[U-Boot] [PATCH 00/82] x86: Add initial support for 64-bit U-Boot

[Bin Meng]

Hi Simon,

On Mon, Sep 26, 2016 at 11:33 AM, Simon Glass <sjg at chromium.org> wrote:
> At present U-Boot runs entirely in 32-bit mode on x86, except for the
> initial switch from 16-bit mode. On 64-bit machines it is possible to run
> in 64-bit mode. This series starts the process of adding this support.
>
> The main benefit of 64-bit mode for a boot loader is direct access to all
> available memory. There are also more registers, but this makes very little
> difference.
>
> This feature is implemented by putting all of the 32-bit code in an SPL
> build. SPL then runs through all the init that has to be done in 32-bit
> mode, changes to 64-bit mode and then jumps to U-Boot proper.
>
> Typically the total code size increases slightly. For example, on link in
> 32-bit mode, U-Boot has around 480KB of code (admittedly with a large
> number of features enabled). In 64-bit mode, U-Boot falls to around 460KB,
> but SPL adds another 60KB, for a net increase of 40KB. Partly this is due
> to code duplication and partly it is due to the worse code density of
> 64-bit code on x86.
>
> Many major features are not implemented yet, for example:
> - SDRAM sizing
> - Booting linux
> - FSP support
> - EFI support
> - SCSI device init
> - Running video ROMs
>
> Still, this is a big step forward towards full 64-bit support. To enable it,
> select CONFIG_X86_RUN_64BIT.
>
> This series is available at u-boot-x86/64-working
>

Looks it requires a 64-bit toolchain to compile 64-bit U-Boot. For
example, I used kernel.org i386 toolchain to compile 64-bit U-Boot, I
got:

include/asm-generic/bitops/__fls.h: In function '__fls':
include/asm-generic/bitops/__fls.h:17:2: warning: left shift count >=
width of type
  if (!(word & (~0ul << 32))) {
  ^
include/asm-generic/bitops/__fls.h:19:3: warning: left shift count >=
width of type
   word <<= 32;
   ^
include/asm-generic/bitops/__fls.h:22:2: warning: left shift count >=
width of type
  if (!(word & (~0ul << (BITS_PER_LONG-16)))) {
  ^
include/asm-generic/bitops/__fls.h:26:2: warning: left shift count >=
width of type
  if (!(word & (~0ul << (BITS_PER_LONG-8)))) {
  ^
include/asm-generic/bitops/__fls.h:30:2: warning: left shift count >=
width of type
  if (!(word & (~0ul << (BITS_PER_LONG-4)))) {
  ^
include/asm-generic/bitops/__fls.h:34:2: warning: left shift count >=
width of type
  if (!(word & (~0ul << (BITS_PER_LONG-2)))) {
  ^
include/asm-generic/bitops/__fls.h:38:2: warning: left shift count >=
width of type
  if (!(word & (~0ul << (BITS_PER_LONG-1))))
  ^
arch/x86/cpu/intel_common/microcode.c: In function 'microcode_read_rev':
arch/x86/cpu/intel_common/microcode.c:79:2: error: PIC register
clobbered by 'ebx' in 'asm'
  asm volatile (
  ^
make[2]: *** [arch/x86/cpu/intel_common/microcode.o] Error 1

After I switched to 64-bit toolchain from kernel.org (x86_64-linux),
there was no such warnings/errors, but I still got build failure at
last.

  ./tools/binman/binman -d u-boot.dtb -O . -I . -I
./board/google/chromebook_link u-boot-x86-16bit.bin
Traceback (most recent call last):
  File "./tools/binman/binman", line 31, in <module>
    import control
  File "./tools/binman/control.py", line 17, in <module>
    from image import Image
  File "./tools/binman/image.py", line 12, in <module>
    import entry
  File "./tools/binman/etype/entry.py", line 8, in <module>
    import importlib
ImportError: No module named importlib
make: *** [u-boot.rom] Error 1

Regards,
Bin