x86: make LOAD_FROM_32_BIT visible for platforms

This option is useful not only for development, but for the platforms
where U-Boot is run from custom ROM bootloader. For example, Intel
Edison is that board.

Make this option visible that platforms can select it if needed.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 675b56f617e1b07f9ed9a00eb24efe8df08cbb85..5f9597b230fe6b7b0abe7aec7a142ec7a7eff80f 100644 (file)
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -195,6 +195,14 @@ config SYS_X86_START16
        depends on X86_RESET_VECTOR
        default 0xfffff800
 
+config X86_LOAD_FROM_32_BIT
+       bool "Boot from a 32-bit program"
+       help
+         Define this to boot U-Boot from a 32-bit program which sets
+         the GDT differently. This can be used to boot directly from
+         any stage of coreboot, for example, bypassing the normal
+         payload-loading feature.
+
 config BOARD_ROMSIZE_KB_512
        bool
 config BOARD_ROMSIZE_KB_1024

diff --git a/arch/x86/cpu/start.S b/arch/x86/cpu/start.S
index a5cba1cf2a766680e3e1b8ab6290bee2aa8a0191..8de55a0af1de3681a360ff35fb5acf70ef878a90 100644 (file)
--- a/arch/x86/cpu/start.S
+++ b/arch/x86/cpu/start.S
@@ -18,14 +18,6 @@
 #include <generated/generic-asm-offsets.h>
 #include <generated/asm-offsets.h>
 
-/*
- * Define this to boot U-Boot from a 32-bit program which sets the GDT
- * differently. This can be used to boot directly from any stage of coreboot,
- * for example, bypassing the normal payload-loading feature.
- * This is only useful for development.
- */
-#undef LOAD_FROM_32_BIT
-
 .section .text
 .code32
 .globl _start
@@ -76,7 +68,7 @@ _start:
        /* Save table pointer */
        movl    %ecx, %esi
 
-#ifdef LOAD_FROM_32_BIT
+#ifdef CONFIG_X86_LOAD_FROM_32_BIT
        lgdt    gdt_ptr2
 #endif
 
@@ -233,7 +225,7 @@ multiboot_header:
        /* entry addr */
        .long   CONFIG_SYS_TEXT_BASE
 
-#ifdef LOAD_FROM_32_BIT
+#ifdef CONFIG_X86_LOAD_FROM_32_BIT
        /*
         * The following Global Descriptor Table is just enough to get us into
         * 'Flat Protected Mode' - It will be discarded as soon as the final