Hi Alex,
On Mon, Jun 11, 2018 at 3:34 PM, Alexander Graf agraf@suse.de wrote:
On 06/11/2018 08:01 AM, Bin Meng wrote:
Hi Alex,
On Mon, Jun 11, 2018 at 1:52 PM, Alexander Graf agraf@suse.de wrote:
On 11.06.18 01:29, Bin Meng wrote:
On Mon, Jun 11, 2018 at 3:16 AM, Alexander Graf agraf@suse.de wrote:
On 10.06.18 15:25, Bin Meng wrote:
If UEFI BIOS has the graphics output protocol (GOP), let's pass its information to U-Boot payload so that U-Boot can utilize it (eg: an EFI framebuffer driver).
Signed-off-by: Bin Meng bmeng.cn@gmail.com
Why can't the FB drive determine all of this on its own and just fail probe if no GOP protocol can be found?
It cannot. Once U-Boot payload is running, the boot services are gone. There is no way to determine the GOP protocol.
Interesting. Is there a particular reason you're not preserving boot services?
This is EFI payload support with CONFIG_EFI_STUB. Preserving boot services is EFI application, with CONFIG_EFI_APP. For example, see serial_efi.c which is the serial driver that uses EFI's boot services to output characters on the serial port.
Oh, I see. That makes sense now.
Do people actually need CONFIG_EFI_STUB then?
I think you wanted to say: Do people actually need CONFIG_EFI_APP then? CONFIG_EFI_STUB is more useful than CONFIG_EFI_APP. The application support is very limited.
As the README.u-boot_on_efi says:
Running U-Boot on EFI is useful in several situations:
- You have EFI running on a board but U-Boot does not natively support it fully yet. You can boot into U-Boot from EFI and use that until U-Boot is fully ported
- You need to use an EFI implementation (e.g. UEFI) because your vendor requires it in order to provide support
- You plan to use coreboot to boot into U-Boot but coreboot support does not currently exist for your platform. In the meantime you can use U-Boot on EFI and then move to U-Boot on coreboot when ready
- You use EFI but want to experiment with a simpler alternative like U-Boot
Right now, I have one Intel SkyLake board, and before I get a native U-Boot up and running as the 1st stage bootloader on this board, I can run U-Boot as the EFI payload to experiment something, which is very handy.
It might be quite handy to reuse UEFI block interfaces for example. It might also be useful to preserve (parts of?) the memory map so we don't overwrite random SMM code for example.
Maybe I misunderstand the purpose of the UEFI U-Boot support though ;).
Looks there is some misunderstanding around the EFI payload support.
Yes, I have to admit that I never really cared enough about it to read its documentation though :).
Yep, this sometimes confuses people :)
Regards, Bin