diff mbox

[U-Boot,3/3] x86: Mention running U-Boot in 64-bit mode in the README

Message ID 1468740226-27470-3-git-send-email-sjg@chromium.org
State Accepted
Commit 37b4a9098c44f4dfc951c495bcc3439c2974b1db
Delegated to: Bin Meng
Headers show

Commit Message

Simon Glass July 17, 2016, 7:23 a.m. UTC 
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>
---

 doc/README.x86 | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

Comments

Bin Meng July 18, 2016, 1:27 a.m. UTC | #1 
On Sun, Jul 17, 2016 at 3:23 PM, Simon Glass <sjg@chromium.org> wrote:
> 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>
> ---
>
>  doc/README.x86 | 18 ++++++++++++++++++
>  1 file changed, 18 insertions(+)
>

Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Bin Meng July 19, 2016, 3:40 a.m. UTC | #2 
On Mon, Jul 18, 2016 at 9:27 AM, Bin Meng <bmeng.cn@gmail.com> wrote:
> On Sun, Jul 17, 2016 at 3:23 PM, Simon Glass <sjg@chromium.org> wrote:
>> 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>
>> ---
>>
>>  doc/README.x86 | 18 ++++++++++++++++++
>>  1 file changed, 18 insertions(+)
>>
>
> Reviewed-by: Bin Meng <bmeng.cn@gmail.com>

applied to u-boot-x86, thanks!
diff mbox

Patch

diff --git a/doc/README.x86 b/doc/README.x86
index 04e7a54..a2d6994 100644
--- a/doc/README.x86
+++ b/doc/README.x86
@@ -1045,11 +1045,29 @@  provides the same EFI run-time services) is not currently supports 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
 ----------