x86: Move coreboot-table detection into common code

To support detecting booting from coreboot, move the code which locates
the coreboot tables into a common place. Adjust the algorithm slightly to
use a word comparison instead of string, since it is faster.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
[bmeng: correct the comments to 960KB]
Signed-off-by: Bin Meng <bmeng.cn@gmail.com>

arch/x86/cpu/coreboot/tables.c

@@ -115,20 +115,11 @@ __weak void cb_parse_unhandled(u32 tag, unsigned char *ptr)
 
 static int cb_parse_header(void *addr, int len, struct sysinfo_t *info)
 {
+	unsigned char *ptr = addr;
 	struct cb_header *header;
-	unsigned char *ptr = (unsigned char *)addr;
 	int i;
 
-	for (i = 0; i < len; i += 16, ptr += 16) {
+	header = (struct cb_header *)ptr;
-		header = (struct cb_header *)ptr;
-		if (!strncmp((const char *)header->signature, "LBIO", 4))
-			break;
-	}
-
-	/* We walked the entire space and didn't find anything. */
-	if (i >= len)
-		return -1;
-
 	if (!header->table_bytes)
 		return 0;
 
@@ -231,10 +222,13 @@ static int cb_parse_header(void *addr, int len, struct sysinfo_t *info)
 
 int get_coreboot_info(struct sysinfo_t *info)
 {
-	int ret = cb_parse_header((void *)0x00000000, 0x1000, info);
+	long addr;
+	int ret;
 
-	if (ret != 1)
+	addr = locate_coreboot_table();
-		ret = cb_parse_header((void *)0x000f0000, 0x1000, info);
+	if (addr < 0)
+		return addr;
+	ret = cb_parse_header((void *)addr, 0x1000, info);
 
-	return (ret == 1) ? 0 : -1;
+	return ret == 1 ? 0 : -ENOENT;
 }

arch/x86/cpu/i386/cpu.c

@@ -447,6 +447,31 @@ int x86_cpu_init_f(void)
 	return 0;
 }
 
+long detect_coreboot_table_at(ulong start, ulong size)
+{
+	u32 *ptr, *end;
+
+	size /= 4;
+	for (ptr = (void *)start, end = ptr + size; ptr < end; ptr += 4) {
+		if (*ptr == 0x4f49424c) /* "LBIO" */
+			return (long)ptr;
+	}
+
+	return -ENOENT;
+}
+
+long locate_coreboot_table(void)
+{
+	long addr;
+
+	/* We look for LBIO in the first 4K of RAM and again at 960KB */
+	addr = detect_coreboot_table_at(0x0, 0x1000);
+	if (addr < 0)
+		addr = detect_coreboot_table_at(0xf0000, 0x1000);
+
+	return addr;
+}
+
 int x86_cpu_reinit_f(void)
 {
 	setup_identity();

arch/x86/include/asm/coreboot_tables.h

@@ -343,4 +343,11 @@ void *high_table_malloc(size_t bytes);
  */
 void write_coreboot_table(u32 addr, struct memory_area *cfg_tables);
 
+/**
+ * locate_coreboot_table() - Try to find coreboot tables at standard locations
+ *
+ * @return address of table that was found, or -ve error number
+ */
+long locate_coreboot_table(void);
+
 #endif