x86: Tidy up global descriptor table setup

This code is a little muddled, so tidy it up. Make sure that we put the
GDT in the right place and set it up properly.

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

diff --git a/arch/x86/cpu/start.S b/arch/x86/cpu/start.S
index 338bab19e471fdd3f4ab088aa999afeb2e10145e..781d32447ba6c53a5fe50cc341b88c36f0be870d 100644 (file)
--- a/arch/x86/cpu/start.S
+++ b/arch/x86/cpu/start.S
@@ -74,6 +74,16 @@ car_init_ret:
         * We now have CONFIG_SYS_CAR_SIZE bytes of Cache-As-RAM (or SRAM,
         * or fully initialised SDRAM - we really don't care which)
         * starting at CONFIG_SYS_CAR_ADDR to be used as a temporary stack
+        * and early malloc area.
+        *
+        * Stack grows down from top of CAR. We have:
+        *
+        * top-> CONFIG_SYS_CAR_ADDR + CONFIG_SYS_CAR_SIZE
+        *      global_data
+        *      x86 global descriptor table
+        *      early malloc area
+        *      stack
+        * bottom-> CONFIG_SYS_CAR_ADDR
         */
 
        /* Stack grows down from top of CAR */
@@ -91,12 +101,16 @@ car_init_ret:
        movl    %esp, %edi
        rep     stosb
 
-       /* Setup first parameter to setup_gdt */
+       /* Setup first parameter to setup_gdt, pointer to global_data */
        movl    %esp, %eax
 
        /* Reserve space for global descriptor table */
        subl    $X86_GDT_SIZE, %esp
 
+       /* Align temporary global descriptor table to 16-byte boundary */
+       andl    $0xfffffff0, %esp
+       movl    %esp, %ecx
+
 #if defined(CONFIG_SYS_MALLOC_F_LEN)
        subl    $CONFIG_SYS_MALLOC_F_LEN, %esp
        movl    %eax, %edx
@@ -108,14 +122,13 @@ car_init_ret:
        andl    $0xfffffff0, %esp
 
        /* Set second parameter to setup_gdt */
-       movl    %esp, %edx
+       movl    %ecx, %edx
 
        /* Setup global descriptor table so gd->xyz works */
        call    setup_gdt
 
        /* Set parameter to board_init_f() to boot flags */
        xorl    %eax, %eax
-       movw    %bx, %ax
 
        /* Enter, U-boot! */
        call    board_init_f