lib/tiny-printf.c: Add tiny printf function for space limited environments

This patch adds a small printf() version that supports all basic formats.
Its intented to be used in U-Boot SPL versions on platforms with very
limited internal RAM sizes.

To enable it, just define CONFIG_USE_TINY_PRINTF in your defconfig. This
will result in the SPL using this tiny function and the main U-Boot
still using the full-blown printf() function.

This code was copied from:
http://www.sparetimelabs.com/printfrevisited
With mostly only coding style related changes so that its checkpatch
clean.

The size reduction is about 2.5KiB. Here a comparison for the db-mv784mp-gp
(Marvell AXP) SPL:

Without this patch:
  58963   18536    1928   79427   13643 ./spl/u-boot-spl

With this patch:
  56542   18536    1956   77034   12cea ./spl/u-boot-spl

Note:
To make it possible to compile tiny-printf.c instead of vsprintf.c when
CONFIG_USE_TINY_PRINTF is defined, the functions printf() and vprintf() are
moved from common/console.c into vsprintf.c in this patch.

Signed-off-by: Stefan Roese <sr@denx.de>
Cc: Simon Glass <sjg@chromium.org>
Cc: Hans de Goede <hdegoede@redhat.com>
Cc: Tom Rini <trini@konsulko.com>
Cc: Albert Aribaud <albert.u.boot@aribaud.net>

lib/tiny-printf.c

@@ -0,0 +1,130 @@
+/*
+ * Tiny printf version for SPL
+ *
+ * Copied from:
+ * http://www.sparetimelabs.com/printfrevisited/printfrevisited.php
+ *
+ * Copyright (C) 2004,2008  Kustaa Nyholm
+ *
+ * SPDX-License-Identifier:	LGPL-2.1+
+ */
+
+#include <common.h>
+#include <stdarg.h>
+#include <serial.h>
+
+static char *bf;
+static char buf[12];
+static unsigned int num;
+static char uc;
+static char zs;
+
+static void out(char c)
+{
+	*bf++ = c;
+}
+
+static void out_dgt(char dgt)
+{
+	out(dgt + (dgt < 10 ? '0' : (uc ? 'A' : 'a') - 10));
+	zs = 1;
+}
+
+static void div_out(unsigned int div)
+{
+	unsigned char dgt = 0;
+
+	num &= 0xffff; /* just for testing the code with 32 bit ints */
+	while (num >= div) {
+		num -= div;
+		dgt++;
+	}
+
+	if (zs || dgt > 0)
+		out_dgt(dgt);
+}
+
+int printf(const char *fmt, ...)
+{
+	va_list va;
+	char ch;
+	char *p;
+
+	va_start(va, fmt);
+
+	while ((ch = *(fmt++))) {
+		if (ch != '%') {
+			putc(ch);
+		} else {
+			char lz = 0;
+			char w = 0;
+
+			ch = *(fmt++);
+			if (ch == '0') {
+				ch = *(fmt++);
+				lz = 1;
+			}
+
+			if (ch >= '0' && ch <= '9') {
+				w = 0;
+				while (ch >= '0' && ch <= '9') {
+					w = (((w << 2) + w) << 1) + ch - '0';
+					ch = *fmt++;
+				}
+			}
+			bf = buf;
+			p = bf;
+			zs = 0;
+
+			switch (ch) {
+			case 0:
+				goto abort;
+			case 'u':
+			case 'd':
+				num = va_arg(va, unsigned int);
+				if (ch == 'd' && (int)num < 0) {
+					num = -(int)num;
+					out('-');
+				}
+				div_out(10000);
+				div_out(1000);
+				div_out(100);
+				div_out(10);
+				out_dgt(num);
+				break;
+			case 'x':
+			case 'X':
+				uc = ch == 'X';
+				num = va_arg(va, unsigned int);
+				div_out(0x1000);
+				div_out(0x100);
+				div_out(0x10);
+				out_dgt(num);
+				break;
+			case 'c':
+				out((char)(va_arg(va, int)));
+				break;
+			case 's':
+				p = va_arg(va, char*);
+				break;
+			case '%':
+				out('%');
+			default:
+				break;
+			}
+
+			*bf = 0;
+			bf = p;
+			while (*bf++ && w > 0)
+				w--;
+			while (w-- > 0)
+				putc(lz ? '0' : ' ');
+			while ((ch = *p++))
+				putc(ch);
+		}
+	}
+
+abort:
+	va_end(va);
+	return 0;
+}