[U-Boot] [PATCH 1/1] doc: integrate UEFI documentation into Sphinx toctree

* [U-Boot] [PATCH 1/1] doc: integrate UEFI documentation into Sphinx toctree
@ 2019-07-26  4:56 Heinrich Schuchardt
  2019-07-26  6:36 ` Bin Meng
  0 siblings, 1 reply; 2+ messages in thread
From: Heinrich Schuchardt @ 2019-07-26  4:56 UTC (permalink / raw)
  To: u-boot

Change the UEFI documentation to Sphinx style and integrate it into the
rest of the Sphinx generated documentation.

Remove the inaccurate TODO list in doc/uefi/uefi.rst.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
---
 MAINTAINERS                |   4 +-
 doc/README.iscsi           | 170 ------------------
 doc/README.u-boot_on_efi   | 252 --------------------------
 doc/README.uefi            | 352 -------------------------------------
 doc/index.rst              |  13 ++
 doc/uefi/index.rst         |  11 ++
 doc/uefi/iscsi.rst         | 180 +++++++++++++++++++
 doc/uefi/u-boot_on_efi.rst | 235 +++++++++++++++++++++++++
 doc/uefi/uefi.rst          | 334 +++++++++++++++++++++++++++++++++++
 9 files changed, 774 insertions(+), 777 deletions(-)
 delete mode 100644 doc/README.iscsi
 delete mode 100644 doc/README.u-boot_on_efi
 delete mode 100644 doc/README.uefi
 create mode 100644 doc/uefi/index.rst
 create mode 100644 doc/uefi/iscsi.rst
 create mode 100644 doc/uefi/u-boot_on_efi.rst
 create mode 100644 doc/uefi/uefi.rst

diff --git a/MAINTAINERS b/MAINTAINERS
index a72ccd0b58..12ad127adc 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -477,9 +477,7 @@ M:	Heinrich Schuchardt <xypron.glpk@gmx.de>
 R:	Alexander Graf <agraf@csgraf.de>
 S:	Maintained
 T:	git https://gitlab.denx.de/u-boot/custodians/u-boot-efi.git
-F:	doc/README.uefi
-F:	doc/README.iscsi
-F:	doc/efi.rst
+F:	doc/uefi/*
 F:	include/capitalization.h
 F:	include/charset.h
 F:	include/cp1250.h
diff --git a/doc/README.iscsi b/doc/README.iscsi
deleted file mode 100644
index 3a12438f90..0000000000
--- a/doc/README.iscsi
+++ /dev/null
@@ -1,170 +0,0 @@
-# iSCSI booting with U-Boot and iPXE
-
-## Motivation
-
-U-Boot has only a reduced set of supported network protocols. The focus for
-network booting has been on UDP based protocols. A TCP stack and HTTP support
-are expected to be integrated in 2018 together with a wget command.
-
-For booting a diskless computer this leaves us with BOOTP or DHCP to get the
-address of a boot script. TFTP or NFS can be used to load the boot script, the
-operating system kernel and the initial file system (initrd).
-
-These protocols are insecure. The client cannot validate the authenticity
-of the contacted servers. And the server cannot verify the identity of the
-client.
-
-Furthermore the services providing the operating system loader or kernel are
-not the ones that the operating system typically will use. Especially in a SAN
-environment this makes updating the operating system a hassle. After installing
-a new kernel version the boot files have to be copied to the TFTP server
-directory.
-
-The HTTPS protocol provides certificate based validation of servers. Sensitive
-data like passwords can be securely transmitted.
-
-The iSCSI protocol is used for connecting storage attached networks. It
-provides mutual authentication using the CHAP protocol. It typically runs on
-a TCP transport.
-
-Thus a better solution than DHCP/TFTP/NFS boot would be to load a boot script
-via HTTPS and to download any other files needed for booting via iSCSI from the
-same target where the operating system is installed.
-
-An alternative to implementing these protocols in U-Boot is to use an existing
-software that can run on top of U-Boot. iPXE[1] is the "swiss army knife" of
-network booting. It supports both HTTPS and iSCSI. It has a scripting engine for
-fine grained control of the boot process and can provide a command shell.
-
-iPXE can be built as an EFI application (named snp.efi) which can be loaded and
-run by U-Boot.
-
-## Boot sequence
-
-U-Boot loads the EFI application iPXE snp.efi using the bootefi command. This
-application has network access via the simple network protocol offered by
-U-Boot.
-
-iPXE executes its internal script. This script may optionally chain load a
-secondary boot script via HTTPS or open a shell.
-
-For the further boot process iPXE connects to the iSCSI server. This includes
-the mutual authentication using the CHAP protocol. After the authentication iPXE
-has access to the iSCSI targets.
-
-For a selected iSCSI target iPXE sets up a handle with the block IO protocol. It
-uses the ConnectController boot service of U-Boot to request U-Boot to connect a
-file system driver. U-Boot reads from the iSCSI drive via the block IO protocol
-offered by iPXE. It creates the partition handles and installs the simple file
-protocol. Now iPXE can call the simple file protocol to load GRUB[2]. U-Boot
-uses the block IO protocol offered by iPXE to fulfill the request.
-
-Once GRUB is started it uses the same block IO protocol to load Linux. Via
-the EFI stub Linux is called as an EFI application::
-
-                  +--------+         +--------+
-                  |        | Runs    |        |
-                  | U-Boot |========>| iPXE   |
-                  | EFI    |         | snp.efi|
-    +--------+    |        | DHCP    |        |
-    |        |<===|********|<========|        |
-    | DHCP   |    |        | Get IP  |        |
-    | Server |    |        | Address |        |
-    |        |===>|********|========>|        |
-    +--------+    |        | Response|        |
-                  |        |         |        |
-                  |        |         |        |
-    +--------+    |        | HTTPS   |        |
-    |        |<===|********|<========|        |
-    | HTTPS  |    |        | Load    |        |
-    | Server |    |        | Script  |        |
-    |        |===>|********|========>|        |
-    +--------+    |        |         |        |
-                  |        |         |        |
-                  |        |         |        |
-    +--------+    |        | iSCSI   |        |
-    |        |<===|********|<========|        |
-    | iSCSI  |    |        | Auth    |        |
-    | Server |===>|********|========>|        |
-    |        |    |        |         |        |
-    |        |    |        | Loads   |        |
-    |        |<===|********|<========|        |       +--------+
-    |        |    |        | GRUB    |        | Runs  |        |
-    |        |===>|********|========>|        |======>| GRUB   |
-    |        |    |        |         |        |       |        |
-    |        |    |        |         |        |       |        |
-    |        |    |        |         |        | Loads |        |
-    |        |<===|********|<========|********|<======|        |      +--------+
-    |        |    |        |         |        | Linux |        | Runs |        |
-    |        |===>|********|========>|********|======>|        |=====>| Linux  |
-    |        |    |        |         |        |       |        |      |        |
-    +--------+    +--------+         +--------+       +--------+      |        |
-                                                                      |        |
-                                                                      |        |
-                                                                      | ~ ~ ~ ~|
-
-## Security
-
-The iSCSI protocol is not encrypted. The traffic could be secured using IPsec
-but neither U-Boot nor iPXE does support this. So we should at least separate
-the iSCSI traffic from all other network traffic. This can be achieved using a
-virtual local area network (VLAN).
-
-## Configuration
-
-### iPXE
-
-For running iPXE on arm64 the bin-arm64-efi/snp.efi build target is needed::
-
-    git clone http://git.ipxe.org/ipxe.git
-    cd ipxe/src
-    make bin-arm64-efi/snp.efi -j6 EMBED=myscript.ipxe
-
-The available commands for the boot script are documented at:
-
-http://ipxe.org/cmd
-
-Credentials are managed as environment variables. These are described here:
-
-http://ipxe.org/cfg
-
-iPXE by default will put the CPU to rest when waiting for input. U-Boot does
-not wake it up due to missing interrupt support. To avoid this behavior create
-file src/config/local/nap.h::
-
-    /* nap.h */
-    #undef NAP_EFIX86
-    #undef NAP_EFIARM
-    #define NAP_NULL
-
-The supported commands in iPXE are controlled by an include, too. Putting the
-following into src/config/local/general.h is sufficient for most use cases::
-
-    /* general.h */
-    #define NSLOOKUP_CMD            /* Name resolution command */
-    #define PING_CMD                /* Ping command */
-    #define NTP_CMD                 /* NTP commands */
-    #define VLAN_CMD                /* VLAN commands */
-    #define IMAGE_EFI               /* EFI image support */
-    #define DOWNLOAD_PROTO_HTTPS    /* Secure Hypertext Transfer Protocol */
-    #define DOWNLOAD_PROTO_FTP      /* File Transfer Protocol */
-    #define DOWNLOAD_PROTO_NFS      /* Network File System Protocol */
-    #define DOWNLOAD_PROTO_FILE     /* Local file system access */
-
-### Open-iSCSI
-
-When the root file system is on an iSCSI drive you should disable pings and set
-the replacement timer to a high value [3]:
-
-    node.conn[0].timeo.noop_out_interval = 0
-    node.conn[0].timeo.noop_out_timeout = 0
-    node.session.timeo.replacement_timeout = 86400
-
-## Links
-
-* [1](https://ipxe.org) https://ipxe.org - iPXE open source boot firmware
-* [2](https://www.gnu.org/software/grub/) https://www.gnu.org/software/grub/ -
-     GNU GRUB (Grand Unified Bootloader)
-* [3](https://github.com/open-iscsi/open-iscsi/blob/master/README)
-     https://github.com/open-iscsi/open-iscsi/blob/master/README -
-     Open-iSCSI README
diff --git a/doc/README.u-boot_on_efi b/doc/README.u-boot_on_efi
deleted file mode 100644
index e12dd4e3e6..0000000000
--- a/doc/README.u-boot_on_efi
+++ /dev/null
@@ -1,252 +0,0 @@
-# SPDX-License-Identifier: GPL-2.0+
-#
-# Copyright (C) 2015 Google, Inc
-
-U-Boot on EFI
-=============
-This document provides information about U-Boot running on top of EFI, either
-as an application or just as a means of getting U-Boot onto a new platform.
-
-
-=========== Table of Contents ===========
-
-Motivation
-Status
-Build Instructions
-Trying it out
-Inner workings
-EFI Application
-EFI Payload
-Tables
-Interrupts
-32/64-bit
-Future work
-Where is the code?
-
-
-Motivation
-----------
-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
-
-
-Status
-------
-Only x86 is supported at present. If you are using EFI on another architecture
-you may want to reconsider. However, much of the code is generic so could be
-ported.
-
-U-Boot supports running as an EFI application for 32-bit EFI only. This is
-not very useful since only a serial port is provided. You can look around at
-memory and type 'help' but that is about it.
-
-More usefully, U-Boot supports building itself as a payload for either 32-bit
-or 64-bit EFI. U-Boot is packaged up and loaded in its entirety by EFI. Once
-started, U-Boot changes to 32-bit mode (currently) and takes over the
-machine. You can use devices, boot a kernel, etc.
-
-
-Build Instructions
-------------------
-First choose a board that has EFI support and obtain an EFI implementation
-for that board. It will be either 32-bit or 64-bit. Alternatively, you can
-opt for using QEMU [1] and the OVMF [2], as detailed below.
-
-To build U-Boot as an EFI application (32-bit EFI required), enable CONFIG_EFI
-and CONFIG_EFI_APP. The efi-x86_app config (efi-x86_app_defconfig) is set up
-for this. Just build U-Boot as normal, e.g.
-
-   make efi-x86_app_defconfig
-   make
-
-To build U-Boot as an EFI payload (32-bit or 64-bit EFI can be used), enable
-CONFIG_EFI, CONFIG_EFI_STUB, and select either CONFIG_EFI_STUB_32BIT or
-CONFIG_EFI_STUB_64BIT. The efi-x86_payload configs (efi-x86_payload32_defconfig
-and efi-x86_payload32_defconfig) are set up for this. Then build U-Boot as
-normal, e.g.
-
-   make efi-x86_payload32_defconfig (or efi-x86_payload64_defconfig)
-   make
-
-You will end up with one of these files depending on what you build for:
-
-   u-boot-app.efi      - U-Boot EFI application
-   u-boot-payload.efi  - U-Boot EFI payload application
-
-
-Trying it out
--------------
-QEMU is an emulator and it can emulate an x86 machine. Please make sure your
-QEMU version is 2.3.0 or above to test this. You can run the payload with
-something like this:
-
-   mkdir /tmp/efi
-   cp /path/to/u-boot*.efi /tmp/efi
-   qemu-system-x86_64 -bios bios.bin -hda fat:/tmp/efi/
-
-Add -nographic if you want to use the terminal for output. Once it starts
-type 'fs0:u-boot-payload.efi' to run the payload or 'fs0:u-boot-app.efi' to
-run the application. 'bios.bin' is the EFI 'BIOS'. Check [2] to obtain a
-prebuilt EFI BIOS for QEMU or you can build one from source as well.
-
-To try it on real hardware, put u-boot-app.efi on a suitable boot medium,
-such as a USB stick. Then you can type something like this to start it:
-
-   fs0:u-boot-payload.efi
-
-(or fs0:u-boot-app.efi for the application)
-
-This will start the payload, copy U-Boot into RAM and start U-Boot. Note
-that EFI does not support booting a 64-bit application from a 32-bit
-EFI (or vice versa). Also it will often fail to print an error message if
-you get this wrong.
-
-
-Inner workings
-==============
-Here follow a few implementation notes for those who want to fiddle with
-this and perhaps contribute patches.
-
-The application and payload approaches sound similar but are in fact
-implemented completely differently.
-
-EFI Application
----------------
-For the application the whole of U-Boot is built as a shared library. The
-efi_main() function is in lib/efi/efi_app.c. It sets up some basic EFI
-functions with efi_init(), sets up U-Boot global_data, allocates memory for
-U-Boot's malloc(), etc. and enters the normal init sequence (board_init_f()
-and board_init_r()).
-
-Since U-Boot limits its memory access to the allocated regions very little
-special code is needed. The CONFIG_EFI_APP option controls a few things
-that need to change so 'git grep CONFIG_EFI_APP' may be instructive.
-The CONFIG_EFI option controls more general EFI adjustments.
-
-The only available driver is the serial driver. This calls back into EFI
-'boot services' to send and receive characters. Although it is implemented
-as a serial driver the console device is not necessarilly serial. If you
-boot EFI with video output then the 'serial' device will operate on your
-target devices's display instead and the device's USB keyboard will also
-work if connected. If you have both serial and video output, then both
-consoles will be active. Even though U-Boot does the same thing normally,
-These are features of EFI, not U-Boot.
-
-Very little code is involved in implementing the EFI application feature.
-U-Boot is highly portable. Most of the difficulty is in modifying the
-Makefile settings to pass the right build flags. In particular there is very
-little x86-specific code involved - you can find most of it in
-arch/x86/cpu. Porting to ARM (which can also use EFI if you are brave
-enough) should be straightforward.
-
-Use the 'reset' command to get back to EFI.
-
-EFI Payload
------------
-The payload approach is a different kettle of fish. It works by building
-U-Boot exactly as normal for your target board, then adding the entire
-image (including device tree) into a small EFI stub application responsible
-for booting it. The stub application is built as a normal EFI application
-except that it has a lot of data attached to it.
-
-The stub application is implemented in lib/efi/efi_stub.c. The efi_main()
-function is called by EFI. It is responsible for copying U-Boot from its
-original location into memory, disabling EFI boot services and starting
-U-Boot. U-Boot then starts as normal, relocates, starts all drivers, etc.
-
-The stub application is architecture-dependent. At present it has some
-x86-specific code and a comment at the top of efi_stub.c describes this.
-
-While the stub application does allocate some memory from EFI this is not
-used by U-Boot (the payload). In fact when U-Boot starts it has all of the
-memory available to it and can operate as it pleases (but see the next
-section).
-
-Tables
-------
-The payload can pass information to U-Boot in the form of EFI tables. At
-present this feature is used to pass the EFI memory map, an inordinately
-large list of memory regions. You can use the 'efi mem all' command to
-display this list. U-Boot uses the list to work out where to relocate
-itself.
-
-Although U-Boot can use any memory it likes, EFI marks some memory as used
-by 'run-time services', code that hangs around while U-Boot is running and
-is even present when Linux is running. This is common on x86 and provides
-a way for Linux to call back into the firmware to control things like CPU
-fan speed. U-Boot uses only 'conventional' memory, in EFI terminology. It
-will relocate itself to the top of the largest block of memory it can find
-below 4GB.
-
-Interrupts
-----------
-U-Boot drivers typically don't use interrupts. Since EFI enables interrupts
-it is possible that an interrupt will fire that U-Boot cannot handle. This
-seems to cause problems. For this reason the U-Boot payload runs with
-interrupts disabled at present.
-
-32/64-bit
----------
-While the EFI application can in principle be built as either 32- or 64-bit,
-only 32-bit is currently supported. This means that the application can only
-be used with 32-bit EFI.
-
-The payload stub can be build as either 32- or 64-bits. Only a small amount
-of code is built this way (see the extra- line in lib/efi/Makefile).
-Everything else is built as a normal U-Boot, so is always 32-bit on x86 at
-present.
-
-Future work
------------
-This work could be extended in a number of ways:
-
-- Add ARM support
-
-- Add 64-bit application support
-
-- Figure out how to solve the interrupt problem
-
-- Add more drivers to the application side (e.g. video, block devices, USB,
-environment access). This would mostly be an academic exercise as a strong
-use case is not readily apparent, but it might be fun.
-
-- Avoid turning off boot services in the stub. Instead allow U-Boot to make
-use of boot services in case it wants to. It is unclear what it might want
-though.
-
-Where is the code?
-------------------
-lib/efi
-	payload stub, application, support code. Mostly arch-neutral
-
-arch/x86/cpu/efi
-	x86 support code for running as an EFI application and payload
-
-board/efi/efi-x86_app/efi.c
-	x86 board code for running as an EFI application
-
-board/efi/efi-x86_payload
-	generic x86 EFI payload board support code
-
-common/cmd_efi.c
-	the 'efi' command
-
---
-Ben Stoltz, Simon Glass
-Google, Inc
-July 2015
-
-[1] http://www.qemu.org
-[2] http://www.tianocore.org/ovmf/
diff --git a/doc/README.uefi b/doc/README.uefi
deleted file mode 100644
index 1d1039a6ae..0000000000
--- a/doc/README.uefi
+++ /dev/null
@@ -1,352 +0,0 @@
-<!--
-SPDX-License-Identifier: GPL-2.0+
-
-Copyright (c) 2018 Heinrich Schuchardt
--->
-
-# UEFI on U-Boot
-
-The Unified Extensible Firmware Interface Specification (UEFI) [1] has become
-the default for booting on AArch64 and x86 systems. It provides a stable API for
-the interaction of drivers and applications with the firmware. The API comprises
-access to block storage, network, and console to name a few. The Linux kernel
-and boot loaders like GRUB or the FreeBSD loader can be executed.
-
-## Development target
-
-The implementation of UEFI in U-Boot strives to reach the requirements described
-in the "Embedded Base Boot Requirements (EBBR) Specification - Release v1.0"
-[4]. The "Server Base Boot Requirements System Software on ARM Platforms" [5]
-describes a superset of the EBBR specification and may be used as further
-reference.
-
-A full blown UEFI implementation would contradict the U-Boot design principle
-"keep it small".
-
-## Building for UEFI
-
-The UEFI standard supports only little-endian systems. The UEFI support can be
-activated for ARM and x86 by specifying
-
-    CONFIG_CMD_BOOTEFI=y
-    CONFIG_EFI_LOADER=y
-
-in the .config file.
-
-Support for attaching virtual block devices, e.g. iSCSI drives connected by the
-loaded UEFI application [3], requires
-
-    CONFIG_BLK=y
-    CONFIG_PARTITIONS=y
-
-### Executing a UEFI binary
-
-The bootefi command is used to start UEFI applications or to install UEFI
-drivers. It takes two parameters
-
-    bootefi <image address> [fdt address]
-
-* image address - the memory address of the UEFI binary
-* fdt address - the memory address of the flattened device tree
-
-Below you find the output of an example session starting GRUB.
-
-    => load mmc 0:2 ${fdt_addr_r} boot/dtb
-    29830 bytes read in 14 ms (2 MiB/s)
-    => load mmc 0:1 ${kernel_addr_r} efi/debian/grubaa64.efi
-    reading efi/debian/grubaa64.efi
-    120832 bytes read in 7 ms (16.5 MiB/s)
-    => bootefi ${kernel_addr_r} ${fdt_addr_r}
-
-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.
-
-### 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
-
-    bootefi bootmgr [fdt address]
-
-As of U-Boot v2018.03 UEFI variables are not persisted and cannot be set at
-runtime.
-
-### Executing the built in hello world application
-
-A hello world UEFI application can be built with
-
-    CONFIG_CMD_BOOTEFI_HELLO_COMPILE=y
-
-It can be embedded into the U-Boot binary with
-
-    CONFIG_CMD_BOOTEFI_HELLO=y
-
-The bootefi command is used to start the embedded hello world application.
-
-    bootefi hello [fdt address]
-
-Below you find the output of an example session.
-
-    => bootefi hello ${fdtcontroladdr}
-    ## Starting EFI application at 01000000 ...
-    WARNING: using memory device/image path, this may confuse some payloads!
-    Hello, world!
-    Running on UEFI 2.7
-    Have SMBIOS table
-    Have device tree
-    Load options: root=/dev/sdb3 init=/sbin/init rootwait ro
-    ## Application terminated, r = 0
-
-The environment variable fdtcontroladdr points to U-Boot's internal device tree
-(if available).
-
-### Executing the built-in self-test
-
-An UEFI self-test suite can be embedded in U-Boot by building with
-
-    CONFIG_CMD_BOOTEFI_SELFTEST=y
-
-For testing the UEFI implementation the bootefi command can be used to start the
-self-test.
-
-    bootefi selftest [fdt address]
-
-The environment variable 'efi_selftest' can be used to select a single test. If
-it is not provided all tests are executed except those marked as 'on request'.
-If the environment variable is set to 'list' a list of all tests is shown.
-
-Below you can find the output of an example session.
-
-    => setenv efi_selftest simple network protocol
-    => bootefi selftest
-    Testing EFI API implementation
-    Selected test: 'simple network protocol'
-    Setting up 'simple network protocol'
-    Setting up 'simple network protocol' succeeded
-    Executing 'simple network protocol'
-    DHCP Discover
-    DHCP reply received from 192.168.76.2 (52:55:c0:a8:4c:02)
-      as broadcast message.
-    Executing 'simple network protocol' succeeded
-    Tearing down 'simple network protocol'
-    Tearing down 'simple network protocol' succeeded
-    Boot services terminated
-    Summary: 0 failures
-    Preparing for reset. Press any key.
-
-## The UEFI life cycle
-
-After the U-Boot platform has been initialized the UEFI API provides two kinds
-of services
-
-* boot services and
-* runtime services.
-
-The API can be extended by loading UEFI drivers which come in two variants
-
-* boot drivers and
-* runtime drivers.
-
-UEFI drivers are installed with U-Boot's bootefi command. With the same command
-UEFI applications can be executed.
-
-Loaded images of UEFI drivers stay in memory after returning to U-Boot while
-loaded images of applications are removed from memory.
-
-An UEFI application (e.g. an operating system) that wants to take full control
-of the system calls ExitBootServices. After a UEFI application calls
-ExitBootServices
-
-* boot services are not available anymore
-* timer events are stopped
-* the memory used by U-Boot except for runtime services is released
-* the memory used by boot time drivers is released
-
-So this is a point of no return. Afterwards the UEFI application can only return
-to U-Boot by rebooting.
-
-## The UEFI object model
-
-UEFI offers a flexible and expandable object model. The objects in the UEFI API
-are devices, drivers, and loaded images. These objects are referenced by
-handles.
-
-The interfaces implemented by the objects are referred to as protocols. These
-are identified by GUIDs. They can be installed and uninstalled by calling the
-appropriate boot services.
-
-Handles are created by the InstallProtocolInterface or the
-InstallMultipleProtocolinterfaces service if NULL is passed as handle.
-
-Handles are deleted when the last protocol has been removed with the
-UninstallProtocolInterface or the UninstallMultipleProtocolInterfaces service.
-
-Devices offer the EFI_DEVICE_PATH_PROTOCOL. A device path is the concatenation
-of device nodes. By their device paths all devices of a system are arranged in a
-tree.
-
-Drivers offer the EFI_DRIVER_BINDING_PROTOCOL. This protocol is used to connect
-a driver to devices (which are referenced as controllers in this context).
-
-Loaded images offer the EFI_LOADED_IMAGE_PROTOCOL. This protocol provides meta
-information about the image and a pointer to the unload callback function.
-
-## The UEFI events
-
-In the UEFI terminology an event is a data object referencing a notification
-function which is queued for calling when the event is signaled. The following
-types of events exist:
-
-* periodic and single shot timer events
-* exit boot services events, triggered by calling the ExitBootServices() service
-* virtual address change events
-* memory map change events
-* read to boot events
-* reset system events
-* system table events
-* events that are only triggered programmatically
-
-Events can be created with the CreateEvent service and deleted with CloseEvent
-service.
-
-Events can be assigned to an event group. If any of the events in a group is
-signaled, all other events in the group are also set to the signaled state.
-
-## The UEFI driver model
-
-A driver is specific for a single protocol installed on a device. To install a
-driver on a device the ConnectController service is called. In this context
-controller refers to the device for which the driver is installed.
-
-The relevant drivers are identified using the EFI_DRIVER_BINDING_PROTOCOL. This
-protocol has has three functions:
-
-* supported - determines if the driver is compatible with the device
-* start - installs the driver by opening the relevant protocol with
-  attribute EFI_OPEN_PROTOCOL_BY_DRIVER
-* stop - uninstalls the driver
-
-The driver may create child controllers (child devices). E.g. a driver for block
-IO devices will create the device handles for the partitions. The child
-controllers  will open the supported protocol with the attribute
-EFI_OPEN_PROTOCOL_BY_CHILD_CONTROLLER.
-
-A driver can be detached from a device using the DisconnectController service.
-
-## U-Boot devices mapped as UEFI devices
-
-Some of the U-Boot devices are mapped as UEFI devices
-
-* block IO devices
-* console
-* graphical output
-* network adapter
-
-As of U-Boot 2018.03 the logic for doing this is hard coded.
-
-The development target is to integrate the setup of these UEFI devices with the
-U-Boot driver model. So when a U-Boot device is discovered a handle should be
-created and the device path protocol and the relevant IO protocol should be
-installed. The UEFI driver then would be attached by calling ConnectController.
-When a U-Boot device is removed DisconnectController should be called.
-
-## UEFI devices mapped as U-Boot devices
-
-UEFI drivers binaries and applications may create new (virtual) devices, install
-a protocol and call the ConnectController service. Now the matching UEFI driver
-is determined by iterating over the implementations of the
-EFI_DRIVER_BINDING_PROTOCOL.
-
-It is the task of the UEFI driver to create a corresponding U-Boot device and to
-proxy calls for this U-Boot device to the controller.
-
-In U-Boot 2018.03 this has only been implemented for block IO devices.
-
-### UEFI uclass
-
-An UEFI uclass driver (lib/efi_driver/efi_uclass.c) has been created that
-takes care of initializing the UEFI drivers and providing the
-EFI_DRIVER_BINDING_PROTOCOL implementation for the UEFI drivers.
-
-A linker created list is used to keep track of the UEFI drivers. To create an
-entry in the list the UEFI driver uses the U_BOOT_DRIVER macro specifying
-UCLASS_EFI as the ID of its uclass, e.g.
-
-    /* Identify as UEFI driver */
-    U_BOOT_DRIVER(efi_block) = {
-    	.name  = "EFI block driver",
-    	.id    = UCLASS_EFI,
-    	.ops   = &driver_ops,
-    };
-
-The available operations are defined via the structure struct efi_driver_ops.
-
-    struct efi_driver_ops {
-        const efi_guid_t *protocol;
-        const efi_guid_t *child_protocol;
-        int (*bind)(efi_handle_t handle, void *interface);
-    };
-
-When the supported() function of the EFI_DRIVER_BINDING_PROTOCOL is called the
-uclass checks if the protocol GUID matches the protocol GUID of the UEFI driver.
-In the start() function the bind() function of the UEFI driver is called after
-checking the GUID.
-The stop() function of the EFI_DRIVER_BINDING_PROTOCOL disconnects the child
-controllers created by the UEFI driver and the UEFI driver. (In U-Boot v2013.03
-this is not yet completely implemented.)
-
-### UEFI block IO driver
-
-The UEFI block IO driver supports devices exposing the EFI_BLOCK_IO_PROTOCOL.
-
-When connected it creates a new U-Boot block IO device with interface type
-IF_TYPE_EFI, adds child controllers mapping the partitions, and installs the
-EFI_SIMPLE_FILE_SYSTEM_PROTOCOL on these. This can be used together with the
-software iPXE to boot from iSCSI network drives [3].
-
-This driver is only available if U-Boot is configured with
-
-    CONFIG_BLK=y
-    CONFIG_PARTITIONS=y
-
-## TODOs as of U-Boot 2019.04
-
-* unimplemented or incompletely implemented boot services
-  * Exit - call unload function, unload applications only
-  * ProtocolRegisterNotify
-  * UnloadImage
-
-* unimplemented or incompletely implemented runtime services
-  * SetVariable() ignores attribute EFI_VARIABLE_APPEND_WRITE
-  * QueryVariableInfo is not implemented
-
-* unimplemented events
-  * EVT_RUNTIME
-  * EVT_SIGNAL_VIRTUAL_ADDRESS_CHANGE
-
-* data model
-  * manage configuration tables in a linked list
-
-* UEFI drivers
-  * support DisconnectController for UEFI block devices.
-
-* support for CONFIG_EFI_LOADER in the sandbox (CONFIG_SANDBOX=y)
-
-* UEFI variables
-  * persistence
-  * runtime support
-
-* incompletely implemented protocols
-  * support version 0x00020000 of the EFI file protocol
-
-## Links
-
-* [1](http://uefi.org/specifications)
-  http://uefi.org/specifications - UEFI specifications
-* [2](./driver-model/README.txt) doc/driver-model/README.txt - Driver model
-* [3](./README.iscsi) doc/README.iscsi - iSCSI booting with U-Boot and iPXE
-* [4](https://github.com/ARM-software/ebbr/releases/download/v1.0/ebbr-v1.0.pdf)
-  Embedded Base Boot Requirements (EBBR) Specification - Release v1.0
-* [5](https://developer.arm.com/docs/den0044/latest/server-base-boot-requirements-system-software-on-arm-platforms-version-11)
-  Server Base Boot Requirements System Software on ARM Platforms - Version 1.1
diff --git a/doc/index.rst b/doc/index.rst
index 9ae2e167bc..458f0d2d0e 100644
--- a/doc/index.rst
+++ b/doc/index.rst
@@ -15,8 +15,21 @@ if you want to help out.
 .. toctree::
    :maxdepth: 2

+Unified Extensible Firmware (UEFI)
+----------------------------------
+
+U-Boot provides an implementation of the UEFI API allowing to run UEFI
+compliant software like Linux, GRUB, and iPXE. Furthermore U-Boot itself
+can be run an UEFI payload.
+
+.. toctree::
+   :maxdepth: 2
+
+   uefi/index
+
 Driver-Model documentation
 --------------------------
+
 The following holds information on the U-Boot device driver framework:
 driver-model, including the design details of itself and several driver
 subsystems.
diff --git a/doc/uefi/index.rst b/doc/uefi/index.rst
new file mode 100644
index 0000000000..b790a91f17
--- /dev/null
+++ b/doc/uefi/index.rst
@@ -0,0 +1,11 @@
+.. SPDX-License-Identifier: GPL-2.0+
+
+Unified Extensible Firmware (UEFI)
+==================================
+
+.. toctree::
+   :maxdepth: 2
+
+   uefi.rst
+   u-boot_on_efi.rst
+   iscsi.rst
diff --git a/doc/uefi/iscsi.rst b/doc/uefi/iscsi.rst
new file mode 100644
index 0000000000..aa844a7cc3
--- /dev/null
+++ b/doc/uefi/iscsi.rst
@@ -0,0 +1,180 @@
+.. SPDX-License-Identifier: GPL-2.0+
+.. Copyright (c) 2018 Heinrich Schuchardt
+
+iSCSI booting with U-Boot and iPXE
+==================================
+
+Motivation
+----------
+
+U-Boot has only a reduced set of supported network protocols. The focus for
+network booting has been on UDP based protocols. A TCP stack and HTTP support
+are expected to be integrated in 2018 together with a wget command.
+
+For booting a diskless computer this leaves us with BOOTP or DHCP to get the
+address of a boot script. TFTP or NFS can be used to load the boot script, the
+operating system kernel and the initial file system (initrd).
+
+These protocols are insecure. The client cannot validate the authenticity
+of the contacted servers. And the server cannot verify the identity of the
+client.
+
+Furthermore the services providing the operating system loader or kernel are
+not the ones that the operating system typically will use. Especially in a SAN
+environment this makes updating the operating system a hassle. After installing
+a new kernel version the boot files have to be copied to the TFTP server
+directory.
+
+The HTTPS protocol provides certificate based validation of servers. Sensitive
+data like passwords can be securely transmitted.
+
+The iSCSI protocol is used for connecting storage attached networks. It
+provides mutual authentication using the CHAP protocol. It typically runs on
+a TCP transport.
+
+Thus a better solution than DHCP/TFTP/NFS boot would be to load a boot script
+via HTTPS and to download any other files needed for booting via iSCSI from the
+same target where the operating system is installed.
+
+An alternative to implementing these protocols in U-Boot is to use an existing
+software that can run on top of U-Boot. iPXE[1] is the "swiss army knife" of
+network booting. It supports both HTTPS and iSCSI. It has a scripting engine for
+fine grained control of the boot process and can provide a command shell.
+
+iPXE can be built as an EFI application (named snp.efi) which can be loaded and
+run by U-Boot.
+
+Boot sequence
+-------------
+
+U-Boot loads the EFI application iPXE snp.efi using the bootefi command. This
+application has network access via the simple network protocol offered by
+U-Boot.
+
+iPXE executes its internal script. This script may optionally chain load a
+secondary boot script via HTTPS or open a shell.
+
+For the further boot process iPXE connects to the iSCSI server. This includes
+the mutual authentication using the CHAP protocol. After the authentication iPXE
+has access to the iSCSI targets.
+
+For a selected iSCSI target iPXE sets up a handle with the block IO protocol. It
+uses the ConnectController boot service of U-Boot to request U-Boot to connect a
+file system driver. U-Boot reads from the iSCSI drive via the block IO protocol
+offered by iPXE. It creates the partition handles and installs the simple file
+protocol. Now iPXE can call the simple file protocol to load GRUB[2]. U-Boot
+uses the block IO protocol offered by iPXE to fulfill the request.
+
+Once GRUB is started it uses the same block IO protocol to load Linux. Via
+the EFI stub Linux is called as an EFI application::
+
+                  +--------+         +--------+
+                  |        | Runs    |        |
+                  | U-Boot |========>| iPXE   |
+                  | EFI    |         | snp.efi|
+    +--------+    |        | DHCP    |        |
+    |        |<===|********|<========|        |
+    | DHCP   |    |        | Get IP  |        |
+    | Server |    |        | Address |        |
+    |        |===>|********|========>|        |
+    +--------+    |        | Response|        |
+                  |        |         |        |
+                  |        |         |        |
+    +--------+    |        | HTTPS   |        |
+    |        |<===|********|<========|        |
+    | HTTPS  |    |        | Load    |        |
+    | Server |    |        | Script  |        |
+    |        |===>|********|========>|        |
+    +--------+    |        |         |        |
+                  |        |         |        |
+                  |        |         |        |
+    +--------+    |        | iSCSI   |        |
+    |        |<===|********|<========|        |
+    | iSCSI  |    |        | Auth    |        |
+    | Server |===>|********|========>|        |
+    |        |    |        |         |        |
+    |        |    |        | Loads   |        |
+    |        |<===|********|<========|        |       +--------+
+    |        |    |        | GRUB    |        | Runs  |        |
+    |        |===>|********|========>|        |======>| GRUB   |
+    |        |    |        |         |        |       |        |
+    |        |    |        |         |        |       |        |
+    |        |    |        |         |        | Loads |        |
+    |        |<===|********|<========|********|<======|        |      +--------+
+    |        |    |        |         |        | Linux |        | Runs |        |
+    |        |===>|********|========>|********|======>|        |=====>| Linux  |
+    |        |    |        |         |        |       |        |      |        |
+    +--------+    +--------+         +--------+       +--------+      |        |
+                                                                      |        |
+                                                                      |        |
+                                                                      | ~ ~ ~ ~|
+
+Security
+--------
+
+The iSCSI protocol is not encrypted. The traffic could be secured using IPsec
+but neither U-Boot nor iPXE does support this. So we should at least separate
+the iSCSI traffic from all other network traffic. This can be achieved using a
+virtual local area network (VLAN).
+
+Configuration
+-------------
+
+iPXE
+~~~~
+
+For running iPXE on arm64 the bin-arm64-efi/snp.efi build target is needed::
+
+    git clone http://git.ipxe.org/ipxe.git
+    cd ipxe/src
+    make bin-arm64-efi/snp.efi -j6 EMBED=myscript.ipxe
+
+The available commands for the boot script are documented at:
+
+http://ipxe.org/cmd
+
+Credentials are managed as environment variables. These are described here:
+
+http://ipxe.org/cfg
+
+iPXE by default will put the CPU to rest when waiting for input. U-Boot does
+not wake it up due to missing interrupt support. To avoid this behavior create
+file src/config/local/nap.h::
+
+    /* nap.h */
+    #undef NAP_EFIX86
+    #undef NAP_EFIARM
+    #define NAP_NULL
+
+The supported commands in iPXE are controlled by an include, too. Putting the
+following into src/config/local/general.h is sufficient for most use cases::
+
+    /* general.h */
+    #define NSLOOKUP_CMD            /* Name resolution command */
+    #define PING_CMD                /* Ping command */
+    #define NTP_CMD                 /* NTP commands */
+    #define VLAN_CMD                /* VLAN commands */
+    #define IMAGE_EFI               /* EFI image support */
+    #define DOWNLOAD_PROTO_HTTPS    /* Secure Hypertext Transfer Protocol */
+    #define DOWNLOAD_PROTO_FTP      /* File Transfer Protocol */
+    #define DOWNLOAD_PROTO_NFS      /* Network File System Protocol */
+    #define DOWNLOAD_PROTO_FILE     /* Local file system access */
+
+Open-iSCSI
+~~~~~~~~~~
+
+When the root file system is on an iSCSI drive you should disable pings and set
+the replacement timer to a high value [3]:
+
+    node.conn[0].timeo.noop_out_interval = 0
+    node.conn[0].timeo.noop_out_timeout = 0
+    node.session.timeo.replacement_timeout = 86400
+
+Links
+-----
+
+* [1] https://ipxe.org - iPXE open source boot firmware
+* [2] https://www.gnu.org/software/grub/ -
+  GNU GRUB (Grand Unified Bootloader)
+* [3] https://github.com/open-iscsi/open-iscsi/blob/master/README -
+  Open-iSCSI README
diff --git a/doc/uefi/u-boot_on_efi.rst b/doc/uefi/u-boot_on_efi.rst
new file mode 100644
index 0000000000..139173bc7a
--- /dev/null
+++ b/doc/uefi/u-boot_on_efi.rst
@@ -0,0 +1,235 @@
+.. SPDX-License-Identifier: GPL-2.0+
+.. Copyright (C) 2015 Google, Inc
+
+U-Boot on EFI
+=============
+This document provides information about U-Boot running on top of EFI, either
+as an application or just as a means of getting U-Boot onto a new platform.
+
+
+Motivation
+----------
+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
+
+
+Status
+------
+Only x86 is supported at present. If you are using EFI on another architecture
+you may want to reconsider. However, much of the code is generic so could be
+ported.
+
+U-Boot supports running as an EFI application for 32-bit EFI only. This is
+not very useful since only a serial port is provided. You can look around at
+memory and type 'help' but that is about it.
+
+More usefully, U-Boot supports building itself as a payload for either 32-bit
+or 64-bit EFI. U-Boot is packaged up and loaded in its entirety by EFI. Once
+started, U-Boot changes to 32-bit mode (currently) and takes over the
+machine. You can use devices, boot a kernel, etc.
+
+
+Build Instructions
+------------------
+First choose a board that has EFI support and obtain an EFI implementation
+for that board. It will be either 32-bit or 64-bit. Alternatively, you can
+opt for using QEMU [1] and the OVMF [2], as detailed below.
+
+To build U-Boot as an EFI application (32-bit EFI required), enable CONFIG_EFI
+and CONFIG_EFI_APP. The efi-x86_app config (efi-x86_app_defconfig) is set up
+for this. Just build U-Boot as normal, e.g.
+
+   make efi-x86_app_defconfig
+   make
+
+To build U-Boot as an EFI payload (32-bit or 64-bit EFI can be used), enable
+CONFIG_EFI, CONFIG_EFI_STUB, and select either CONFIG_EFI_STUB_32BIT or
+CONFIG_EFI_STUB_64BIT. The efi-x86_payload configs (efi-x86_payload32_defconfig
+and efi-x86_payload32_defconfig) are set up for this. Then build U-Boot as
+normal, e.g.
+
+   make efi-x86_payload32_defconfig (or efi-x86_payload64_defconfig)
+   make
+
+You will end up with one of these files depending on what you build for:
+
+   u-boot-app.efi      - U-Boot EFI application
+   u-boot-payload.efi  - U-Boot EFI payload application
+
+
+Trying it out
+-------------
+QEMU is an emulator and it can emulate an x86 machine. Please make sure your
+QEMU version is 2.3.0 or above to test this. You can run the payload with
+something like this:
+
+   mkdir /tmp/efi
+   cp /path/to/u-boot*.efi /tmp/efi
+   qemu-system-x86_64 -bios bios.bin -hda fat:/tmp/efi/
+
+Add -nographic if you want to use the terminal for output. Once it starts
+type 'fs0:u-boot-payload.efi' to run the payload or 'fs0:u-boot-app.efi' to
+run the application. 'bios.bin' is the EFI 'BIOS'. Check [2] to obtain a
+prebuilt EFI BIOS for QEMU or you can build one from source as well.
+
+To try it on real hardware, put u-boot-app.efi on a suitable boot medium,
+such as a USB stick. Then you can type something like this to start it:
+
+   fs0:u-boot-payload.efi
+
+(or fs0:u-boot-app.efi for the application)
+
+This will start the payload, copy U-Boot into RAM and start U-Boot. Note
+that EFI does not support booting a 64-bit application from a 32-bit
+EFI (or vice versa). Also it will often fail to print an error message if
+you get this wrong.
+
+
+Inner workings
+--------------
+Here follow a few implementation notes for those who want to fiddle with
+this and perhaps contribute patches.
+
+The application and payload approaches sound similar but are in fact
+implemented completely differently.
+
+EFI Application
+~~~~~~~~~~~~~~~
+For the application the whole of U-Boot is built as a shared library. The
+efi_main() function is in lib/efi/efi_app.c. It sets up some basic EFI
+functions with efi_init(), sets up U-Boot global_data, allocates memory for
+U-Boot's malloc(), etc. and enters the normal init sequence (board_init_f()
+and board_init_r()).
+
+Since U-Boot limits its memory access to the allocated regions very little
+special code is needed. The CONFIG_EFI_APP option controls a few things
+that need to change so 'git grep CONFIG_EFI_APP' may be instructive.
+The CONFIG_EFI option controls more general EFI adjustments.
+
+The only available driver is the serial driver. This calls back into EFI
+'boot services' to send and receive characters. Although it is implemented
+as a serial driver the console device is not necessarilly serial. If you
+boot EFI with video output then the 'serial' device will operate on your
+target devices's display instead and the device's USB keyboard will also
+work if connected. If you have both serial and video output, then both
+consoles will be active. Even though U-Boot does the same thing normally,
+These are features of EFI, not U-Boot.
+
+Very little code is involved in implementing the EFI application feature.
+U-Boot is highly portable. Most of the difficulty is in modifying the
+Makefile settings to pass the right build flags. In particular there is very
+little x86-specific code involved - you can find most of it in
+arch/x86/cpu. Porting to ARM (which can also use EFI if you are brave
+enough) should be straightforward.
+
+Use the 'reset' command to get back to EFI.
+
+EFI Payload
+~~~~~~~~~~~
+The payload approach is a different kettle of fish. It works by building
+U-Boot exactly as normal for your target board, then adding the entire
+image (including device tree) into a small EFI stub application responsible
+for booting it. The stub application is built as a normal EFI application
+except that it has a lot of data attached to it.
+
+The stub application is implemented in lib/efi/efi_stub.c. The efi_main()
+function is called by EFI. It is responsible for copying U-Boot from its
+original location into memory, disabling EFI boot services and starting
+U-Boot. U-Boot then starts as normal, relocates, starts all drivers, etc.
+
+The stub application is architecture-dependent. At present it has some
+x86-specific code and a comment at the top of efi_stub.c describes this.
+
+While the stub application does allocate some memory from EFI this is not
+used by U-Boot (the payload). In fact when U-Boot starts it has all of the
+memory available to it and can operate as it pleases (but see the next
+section).
+
+Tables
+~~~~~~
+The payload can pass information to U-Boot in the form of EFI tables. At
+present this feature is used to pass the EFI memory map, an inordinately
+large list of memory regions. You can use the 'efi mem all' command to
+display this list. U-Boot uses the list to work out where to relocate
+itself.
+
+Although U-Boot can use any memory it likes, EFI marks some memory as used
+by 'run-time services', code that hangs around while U-Boot is running and
+is even present when Linux is running. This is common on x86 and provides
+a way for Linux to call back into the firmware to control things like CPU
+fan speed. U-Boot uses only 'conventional' memory, in EFI terminology. It
+will relocate itself to the top of the largest block of memory it can find
+below 4GB.
+
+Interrupts
+~~~~~~~~~~
+U-Boot drivers typically don't use interrupts. Since EFI enables interrupts
+it is possible that an interrupt will fire that U-Boot cannot handle. This
+seems to cause problems. For this reason the U-Boot payload runs with
+interrupts disabled at present.
+
+32/64-bit
+~~~~~~~~~
+While the EFI application can in principle be built as either 32- or 64-bit,
+only 32-bit is currently supported. This means that the application can only
+be used with 32-bit EFI.
+
+The payload stub can be build as either 32- or 64-bits. Only a small amount
+of code is built this way (see the extra- line in lib/efi/Makefile).
+Everything else is built as a normal U-Boot, so is always 32-bit on x86 at
+present.
+
+Future work
+-----------
+This work could be extended in a number of ways:
+
+- Add ARM support
+
+- Add 64-bit application support
+
+- Figure out how to solve the interrupt problem
+
+- Add more drivers to the application side (e.g. video, block devices, USB,
+  environment access). This would mostly be an academic exercise as a strong
+  use case is not readily apparent, but it might be fun.
+
+- Avoid turning off boot services in the stub. Instead allow U-Boot to make
+  use of boot services in case it wants to. It is unclear what it might want
+  though.
+
+Where is the code?
+------------------
+lib/efi
+	payload stub, application, support code. Mostly arch-neutral
+
+arch/x86/cpu/efi
+	x86 support code for running as an EFI application and payload
+
+board/efi/efi-x86_app/efi.c
+	x86 board code for running as an EFI application
+
+board/efi/efi-x86_payload
+	generic x86 EFI payload board support code
+
+common/cmd_efi.c
+	the 'efi' command
+
+--
+Ben Stoltz, Simon Glass
+Google, Inc
+July 2015
+
+[1] http://www.qemu.org
+[2] http://www.tianocore.org/ovmf/
diff --git a/doc/uefi/uefi.rst b/doc/uefi/uefi.rst
new file mode 100644
index 0000000000..476117bfc5
--- /dev/null
+++ b/doc/uefi/uefi.rst
@@ -0,0 +1,334 @@
+.. SPDX-License-Identifier: GPL-2.0+
+.. Copyright (c) 2018 Heinrich Schuchardt
+
+UEFI on U-Boot
+==============
+
+The Unified Extensible Firmware Interface Specification (UEFI) [1] has become
+the default for booting on AArch64 and x86 systems. It provides a stable API for
+the interaction of drivers and applications with the firmware. The API comprises
+access to block storage, network, and console to name a few. The Linux kernel
+and boot loaders like GRUB or the FreeBSD loader can be executed.
+
+Development target
+------------------
+
+The implementation of UEFI in U-Boot strives to reach the requirements described
+in the "Embedded Base Boot Requirements (EBBR) Specification - Release v1.0"
+[4]. The "Server Base Boot Requirements System Software on ARM Platforms" [5]
+describes a superset of the EBBR specification and may be used as further
+reference.
+
+A full blown UEFI implementation would contradict the U-Boot design principle
+"keep it small".
+
+Building U-Boot for UEFI
+------------------------
+
+The UEFI standard supports only little-endian systems. The UEFI support can be
+activated for ARM and x86 by specifying::
+
+    CONFIG_CMD_BOOTEFI=y
+    CONFIG_EFI_LOADER=y
+
+in the .config file.
+
+Support for attaching virtual block devices, e.g. iSCSI drives connected by the
+loaded UEFI application [3], requires::
+
+    CONFIG_BLK=y
+    CONFIG_PARTITIONS=y
+
+Executing a UEFI binary
+~~~~~~~~~~~~~~~~~~~~~~~
+
+The bootefi command is used to start UEFI applications or to install UEFI
+drivers. It takes two parameters::
+
+    bootefi <image address> [fdt address]
+
+* image address - the memory address of the UEFI binary
+* fdt address - the memory address of the flattened device tree
+
+Below you find the output of an example session starting GRUB::
+
+    => load mmc 0:2 ${fdt_addr_r} boot/dtb
+    29830 bytes read in 14 ms (2 MiB/s)
+    => load mmc 0:1 ${kernel_addr_r} efi/debian/grubaa64.efi
+    reading efi/debian/grubaa64.efi
+    120832 bytes read in 7 ms (16.5 MiB/s)
+    => bootefi ${kernel_addr_r} ${fdt_addr_r}
+
+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.
+
+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::
+
+    bootefi bootmgr [fdt address]
+
+As of U-Boot v2018.03 UEFI variables are not persisted and cannot be set at
+runtime.
+
+Executing the built in hello world application
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+A hello world UEFI application can be built with::
+
+    CONFIG_CMD_BOOTEFI_HELLO_COMPILE=y
+
+It can be embedded into the U-Boot binary with::
+
+    CONFIG_CMD_BOOTEFI_HELLO=y
+
+The bootefi command is used to start the embedded hello world application::
+
+    bootefi hello [fdt address]
+
+Below you find the output of an example session::
+
+    => bootefi hello ${fdtcontroladdr}
+    ## Starting EFI application at 01000000 ...
+    WARNING: using memory device/image path, this may confuse some payloads!
+    Hello, world!
+    Running on UEFI 2.7
+    Have SMBIOS table
+    Have device tree
+    Load options: root=/dev/sdb3 init=/sbin/init rootwait ro
+    ## Application terminated, r = 0
+
+The environment variable fdtcontroladdr points to U-Boot's internal device tree
+(if available).
+
+Executing the built-in self-test
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+An UEFI self-test suite can be embedded in U-Boot by building with::
+
+    CONFIG_CMD_BOOTEFI_SELFTEST=y
+
+For testing the UEFI implementation the bootefi command can be used to start the
+self-test::
+
+    bootefi selftest [fdt address]
+
+The environment variable 'efi_selftest' can be used to select a single test. If
+it is not provided all tests are executed except those marked as 'on request'.
+If the environment variable is set to 'list' a list of all tests is shown.
+
+Below you can find the output of an example session::
+
+    => setenv efi_selftest simple network protocol
+    => bootefi selftest
+    Testing EFI API implementation
+    Selected test: 'simple network protocol'
+    Setting up 'simple network protocol'
+    Setting up 'simple network protocol' succeeded
+    Executing 'simple network protocol'
+    DHCP Discover
+    DHCP reply received from 192.168.76.2 (52:55:c0:a8:4c:02)
+      as broadcast message.
+    Executing 'simple network protocol' succeeded
+    Tearing down 'simple network protocol'
+    Tearing down 'simple network protocol' succeeded
+    Boot services terminated
+    Summary: 0 failures
+    Preparing for reset. Press any key.
+
+The UEFI life cycle
+-------------------
+
+After the U-Boot platform has been initialized the UEFI API provides two kinds
+of services
+
+* boot services and
+* runtime services.
+
+The API can be extended by loading UEFI drivers which come in two variants
+
+* boot drivers and
+* runtime drivers.
+
+UEFI drivers are installed with U-Boot's bootefi command. With the same command
+UEFI applications can be executed.
+
+Loaded images of UEFI drivers stay in memory after returning to U-Boot while
+loaded images of applications are removed from memory.
+
+An UEFI application (e.g. an operating system) that wants to take full control
+of the system calls ExitBootServices. After a UEFI application calls
+ExitBootServices
+
+* boot services are not available anymore
+* timer events are stopped
+* the memory used by U-Boot except for runtime services is released
+* the memory used by boot time drivers is released
+
+So this is a point of no return. Afterwards the UEFI application can only return
+to U-Boot by rebooting.
+
+The UEFI object model
+---------------------
+
+UEFI offers a flexible and expandable object model. The objects in the UEFI API
+are devices, drivers, and loaded images. These objects are referenced by
+handles.
+
+The interfaces implemented by the objects are referred to as protocols. These
+are identified by GUIDs. They can be installed and uninstalled by calling the
+appropriate boot services.
+
+Handles are created by the InstallProtocolInterface or the
+InstallMultipleProtocolinterfaces service if NULL is passed as handle.
+
+Handles are deleted when the last protocol has been removed with the
+UninstallProtocolInterface or the UninstallMultipleProtocolInterfaces service.
+
+Devices offer the EFI_DEVICE_PATH_PROTOCOL. A device path is the concatenation
+of device nodes. By their device paths all devices of a system are arranged in a
+tree.
+
+Drivers offer the EFI_DRIVER_BINDING_PROTOCOL. This protocol is used to connect
+a driver to devices (which are referenced as controllers in this context).
+
+Loaded images offer the EFI_LOADED_IMAGE_PROTOCOL. This protocol provides meta
+information about the image and a pointer to the unload callback function.
+
+The UEFI events
+---------------
+
+In the UEFI terminology an event is a data object referencing a notification
+function which is queued for calling when the event is signaled. The following
+types of events exist:
+
+* periodic and single shot timer events
+* exit boot services events, triggered by calling the ExitBootServices() service
+* virtual address change events
+* memory map change events
+* read to boot events
+* reset system events
+* system table events
+* events that are only triggered programmatically
+
+Events can be created with the CreateEvent service and deleted with CloseEvent
+service.
+
+Events can be assigned to an event group. If any of the events in a group is
+signaled, all other events in the group are also set to the signaled state.
+
+The UEFI driver model
+---------------------
+
+A driver is specific for a single protocol installed on a device. To install a
+driver on a device the ConnectController service is called. In this context
+controller refers to the device for which the driver is installed.
+
+The relevant drivers are identified using the EFI_DRIVER_BINDING_PROTOCOL. This
+protocol has has three functions:
+
+* supported - determines if the driver is compatible with the device
+* start - installs the driver by opening the relevant protocol with
+  attribute EFI_OPEN_PROTOCOL_BY_DRIVER
+* stop - uninstalls the driver
+
+The driver may create child controllers (child devices). E.g. a driver for block
+IO devices will create the device handles for the partitions. The child
+controllers  will open the supported protocol with the attribute
+EFI_OPEN_PROTOCOL_BY_CHILD_CONTROLLER.
+
+A driver can be detached from a device using the DisconnectController service.
+
+U-Boot devices mapped as UEFI devices
+-------------------------------------
+
+Some of the U-Boot devices are mapped as UEFI devices
+
+* block IO devices
+* console
+* graphical output
+* network adapter
+
+As of U-Boot 2018.03 the logic for doing this is hard coded.
+
+The development target is to integrate the setup of these UEFI devices with the
+U-Boot driver model. So when a U-Boot device is discovered a handle should be
+created and the device path protocol and the relevant IO protocol should be
+installed. The UEFI driver then would be attached by calling ConnectController.
+When a U-Boot device is removed DisconnectController should be called.
+
+UEFI devices mapped as U-Boot devices
+-------------------------------------
+
+UEFI drivers binaries and applications may create new (virtual) devices, install
+a protocol and call the ConnectController service. Now the matching UEFI driver
+is determined by iterating over the implementations of the
+EFI_DRIVER_BINDING_PROTOCOL.
+
+It is the task of the UEFI driver to create a corresponding U-Boot device and to
+proxy calls for this U-Boot device to the controller.
+
+In U-Boot 2018.03 this has only been implemented for block IO devices.
+
+UEFI uclass
+~~~~~~~~~~~
+
+An UEFI uclass driver (lib/efi_driver/efi_uclass.c) has been created that
+takes care of initializing the UEFI drivers and providing the
+EFI_DRIVER_BINDING_PROTOCOL implementation for the UEFI drivers.
+
+A linker created list is used to keep track of the UEFI drivers. To create an
+entry in the list the UEFI driver uses the U_BOOT_DRIVER macro specifying
+UCLASS_EFI as the ID of its uclass, e.g::
+
+    /* Identify as UEFI driver */
+    U_BOOT_DRIVER(efi_block) = {
+        .name  = "EFI block driver",
+        .id    = UCLASS_EFI,
+        .ops   = &driver_ops,
+    };
+
+The available operations are defined via the structure struct efi_driver_ops::
+
+    struct efi_driver_ops {
+        const efi_guid_t *protocol;
+        const efi_guid_t *child_protocol;
+        int (*bind)(efi_handle_t handle, void *interface);
+    };
+
+When the supported() function of the EFI_DRIVER_BINDING_PROTOCOL is called the
+uclass checks if the protocol GUID matches the protocol GUID of the UEFI driver.
+In the start() function the bind() function of the UEFI driver is called after
+checking the GUID.
+The stop() function of the EFI_DRIVER_BINDING_PROTOCOL disconnects the child
+controllers created by the UEFI driver and the UEFI driver. (In U-Boot v2013.03
+this is not yet completely implemented.)
+
+UEFI block IO driver
+~~~~~~~~~~~~~~~~~~~~
+
+The UEFI block IO driver supports devices exposing the EFI_BLOCK_IO_PROTOCOL.
+
+When connected it creates a new U-Boot block IO device with interface type
+IF_TYPE_EFI, adds child controllers mapping the partitions, and installs the
+EFI_SIMPLE_FILE_SYSTEM_PROTOCOL on these. This can be used together with the
+software iPXE to boot from iSCSI network drives [3].
+
+This driver is only available if U-Boot is configured with
+
+    CONFIG_BLK=y
+    CONFIG_PARTITIONS=y
+
+Links
+-----
+
+* [1] http://uefi.org/specifications - UEFI specifications
+* [2] :doc:`../driver-model/index`
+* [3] :doc:`iscsi`
+* [4] https://github.com/ARM-software/ebbr/releases/download/v1.0/ebbr-v1.0.pdf -
+  Embedded Base Boot Requirements (EBBR) Specification - Release v1.0
+* [5] https://developer.arm.com/docs/den0044/latest/server-base-boot-requirements-system-software-on-arm-platforms-version-11 -
+  Server Base Boot Requirements System Software on ARM Platforms - Version 1.1
--
2.20.1

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