x86: Add Kconfig options to build 64-bit U-Boot

Add a new CONFIG_X86_64 option which will eventually cause U-Boot to be
built as a 64-bit application, with SPL doing the 16/32-bit init.

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

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 0884af22a79edf3b245fb1c1c8a39d9eb871f1eb..5cd58d450b51d3a62b3c969301d03c28711bd843 100644 (file)
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -4,6 +4,52 @@ menu "x86 architecture"
 config SYS_ARCH
        default "x86"
 
+choice
+       prompt "Run U-Boot in 32/64-bit mode"
+       default X86_RUN_32BIT
+       help
+         U-Boot can be built as a 32-bit binary which runs in 32-bit mode
+         even on 64-bit machines. In this case SPL is not used, and U-Boot
+         runs directly from the reset vector (via 16-bit start-up).
+
+         Alternatively it can be run as a 64-bit binary, thus requiring a
+         64-bit machine. In this case SPL runs in 32-bit mode (via 16-bit
+         start-up) then jumps to U-Boot in 64-bit mode.
+
+         For now, 32-bit mode is recommended, as 64-bit is still
+         experimental and is missing a lot of features.
+
+config X86_RUN_32BIT
+       bool "32-bit"
+       help
+         Build U-Boot as a 32-bit binary with no SPL. This is the currently
+         supported normal setup. U-Boot will stay in 32-bit mode even on
+         64-bit machines. When booting a 64-bit kernel, U-Boot will switch
+         to 64-bit just before starting the kernel. Only the bottom 4GB of
+         memory can be accessed through normal means, although
+         arch_phys_memset() can be used for basic access to other memory.
+
+config X86_RUN_64BIT
+       bool "64-bit"
+       select X86_64
+       select SUPPORT_SPL
+       select SPL
+       select SPL_SEPARATE_BSS
+       help
+         Build U-Boot as a 64-bit binary with a 32-bit SPL. This is
+         experimental and many features are missing. U-Boot SPL starts up,
+         runs through the 16-bit and 32-bit init, then switches to 64-bit
+         mode and jumps to U-Boot proper.
+
+endchoice
+
+config X86_64
+       bool
+
+config SPL_X86_64
+       bool
+       depends on SPL
+
 choice
        prompt "Mainboard vendor"
        default VENDOR_EMULATION