On 24/05/2021 18:42, François Ozog wrote:
Hi,

I verified that RPI4 can boot Ubuntu and LEDGE RP with UEFI + U-Boot.
Two flows have been checked: direct (kernel+initrd in BootXXX variable
leveraging LOAD_FILE2 mechanism) and through grub.

Note: Grub (current head) behaves properly but does not display anything on
serial console because lack of U-Boot (2021.07-rc2) support for:

   GRUB_EFI_SERIAL_IO_GUID \

   { 0xbb25cf6f, 0xf1d4, 0x11d2, \

     { 0x9a, 0x0c, 0x00, 0x90, 0x27, 0x3f, 0xc1, 0xfd } \

   }


/* details: grub-core/term/efi/serial.c, grub_efiserial_init() ->
grub_efi_locate_handle
(GRUB_EFI_BY_PROTOCOL, &serial_io_guid,...) returns NULL */

This doesn't look right to me. U-Boot provides the SimpleTextProtocol
which Grub can use to display the menu over either UART or framebuffer.
The SERIAL_IO protocol is not required. If you aren't getting output on
the serial console then it is more likely a U-Boot configuration problem
rather than missing functionality.

g.



So I think we need to add this protocol and some others to make the UEFI
text environment fully supported for grub.


Cheers


FF


PS: It would be nice to have an efidebug command to actually trace all boot
services calls to "get_protocol" and either trace all requests or just
failed requests.


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