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x86: Add various minor tidy-ups to the 32-bit startup code

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Fix a typo, improve some comments and add a little more detail in some
cases.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
This commit is contained in:
Simon Glass 2015-07-31 09:31:25 -06:00
parent 5598facbd2
commit da3a95d60b
1 changed files with 26 additions and 20 deletions
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46
arch/x86/cpu/start.S
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@ -25,11 +25,11 @@
.globl _x86boot_start
_x86boot_start:
/*
* This is the fail safe 32-bit bootstrap entry point. The
* following code is not executed from a cold-reset (actually, a
* lot of it is, but from real-mode after cold reset. It is
* repeated here to put the board into a state as close to cold
* reset as necessary)
* This is the fail-safe 32-bit bootstrap entry point.
*
* This code is used when booting from another boot loader like
* coreboot or EFI. So we repeat some of the same init found in
* start16.
*/
cli
cld
@ -45,15 +45,15 @@ _x86boot_start:
jmp 1f
_start:
/*
* This is the 32-bit cold-reset entry point. Initialize %bx to 0
* in case we're preceeded by some sort of boot stub.
* This is the 32-bit cold-reset entry point, coming from start16.
* Set %bx to 0 to indicate this.
*/
movw $GD_FLG_COLD_BOOT, %bx
1:
/* Save BIST */
movl %eax, %ebp
/* Load the segement registes to match the gdt loaded in start16.S */
/* Load the segement registers to match the GDT loaded in start16.S */
movl $(X86_GDT_ENTRY_32BIT_DS * X86_GDT_ENTRY_SIZE), %eax
movw %ax, %fs
movw %ax, %ds
@ -64,7 +64,11 @@ _start:
/* Clear the interrupt vectors */
lidt blank_idt_ptr
/* Early platform init (setup gpio, etc ) */
/*
* Critical early platform init - generally not used, we prefer init
* to happen later when we have a console, in case something goes
* wrong.
*/
jmp early_board_init
.globl early_board_init_ret
early_board_init_ret:
@ -79,7 +83,7 @@ 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. The MRC requires some space at the top.
* and early malloc() area. The MRC requires some space at the top.
*
* Stack grows down from top of CAR. We have:
*
@ -97,7 +101,7 @@ car_init_ret:
#endif
#else
/*
* When we get here after car_init, esp points to a temporary stack
* When we get here after car_init(), esp points to a temporary stack
* and esi holds the HOB list address returned by the FSP.
*/
#endif
@ -137,17 +141,18 @@ skip_hob:
movl %esp, %ecx
#if defined(CONFIG_SYS_MALLOC_F_LEN)
/* Set up the pre-relocation malloc pool */
subl $CONFIG_SYS_MALLOC_F_LEN, %esp
movl %eax, %edx
addl $GD_MALLOC_BASE, %edx
movl %esp, (%edx)
#endif
/* Store BIST */
/* Store BIST into global_data */
movl %eax, %edx
addl $GD_BIST, %edx
movl %ebp, (%edx)
/* Set second parameter to setup_gdt */
/* Set second parameter to setup_gdt() */
movl %ecx, %edx
/* Setup global descriptor table so gd->xyz works */
@ -157,7 +162,7 @@ skip_hob:
post_code(POST_START_DONE)
xorl %eax, %eax
/* Enter, U-boot! */
/* Enter, U-Boot! */
call board_init_f
/* indicate (lack of) progress */
@ -184,13 +189,13 @@ board_init_f_r_trampoline:
/* Align global data to 16-byte boundary */
andl $0xfffffff0, %esp
/* Setup first parameter to memcpy (and setup_gdt) */
/* Setup first parameter to memcpy() and setup_gdt() */
movl %esp, %eax
/* Setup second parameter to memcpy */
/* Setup second parameter to memcpy() */
fs movl 0, %edx
/* Set third parameter to memcpy */
/* Set third parameter to memcpy() */
movl $GENERATED_GBL_DATA_SIZE, %ecx
/* Copy global data from CAR to SDRAM stack */
@ -202,7 +207,7 @@ board_init_f_r_trampoline:
/* Align global descriptor table to 16-byte boundary */
andl $0xfffffff0, %esp
/* Set second parameter to setup_gdt */
/* Set second parameter to setup_gdt() */
movl %esp, %edx
/* Setup global descriptor table so gd->xyz works */
@ -216,7 +221,7 @@ board_init_f_r_trampoline:
call car_uninit
1:
/* Re-enter U-Boot by calling board_init_f_r */
/* Re-enter U-Boot by calling board_init_f_r() */
call board_init_f_r
die:
@ -230,9 +235,10 @@ blank_idt_ptr:
.p2align 2 /* force 4-byte alignment */
/* Add a multiboot header so U-Boot can be loaded by GRUB2 */
multiboot_header:
/* magic */
.long 0x1BADB002
.long 0x1badb002
/* flags */
.long (1 << 16)
/* checksum */