diff options
| author | Simon Glass <sjg@chromium.org> | 2016-07-17 01:23:46 -0600 |
|---|---|---|
| committer | Bin Meng <bmeng.cn@gmail.com> | 2016-08-16 11:44:09 +0800 |
| commit | 37b4a9098c44f4dfc951c495bcc3439c2974b1db (patch) | |
| tree | 228a0f55c1d6720b59e7b92ba889a36ab2b930bf /doc | |
| parent | 007adbc2f998258235bb1dc549becfcc22858e99 (diff) | |
x86: Mention running U-Boot in 64-bit mode in the README
This feature is not supported. Document this, and add some details on how it
might be implemented.
Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Diffstat (limited to 'doc')
| -rw-r--r-- | doc/README.x86 | 18 |
1 files changed, 18 insertions, 0 deletions
diff --git a/doc/README.x86 b/doc/README.x86 index 06b3de1011..ba5bb99dcd 100644 --- a/doc/README.x86 +++ b/doc/README.x86 @@ -1049,11 +1049,29 @@ provides the same EFI run-time services) is not currently supported on x86. See README.efi for details of EFI support in U-Boot. +64-bit Support +-------------- +U-Boot supports booting a 64-bit kernel directly and is able to change to +64-bit mode to do so. It also supports (with CONFIG_EFI_STUB) booting from +both 32-bit and 64-bit UEFI. However, U-Boot itself is currently always built +in 32-bit mode. Some access to the full memory range is provided with +arch_phys_memset(). + +The development work to make U-Boot itself run in 64-bit mode has not yet +been attempted. The best approach would likely be to build a 32-bit SPL +image for U-Boot, with CONFIG_SPL_BUILD. This could then handle the early CPU +init in 16-bit and 32-bit mode, running the FSP and any other binaries that +are needed. Then it could change to 64-bit model and jump to U-Boot proper. + +Given U-Boot's extensive 64-bit support this has not been a high priority, +but it would be a nice addition. + TODO List --------- - Audio - Chrome OS verified boot - Support for CONFIG_EFI_LOADER +- Building U-Boot to run in 64-bit mode References ---------- |