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doc: devicetree: Align documentation to use Kconfig options

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Since U-Boot switched away from manual CONFIG_* defines to Kconfig
options, align devicetree documentation accordingly.

Signed-off-by: Sumit Garg <sumit.garg@linaro.org>
This commit is contained in:
Sumit Garg
2024-02-29 22:24:05 -05:00
committed by Tom Rini
parent b841ca6ae6
commit 0bd96eea3d
1 changed files with 22 additions and 26 deletions
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doc/develop/devicetree/control.rst
+22 -26
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@@ -29,7 +29,7 @@ a number of similar boards with different peripherals, you can describe
the features of each board in the devicetree file, and have a single
generic source base.
To enable this feature, add CONFIG_OF_CONTROL to your board config file.
To enable this feature, select `OF_CONTROL` via Kconfig.
What is a Flattened Devicetree?
@@ -81,12 +81,8 @@ Failing that, you could write one from scratch yourself!
Configuration
-------------
Use::
#define CONFIG_DEFAULT_DEVICE_TREE "<name>"
to set the filename of the devicetree source. Then put your devicetree
file into::
Set up "<name>" when prompted for `DEFAULT_DEVICE_TREE` by Kconfig. Then put
your devicetree file into::
arch/<arch>/dts/<name>.dts
@@ -94,24 +90,24 @@ This should include your CPU or SOC's devicetree file, placed in
`arch/<arch>/dts`, and then make any adjustments required using a u-boot-dtsi
file for your board.
If CONFIG_OF_EMBED is defined, then it will be picked up and built into
If `OF_EMBED` is selected by Kconfig, then it will be picked up and built into
the U-Boot image (including u-boot.bin). This is suitable for debugging
and development only and is not recommended for production devices.
If CONFIG_OF_SEPARATE is defined, then it will be built and placed in
If `OF_SEPARATE` is selected by Kconfig, then it will be built and placed in
a u-boot.dtb file alongside u-boot-nodtb.bin with the combined result placed
in u-boot.bin so you can still just flash u-boot.bin onto your board. If you are
using CONFIG_SPL_FRAMEWORK, then u-boot.img will be built to include the device
tree binary.
in u-boot.bin so you can still just flash u-boot.bin onto your board. If Kconfig
option `SPL_FRAMEWORK` is enabled, then u-boot.img will be built to include the
device tree binary.
If CONFIG_OF_BOARD is defined, a board-specific routine will provide the
If `OF_BOARD` is selected by Kconfig, a board-specific routine will provide the
devicetree at runtime, for example if an earlier bootloader stage creates
it and passes it to U-Boot.
If CONFIG_BLOBLIST is defined, the devicetree may come from a bloblist passed
from a previous stage, if present.
If `BLOBLIST` is selected by Kconfig, the devicetree may come from a bloblist
passed from a previous stage, if present.
If CONFIG_SANDBOX is defined, then it will be read from a file on
If `SANDBOX` is selected by Kconfig, then it will be read from a file on
startup. Use the -d flag to U-Boot to specify the file to read, -D for the
default and -T for the test devicetree, used to run sandbox unit tests.
@@ -145,7 +141,7 @@ Build:
After the board configuration is done, fdt supported u-boot can be built in two
ways:
# build the default dts which is defined from CONFIG_DEFAULT_DEVICE_TREE::
# build the default dts which is selected by DEFAULT_DEVICE_TREE Kconfig::
$ make
@@ -198,8 +194,8 @@ As mentioned above, the U-Boot build system automatically includes a
`*-u-boot.dtsi` file, if found, containing U-Boot specific
quirks. However, some data, such as the mentioned public keys, are not
appropriate for upstream U-Boot but are better kept and maintained
outside the U-Boot repository. You can use CONFIG_DEVICE_TREE_INCLUDES
to specify a list of .dtsi files that will also be included when
outside the U-Boot repository. You can use `DEVICE_TREE_INCLUDES` Kconfig
option to specify a list of .dtsi files that will also be included when
building .dtb files.
@@ -213,14 +209,14 @@ The full devicetree is available to U-Boot proper, but normally only a subset
'SPL Support' in doc/driver-model/design.rst for more details.
Using several DTBs in the SPL (CONFIG_SPL_MULTI_DTB)
----------------------------------------------------
Using several DTBs in the SPL (SPL_MULTI_DTB_FIT Kconfig option)
----------------------------------------------------------------
In some rare cases it is desirable to let SPL be able to select one DTB among
many. This usually not very useful as the DTB for the SPL is small and usually
fits several platforms. However the DTB sometimes include information that do
work on several platforms (like IO tuning parameters).
In this case it is possible to use CONFIG_SPL_MULTI_DTB. This option appends to
the SPL a FIT image containing several DTBs listed in SPL_OF_LIST.
In this case it is possible to use SPL_MULTI_DTB_FIT Kconfig option. This option
appends to the SPL a FIT image containing several DTBs listed in SPL_OF_LIST.
board_fit_config_name_match() is called to select the right DTB.
If board_fit_config_name_match() relies on DM (DM driver to access an EEPROM
@@ -247,10 +243,10 @@ architectures.
It is important to understand that the fdt only selects options
available in the platform / drivers. It cannot add new drivers (yet). So
you must still have the CONFIG option to enable the driver. For example,
you need to define CONFIG_SYS_NS16550 to bring in the NS16550 driver,
you must still have the Kconfig option to enable the driver. For example,
you need to enable SYS_NS16550 Kconfig option to bring in the NS16550 driver,
but can use the fdt to specific the UART clock, peripheral address, etc.
In very broad terms, the CONFIG options in general control *what* driver
In very broad terms, the Kconfig options in general control *what* driver
files are pulled in, and the fdt controls *how* those files work.
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