x86: Save the BIST value on reset

The built in self test value is available in register eax on start-up. Save
it so that it can be accessed later. Unfortunately we must wait until the
global_data is available before we can do this, so there is a little bit of
shuffling to keep it around.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>

arch/x86/cpu/start.S

@@ -49,6 +49,8 @@ _start:
 	 */
 	movw	$GD_FLG_COLD_BOOT, %bx
 1:
+	/* Save BIST */
+	movl	%eax, %ebp
 
 	/* Load the segement registes to match the gdt loaded in start16.S */
 	movl	$(X86_GDT_ENTRY_32BIT_DS * X86_GDT_ENTRY_SIZE), %eax
@@ -117,9 +119,10 @@ car_init_ret:
 	addl	$GD_MALLOC_BASE, %edx
 	movl	%esp, (%edx)
 #endif
-
-	/* Align temporary global descriptor table to 16-byte boundary */
-	andl	$0xfffffff0, %esp
+	/* Store BIST */
+	movl	%eax, %edx
+	addl	$GD_BIST, %edx
+	movl	%ebp, (%edx)
 
 	/* Set second parameter to setup_gdt */
 	movl	%ecx, %edx

arch/x86/cpu/start16.S

@@ -21,6 +21,9 @@
 .code16
 .globl start16
 start16:
+	/* Save BIST */
+	movl	%eax, %ecx
+
 	/* Set the Cold Boot / Hard Reset flag */
 	movl	$GD_FLG_COLD_BOOT, %ebx
 
@@ -45,9 +48,11 @@ o32 cs	lgdt	gdt_ptr
 	/* Flush the prefetch queue */
 	jmp	ff
 ff:
-	/* Finally jump to the 32bit initialization code */
+
+	/* Finally restore BIST and jump to the 32bit initialization code */
 	movw	$code32start, %ax
 	movw	%ax, %bp
+	movl	%ecx, %eax
 o32 cs	ljmp	*(%bp)
 
 	/* 48-bit far pointer */

arch/x86/include/asm/global_data.h

@@ -17,6 +17,7 @@ struct arch_global_data {
 	uint32_t tsc_base_kclocks;	/* Initial tsc as a kclocks value */
 	uint32_t tsc_prev;		/* For show_boot_progress() */
 	void *new_fdt;			/* Relocated FDT */
+	uint32_t bist;			/* Built-in self test value */
 };
 
 #endif

lib/asm-offsets.c

@@ -31,6 +31,9 @@ int main(void)
 #ifdef CONFIG_SYS_MALLOC_F_LEN
 	DEFINE(GD_MALLOC_BASE, offsetof(struct global_data, malloc_base));
 #endif
+#ifdef CONFIG_X86
+	DEFINE(GD_BIST, offsetof(struct global_data, arch.bist));
+#endif
 
 #if defined(CONFIG_ARM)