u-boot/doc/README.u-boot_on_efi

5 U-Boot on EFI
7 This document provides information about U-Boot running on top of EFI, either
18 EFI Application
19 EFI Payload
29 Running U-Boot on EFI is useful in several situations:
31 - You have EFI running on a board but U-Boot does not natively support it
32 fully yet. You can boot into U-Boot from EFI and use that until U-Boot is
35 - You need to use an EFI implementation (e.g. UEFI) because your vendor
40 on EFI and then move to U-Boot on coreboot when ready
42 - You use EFI but want to experiment with a simpler alternative like U-Boot
47 Only x86 is supported at present. If you are using EFI on another architecture
51 U-Boot supports running as an EFI application for 32-bit EFI only. This is
56 or 64-bit EFI. U-Boot is packaged up and loaded in its entirety by EFI. Once
63 First choose a board that has EFI support and obtain an EFI implementation
67 To build U-Boot as an EFI application (32-bit EFI required), enable CONFIG_EFI
68 and CONFIG_EFI_APP. The efi-x86_app config (efi-x86_app_defconfig) is set up
71    make efi-x86_app_defconfig
74 To build U-Boot as an EFI payload (32-bit or 64-bit EFI can be used), enable
76 CONFIG_EFI_STUB_64BIT. The efi-x86_payload configs (efi-x86_payload32_defconfig
77 and efi-x86_payload32_defconfig) are set up for this. Then build U-Boot as
80    make efi-x86_payload32_defconfig (or efi-x86_payload64_defconfig)
85    u-boot-app.efi      - U-Boot EFI application
86    u-boot-payload.efi  - U-Boot EFI payload application
95    mkdir /tmp/efi
96    cp /path/to/u-boot*.efi /tmp/efi
97    qemu-system-x86_64 -bios bios.bin -hda fat:/tmp/efi/
100 type 'fs0:u-boot-payload.efi' to run the payload or 'fs0:u-boot-app.efi' to
101 run the application. 'bios.bin' is the EFI 'BIOS'. Check [2] to obtain a
102 prebuilt EFI BIOS for QEMU or you can build one from source as well.
104 To try it on real hardware, put u-boot-app.efi on a suitable boot medium,
107    fs0:u-boot-payload.efi
109 (or fs0:u-boot-app.efi for the application)
112 that EFI does not support booting a 64-bit application from a 32-bit
113 EFI (or vice versa). Also it will often fail to print an error message if
125 EFI Application
128 efi_main() function is in lib/efi/efi_app.c. It sets up some basic EFI
136 The CONFIG_EFI option controls more general EFI adjustments.
138 The only available driver is the serial driver. This calls back into EFI
141 boot EFI with video output then the 'serial' device will operate on your
145 These are features of EFI, not U-Boot.
147 Very little code is involved in implementing the EFI application feature.
151 arch/x86/cpu. Porting to ARM (which can also use EFI if you are brave
154 Use the 'reset' command to get back to EFI.
156 EFI Payload
160 image (including device tree) into a small EFI stub application responsible
161 for booting it. The stub application is built as a normal EFI application
164 The stub application is implemented in lib/efi/efi_stub.c. The efi_main()
165 function is called by EFI. It is responsible for copying U-Boot from its
166 original location into memory, disabling EFI boot services and starting
172 While the stub application does allocate some memory from EFI this is not
179 The payload can pass information to U-Boot in the form of EFI tables. At
180 present this feature is used to pass the EFI memory map, an inordinately
181 large list of memory regions. You can use the 'efi mem all' command to
185 Although U-Boot can use any memory it likes, EFI marks some memory as used
189 fan speed. U-Boot uses only 'conventional' memory, in EFI terminology. It
195 U-Boot drivers typically don't use interrupts. Since EFI enables interrupts
202 While the EFI application can in principle be built as either 32- or 64-bit,
204 be used with 32-bit EFI.
207 of code is built this way (see the extra- line in lib/efi/Makefile).
231 lib/efi
234 arch/x86/cpu/efi
235 	x86 support code for running as an EFI application and payload
237 board/efi/efi-x86_app/efi.c
238 	x86 board code for running as an EFI application
240 board/efi/efi-x86_payload
241 	generic x86 EFI payload board support code
244 	the 'efi' command