diff options
Diffstat (limited to 'arch/i386')
| -rw-r--r-- | arch/i386/cpu/start.S | 36 | ||||
| -rw-r--r-- | arch/i386/cpu/start16.S | 8 |
2 files changed, 38 insertions, 6 deletions
diff --git a/arch/i386/cpu/start.S b/arch/i386/cpu/start.S index 1980f1a7b7..3cea04b4ce 100644 --- a/arch/i386/cpu/start.S +++ b/arch/i386/cpu/start.S @@ -33,7 +33,27 @@ .type _start, @function .globl _i386boot_start _i386boot_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) + */ + cli + cld + + /* Turn of cache (this might require a 486-class CPU) */ + movl %cr0, %eax + orl $0x60000000,%eax + movl %eax, %cr0 + wbinvd + + /* Tell 32-bit code it is being entered from an in-RAM copy */ + movw $0x0000, %bx _start: + /* This is the 32-bit cold-reset entry point */ + movl $0x18,%eax /* Load our segement registes, the * gdt have already been loaded by start16.S */ movw %ax,%fs @@ -42,6 +62,18 @@ _start: movw %ax,%es movw %ax,%ss + /* Clear the interupt vectors */ + lidt blank_idt_ptr + + /* + * Skip low-level board and memory initialization if not starting + * from cold-reset. This allows us to do a fail safe boot-strap + * into a new build of U-Boot from a known-good boot flash + */ + movw $0x0001, %ax + cmpw %ax, %bx + jne mem_init_ret + /* We call a few functions in the board support package * since we have no stack yet we'll have to use %ebp * to store the return address */ @@ -138,3 +170,7 @@ stack_ok: die: hlt jmp die hlt + +blank_idt_ptr: + .word 0 /* limit */ + .long 0 /* base */ diff --git a/arch/i386/cpu/start16.S b/arch/i386/cpu/start16.S index 1ebb6bc8b6..5e33aa1069 100644 --- a/arch/i386/cpu/start16.S +++ b/arch/i386/cpu/start16.S @@ -45,10 +45,8 @@ board_init16_ret: wbinvd /* load the descriptor tables */ -o32 cs lidt idt_ptr o32 cs lgdt gdt_ptr - /* Now, we enter protected mode */ movl %cr0, %eax orl $1,%eax @@ -57,6 +55,8 @@ o32 cs lgdt gdt_ptr /* Flush the prefetch queue */ jmp ff ff: + /* Tell 32-bit code it is being entered from hard-reset */ + movw $0x0001, %bx /* Finally jump to the 32bit initialization code */ movw $code32start, %ax @@ -68,10 +68,6 @@ code32start: .long _start /* offset */ .word 0x10 /* segment */ -idt_ptr: - .word 0 /* limit */ - .long 0 /* base */ - gdt_ptr: .word 0x30 /* limit (48 bytes = 6 GDT entries) */ .long BOOT_SEG + gdt /* base */ |