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doc: update UEFI documentation

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* UEFI variables can be persisted
* describe that the sequence of files loaded before bootefi matters

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
This commit is contained in:
Heinrich Schuchardt
2020-08-16 12:27:19 +02:00
parent dd12c6a446
commit ebcbfc7d6d
1 changed files with 8 additions and 4 deletions
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12
doc/uefi/uefi.rst
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@@ -59,6 +59,10 @@ Below you find the output of an example session starting GRUB::
120832 bytes read in 7 ms (16.5 MiB/s)
=> bootefi ${kernel_addr_r} ${fdt_addr_r}
The bootefi command uses the device, the file name, and the file size
(environment variable 'filesize') of the most recently loaded file when setting
up the binary for execution. So the UEFI binary should be loaded last.
The environment variable 'bootargs' is passed as load options in the UEFI system
table. The Linux kernel EFI stub uses the load options as command line
arguments.
@@ -217,13 +221,13 @@ which has to be enabled via CONFIG_SUPPORT_EMMC_RPMB=y.
Executing the boot manager
~~~~~~~~~~~~~~~~~~~~~~~~~~
The UEFI specification foresees to define boot entries and boot sequence via UEFI
variables. Booting according to these variables is possible via::
The UEFI specification foresees to define boot entries and boot sequence via
UEFI variables. Booting according to these variables is possible via::
bootefi bootmgr [fdt address]
As of U-Boot v2018.03 UEFI variables are not persisted and cannot be set at
runtime.
As of U-Boot v2020.10 UEFI variables cannot be set at runtime. The U-Boot
command 'efidebug' can be used to set the variables.
Executing the built in hello world application
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~