFIG_PRE_CONSOLE_BUFFER
+	unsigned long	precon_buf_idx;	/* Pre-Console buffer index */
+#endif
 	unsigned long	reloc_off;	/* Relocation Offset */
 	unsigned long	env_addr;	/* Address of env struct */
 	unsigned long	env_valid;	/* Checksum of env valid? */

arch/blackfin/include/asm/global_data.h

@@ -45,6 +45,9 @@ typedef struct global_data {
 	unsigned long board_type;
 	unsigned long baudrate;
 	unsigned long have_console;	/* serial_init() was called */
+#ifdef CONFIG_PRE_CONSOLE_BUFFER
+	unsigned long	precon_buf_idx;	/* Pre-Console buffer index */
+#endif
 	phys_size_t ram_size;		/* RAM size */
 	unsigned long env_addr;	/* Address  of Environment struct */
 	unsigned long env_valid;	/* Checksum of Environment valid? */

arch/m68k/include/asm/global_data.h

@@ -57,6 +57,9 @@ typedef	struct	global_data {
 	unsigned long	env_addr;	/* Address  of Environment struct	*/
 	unsigned long	env_valid;	/* Checksum of Environment valid?	*/
 	unsigned long	have_console;	/* serial_init() was called		*/
+#ifdef CONFIG_PRE_CONSOLE_BUFFER
+	unsigned long	precon_buf_idx;	/* Pre-Console buffer index */
+#endif
 #if defined(CONFIG_LCD) || defined(CONFIG_VIDEO)
 	unsigned long	fb_base;	/* Base addr of framebuffer memory */
 #endif

arch/microblaze/include/asm/global_data.h

@@ -39,6 +39,9 @@ typedef	struct	global_data {
 	unsigned long	flags;
 	unsigned long	baudrate;
 	unsigned long	have_console;	/* serial_init() was called */
+#ifdef CONFIG_PRE_CONSOLE_BUFFER
+	unsigned long	precon_buf_idx;	/* Pre-Console buffer index */
+#endif
 	unsigned long	env_addr;	/* Address  of Environment struct */
 	unsigned long	env_valid;	/* Checksum of Environment valid? */
 	unsigned long	fb_base;	/* base address of frame buffer */

arch/mips/include/asm/global_data.h

@@ -41,6 +41,9 @@ typedef	struct	global_data {
 	unsigned long	flags;
 	unsigned long	baudrate;
 	unsigned long	have_console;	/* serial_init() was called */
+#ifdef CONFIG_PRE_CONSOLE_BUFFER
+	unsigned long	precon_buf_idx;	/* Pre-Console buffer index */
+#endif
 	phys_size_t	ram_size;	/* RAM size */
 	unsigned long	reloc_off;	/* Relocation Offset */
 	unsigned long	env_addr;	/* Address  of Environment struct */

arch/nios2/include/asm/global_data.h

@@ -29,6 +29,9 @@ typedef	struct	global_data {
 	unsigned long	baudrate;
 	unsigned long	cpu_clk;	/* CPU clock in Hz!		*/
 	unsigned long	have_console;	/* serial_init() was called */
+#ifdef CONFIG_PRE_CONSOLE_BUFFER
+	unsigned long	precon_buf_idx;	/* Pre-Console buffer index */
+#endif
 	phys_size_t	ram_size;	/* RAM size */
 	unsigned long	env_addr;	/* Address  of Environment struct */
 	unsigned long	env_valid;	/* Checksum of Environment valid */

arch/powerpc/include/asm/global_data.h

@@ -138,6 +138,9 @@ typedef	struct	global_data {
 	unsigned long	env_addr;	/* Address  of Environment struct	*/
 	unsigned long	env_valid;	/* Checksum of Environment valid?	*/
 	unsigned long	have_console;	/* serial_init() was called		*/
+#ifdef CONFIG_PRE_CONSOLE_BUFFER
+	unsigned long	precon_buf_idx;	/* Pre-Console buffer index */
+#endif
 #if defined(CONFIG_SYS_ALLOC_DPRAM) || defined(CONFIG_CPM2)
 	unsigned int	dp_alloc_base;
 	unsigned int	dp_alloc_top;

arch/sh/include/asm/global_data.h

@@ -34,6 +34,9 @@ typedef	struct global_data
 	unsigned long	baudrate;
 	unsigned long	cpu_clk;	/* CPU clock in Hz! */
 	unsigned long	have_console;	/* serial_init() was called */
+#ifdef CONFIG_PRE_CONSOLE_BUFFER
+	unsigned long	precon_buf_idx;	/* Pre-Console buffer index */
+#endif
 	phys_size_t	ram_size;	/* RAM size */
 	unsigned long	env_addr;	/* Address  of Environment struct */
 	unsigned long	env_valid;	/* Checksum of Environment valid */

arch/sparc/include/asm/global_data.h

@@ -53,6 +53,9 @@ typedef struct global_data {
 	unsigned long env_valid;	/* Checksum of Environment valid?       */
 	unsigned long have_console;	/* serial_init() was called */
 
+#ifdef CONFIG_PRE_CONSOLE_BUFFER
+	unsigned long	precon_buf_idx;	/* Pre-Console buffer index */
+#endif
 #if defined(CONFIG_LCD) || defined(CONFIG_VIDEO)
 	unsigned long fb_base;	/* Base address of framebuffer memory   */
 #endif

arch/x86/include/asm/global_data.h

@@ -40,6 +40,9 @@ typedef	struct global_data {
 	unsigned long	flags;
 	unsigned long	baudrate;
 	unsigned long	have_console;	/* serial_init() was called */
+#ifdef CONFIG_PRE_CONSOLE_BUFFER
+	unsigned long	precon_buf_idx;	/* Pre-Console buffer index */
+#endif
 	unsigned long	reloc_off;	/* Relocation Offset */
 	unsigned long	load_off;	/* Load Offset */
 	unsigned long	env_addr;	/* Address  of Environment struct */

common/console.c

@@ -329,6 +329,39 @@ int tstc(void)
 	return serial_tstc();
 }
 
+#ifdef CONFIG_PRE_CONSOLE_BUFFER
+#define CIRC_BUF_IDX(idx) ((idx) % (unsigned long)CONFIG_PRE_CON_BUF_SZ)
+
+static void pre_console_putc(const char c)
+{
+	char *buffer = (char *)CONFIG_PRE_CON_BUF_ADDR;
+
+	buffer[CIRC_BUF_IDX(gd->precon_buf_idx++)] = c;
+}
+
+static void pre_console_puts(const char *s)
+{
+	while (*s)
+		pre_console_putc(*s++);
+}
+
+static void print_pre_console_buffer(void)
+{
+	unsigned long i = 0;
+	char *buffer = (char *)CONFIG_PRE_CON_BUF_ADDR;
+
+	if (gd->precon_buf_idx > CONFIG_PRE_CON_BUF_SZ)
+		i = gd->precon_buf_idx - CONFIG_PRE_CON_BUF_SZ;
+
+	while (i < gd->precon_buf_idx)
+		putc(buffer[CIRC_BUF_IDX(i++)]);
+}
+#else
+static inline void pre_console_putc(const char c) {}
+static inline void pre_console_puts(const char *s) {}
+static inline void print_pre_console_buffer(void) {}
+#endif
+
 void putc(const char c)
 {
 #ifdef CONFIG_SILENT_CONSOLE
@@ -342,7 +375,7 @@ void putc(const char c)
 #endif
 
 	if (!gd->have_console)
-		return;
+		return pre_console_putc(c);
 
 	if (gd->flags & GD_FLG_DEVINIT) {
 		/* Send to the standard output */
@@ -366,7 +399,7 @@ void puts(const char *s)
 #endif
 
 	if (!gd->have_console)
-		return;
+		return pre_console_puts(s);
 
 	if (gd->flags & GD_FLG_DEVINIT) {
 		/* Send to the standard output */
@@ -383,8 +416,10 @@ int printf(const char *fmt, ...)
 	uint i;
 	char printbuffer[CONFIG_SYS_PBSIZE];
 
+#ifndef CONFIG_PRE_CONSOLE_BUFFER
 	if (!gd->have_console)
 		return 0;
+#endif
 
 	va_start(args, fmt);
 
@@ -404,8 +439,10 @@ int vprintf(const char *fmt, va_list args)
 	uint i;
 	char printbuffer[CONFIG_SYS_PBSIZE];
 
+#ifndef CONFIG_PRE_CONSOLE_BUFFER
 	if (!gd->have_console)
 		return 0;
+#endif
 
 	/* For this to work, printbuffer must be larger than
 	 * anything we ever want to print.
@@ -547,6 +584,8 @@ int console_init_f(void)
 		gd->flags |= GD_FLG_SILENT;
 #endif
 
+	print_pre_console_buffer();
+
 	return 0;
 }