[PATCH 8/9] doc: Bring in the FIT overlay information
Simon Glass
sjg at chromium.org
Thu Jun 22 22:21:15 CEST 2023
Bring this file into the documentation.
Signed-off-by: Simon Glass <sjg at chromium.org>
---
doc/uImage.FIT/overlay-fdt-boot.txt | 225 ---------------------------
doc/usage/fit/index.rst | 1 +
doc/usage/fit/overlay-fdt-boot.rst | 227 ++++++++++++++++++++++++++++
3 files changed, 228 insertions(+), 225 deletions(-)
delete mode 100644 doc/uImage.FIT/overlay-fdt-boot.txt
create mode 100644 doc/usage/fit/overlay-fdt-boot.rst
diff --git a/doc/uImage.FIT/overlay-fdt-boot.txt b/doc/uImage.FIT/overlay-fdt-boot.txt
deleted file mode 100644
index dddc4db1a67d..000000000000
--- a/doc/uImage.FIT/overlay-fdt-boot.txt
+++ /dev/null
@@ -1,225 +0,0 @@
-U-Boot FDT Overlay FIT usage
-============================
-
-Introduction
-------------
-In many cases it is desirable to have a single FIT image support a multitude
-of similar boards and their expansion options. The same kernel on DT enabled
-platforms can support this easily enough by providing a DT blob upon boot
-that matches the desired configuration.
-
-This document focuses on specifically using overlays as part of a FIT image.
-General information regarding overlays including its syntax and building it
-can be found in doc/README.fdt-overlays
-
-Configuration without overlays
-------------------------------
-
-Take a hypothetical board named 'foo' where there are different supported
-revisions, reva and revb. Assume that both board revisions can use add a bar
-add-on board, while only the revb board can use a baz add-on board.
-
-Without using overlays the configuration would be as follows for every case.
-
- /dts-v1/;
- / {
- images {
- kernel {
- data = /incbin/("./zImage");
- type = "kernel";
- arch = "arm";
- os = "linux";
- load = <0x82000000>;
- entry = <0x82000000>;
- };
- fdt-1 {
- data = /incbin/("./foo-reva.dtb");
- type = "flat_dt";
- arch = "arm";
- };
- fdt-2 {
- data = /incbin/("./foo-revb.dtb");
- type = "flat_dt";
- arch = "arm";
- };
- fdt-3 {
- data = /incbin/("./foo-reva-bar.dtb");
- type = "flat_dt";
- arch = "arm";
- };
- fdt-4 {
- data = /incbin/("./foo-revb-bar.dtb");
- type = "flat_dt";
- arch = "arm";
- };
- fdt-5 {
- data = /incbin/("./foo-revb-baz.dtb");
- type = "flat_dt";
- arch = "arm";
- };
- fdt-6 {
- data = /incbin/("./foo-revb-bar-baz.dtb");
- type = "flat_dt";
- arch = "arm";
- };
- };
-
- configurations {
- default = "foo-reva.dtb;
- foo-reva.dtb {
- kernel = "kernel";
- fdt = "fdt-1";
- };
- foo-revb.dtb {
- kernel = "kernel";
- fdt = "fdt-2";
- };
- foo-reva-bar.dtb {
- kernel = "kernel";
- fdt = "fdt-3";
- };
- foo-revb-bar.dtb {
- kernel = "kernel";
- fdt = "fdt-4";
- };
- foo-revb-baz.dtb {
- kernel = "kernel";
- fdt = "fdt-5";
- };
- foo-revb-bar-baz.dtb {
- kernel = "kernel";
- fdt = "fdt-6";
- };
- };
- };
-
-Note the blob needs to be compiled for each case and the combinatorial explosion of
-configurations. A typical device tree blob is in the low hunderds of kbytes so a
-multitude of configuration grows the image quite a bit.
-
-Booting this image is done by using
-
- # bootm <addr>#<config>
-
-Where config is one of:
- foo-reva.dtb, foo-revb.dtb, foo-reva-bar.dtb, foo-revb-bar.dtb,
- foo-revb-baz.dtb, foo-revb-bar-baz.dtb
-
-This selects the DTB to use when booting.
-
-Configuration using overlays
-----------------------------
-
-Device tree overlays can be applied to a base DT and result in the same blob
-being passed to the booting kernel. This saves on space and avoid the combinatorial
-explosion problem.
-
- /dts-v1/;
- / {
- images {
- kernel {
- data = /incbin/("./zImage");
- type = "kernel";
- arch = "arm";
- os = "linux";
- load = <0x82000000>;
- entry = <0x82000000>;
- };
- fdt-1 {
- data = /incbin/("./foo.dtb");
- type = "flat_dt";
- arch = "arm";
- load = <0x87f00000>;
- };
- fdt-2 {
- data = /incbin/("./reva.dtbo");
- type = "flat_dt";
- arch = "arm";
- load = <0x87fc0000>;
- };
- fdt-3 {
- data = /incbin/("./revb.dtbo");
- type = "flat_dt";
- arch = "arm";
- load = <0x87fc0000>;
- };
- fdt-4 {
- data = /incbin/("./bar.dtbo");
- type = "flat_dt";
- arch = "arm";
- load = <0x87fc0000>;
- };
- fdt-5 {
- data = /incbin/("./baz.dtbo");
- type = "flat_dt";
- arch = "arm";
- load = <0x87fc0000>;
- };
- };
-
- configurations {
- default = "foo-reva.dtb;
- foo-reva.dtb {
- kernel = "kernel";
- fdt = "fdt-1", "fdt-2";
- };
- foo-revb.dtb {
- kernel = "kernel";
- fdt = "fdt-1", "fdt-3";
- };
- foo-reva-bar.dtb {
- kernel = "kernel";
- fdt = "fdt-1", "fdt-2", "fdt-4";
- };
- foo-revb-bar.dtb {
- kernel = "kernel";
- fdt = "fdt-1", "fdt-3", "fdt-4";
- };
- foo-revb-baz.dtb {
- kernel = "kernel";
- fdt = "fdt-1", "fdt-3", "fdt-5";
- };
- foo-revb-bar-baz.dtb {
- kernel = "kernel";
- fdt = "fdt-1", "fdt-3", "fdt-4", "fdt-5";
- };
- bar {
- fdt = "fdt-4";
- };
- baz {
- fdt = "fdt-5";
- };
- };
- };
-
-Booting this image is exactly the same as the non-overlay example.
-u-boot will retrieve the base blob and apply the overlays in sequence as
-they are declared in the configuration.
-
-Note the minimum amount of different DT blobs, as well as the requirement for
-the DT blobs to have a load address; the overlay application requires the blobs
-to be writeable.
-
-Configuration using overlays and feature selection
---------------------------------------------------
-
-Although the configuration in the previous section works is a bit inflexible
-since it requires all possible configuration options to be laid out before
-hand in the FIT image. For the add-on boards the extra config selection method
-might make sense.
-
-Note the two bar & baz configuration nodes. To boot a reva board with
-the bar add-on board enabled simply use:
-
- # bootm <addr>#foo-reva.dtb#bar
-
-While booting a revb with bar and baz is as follows:
-
- # bootm <addr>#foo-revb.dtb#bar#baz
-
-The limitation for a feature selection configuration node is that a single
-fdt option is currently supported.
-
-Pantelis Antoniou
-pantelis.antoniou at konsulko.com
-12/6/2017
diff --git a/doc/usage/fit/index.rst b/doc/usage/fit/index.rst
index 83bc4d01ca42..bd25bd30b284 100644
--- a/doc/usage/fit/index.rst
+++ b/doc/usage/fit/index.rst
@@ -16,3 +16,4 @@ doc/uImage.FIT
signature
verified-boot
beaglebone_vboot
+ overlay-fdt-boot
diff --git a/doc/usage/fit/overlay-fdt-boot.rst b/doc/usage/fit/overlay-fdt-boot.rst
new file mode 100644
index 000000000000..8f8f5e307d26
--- /dev/null
+++ b/doc/usage/fit/overlay-fdt-boot.rst
@@ -0,0 +1,227 @@
+.. SPDX-License-Identifier: GPL-2.0+
+
+U-Boot FDT Overlay FIT usage
+============================
+
+Introduction
+------------
+
+In many cases it is desirable to have a single FIT image support a multitude
+of similar boards and their expansion options. The same kernel on DT enabled
+platforms can support this easily enough by providing a DT blob upon boot
+that matches the desired configuration.
+
+This document focuses on specifically using overlays as part of a FIT image.
+General information regarding overlays including its syntax and building it
+can be found in doc/README.fdt-overlays
+
+Configuration without overlays
+------------------------------
+
+Take a hypothetical board named 'foo' where there are different supported
+revisions, reva and revb. Assume that both board revisions can use add a bar
+add-on board, while only the revb board can use a baz add-on board.
+
+Without using overlays the configuration would be as follows for every case::
+
+ /dts-v1/;
+ / {
+ images {
+ kernel {
+ data = /incbin/("./zImage");
+ type = "kernel";
+ arch = "arm";
+ os = "linux";
+ load = <0x82000000>;
+ entry = <0x82000000>;
+ };
+ fdt-1 {
+ data = /incbin/("./foo-reva.dtb");
+ type = "flat_dt";
+ arch = "arm";
+ };
+ fdt-2 {
+ data = /incbin/("./foo-revb.dtb");
+ type = "flat_dt";
+ arch = "arm";
+ };
+ fdt-3 {
+ data = /incbin/("./foo-reva-bar.dtb");
+ type = "flat_dt";
+ arch = "arm";
+ };
+ fdt-4 {
+ data = /incbin/("./foo-revb-bar.dtb");
+ type = "flat_dt";
+ arch = "arm";
+ };
+ fdt-5 {
+ data = /incbin/("./foo-revb-baz.dtb");
+ type = "flat_dt";
+ arch = "arm";
+ };
+ fdt-6 {
+ data = /incbin/("./foo-revb-bar-baz.dtb");
+ type = "flat_dt";
+ arch = "arm";
+ };
+ };
+
+ configurations {
+ default = "foo-reva.dtb;
+ foo-reva.dtb {
+ kernel = "kernel";
+ fdt = "fdt-1";
+ };
+ foo-revb.dtb {
+ kernel = "kernel";
+ fdt = "fdt-2";
+ };
+ foo-reva-bar.dtb {
+ kernel = "kernel";
+ fdt = "fdt-3";
+ };
+ foo-revb-bar.dtb {
+ kernel = "kernel";
+ fdt = "fdt-4";
+ };
+ foo-revb-baz.dtb {
+ kernel = "kernel";
+ fdt = "fdt-5";
+ };
+ foo-revb-bar-baz.dtb {
+ kernel = "kernel";
+ fdt = "fdt-6";
+ };
+ };
+ };
+
+Note the blob needs to be compiled for each case and the combinatorial explosion of
+configurations. A typical device tree blob is in the low hunderds of kbytes so a
+multitude of configuration grows the image quite a bit.
+
+Booting this image is done by using::
+
+ # bootm <addr>#<config>
+
+Where config is one of::
+
+ foo-reva.dtb, foo-revb.dtb, foo-reva-bar.dtb, foo-revb-bar.dtb,
+ foo-revb-baz.dtb, foo-revb-bar-baz.dtb
+
+This selects the DTB to use when booting.
+
+Configuration using overlays
+----------------------------
+
+Device tree overlays can be applied to a base DT and result in the same blob
+being passed to the booting kernel. This saves on space and avoid the combinatorial
+explosion problem::
+
+ /dts-v1/;
+ / {
+ images {
+ kernel {
+ data = /incbin/("./zImage");
+ type = "kernel";
+ arch = "arm";
+ os = "linux";
+ load = <0x82000000>;
+ entry = <0x82000000>;
+ };
+ fdt-1 {
+ data = /incbin/("./foo.dtb");
+ type = "flat_dt";
+ arch = "arm";
+ load = <0x87f00000>;
+ };
+ fdt-2 {
+ data = /incbin/("./reva.dtbo");
+ type = "flat_dt";
+ arch = "arm";
+ load = <0x87fc0000>;
+ };
+ fdt-3 {
+ data = /incbin/("./revb.dtbo");
+ type = "flat_dt";
+ arch = "arm";
+ load = <0x87fc0000>;
+ };
+ fdt-4 {
+ data = /incbin/("./bar.dtbo");
+ type = "flat_dt";
+ arch = "arm";
+ load = <0x87fc0000>;
+ };
+ fdt-5 {
+ data = /incbin/("./baz.dtbo");
+ type = "flat_dt";
+ arch = "arm";
+ load = <0x87fc0000>;
+ };
+ };
+
+ configurations {
+ default = "foo-reva.dtb;
+ foo-reva.dtb {
+ kernel = "kernel";
+ fdt = "fdt-1", "fdt-2";
+ };
+ foo-revb.dtb {
+ kernel = "kernel";
+ fdt = "fdt-1", "fdt-3";
+ };
+ foo-reva-bar.dtb {
+ kernel = "kernel";
+ fdt = "fdt-1", "fdt-2", "fdt-4";
+ };
+ foo-revb-bar.dtb {
+ kernel = "kernel";
+ fdt = "fdt-1", "fdt-3", "fdt-4";
+ };
+ foo-revb-baz.dtb {
+ kernel = "kernel";
+ fdt = "fdt-1", "fdt-3", "fdt-5";
+ };
+ foo-revb-bar-baz.dtb {
+ kernel = "kernel";
+ fdt = "fdt-1", "fdt-3", "fdt-4", "fdt-5";
+ };
+ bar {
+ fdt = "fdt-4";
+ };
+ baz {
+ fdt = "fdt-5";
+ };
+ };
+ };
+
+Booting this image is exactly the same as the non-overlay example.
+u-boot will retrieve the base blob and apply the overlays in sequence as
+they are declared in the configuration.
+
+Note the minimum amount of different DT blobs, as well as the requirement for
+the DT blobs to have a load address; the overlay application requires the blobs
+to be writeable.
+
+Configuration using overlays and feature selection
+--------------------------------------------------
+
+Although the configuration in the previous section works is a bit inflexible
+since it requires all possible configuration options to be laid out before
+hand in the FIT image. For the add-on boards the extra config selection method
+might make sense.
+
+Note the two bar & baz configuration nodes. To boot a reva board with
+the bar add-on board enabled simply use::
+
+ # bootm <addr>#foo-reva.dtb#bar
+
+While booting a revb with bar and baz is as follows::
+
+ # bootm <addr>#foo-revb.dtb#bar#baz
+
+The limitation for a feature selection configuration node is that a single
+fdt option is currently supported.
+
+.. sectionauthor:: Pantelis Antoniou <pantelis.antoniou at konsulko.com>, 12/6/2017
--
2.41.0.162.gfafddb0af9-goog
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