.gitlab-ci.yml: add Qemu tests for MIPS Malta board

[J-u-boot.git] / doc / README.fdt-control

diff --git a/doc/README.fdt-control b/doc/README.fdt-control
index 86bae6816d8a34714da246bfcfae7561d8e25055..424d13fc5b11284fcf0fd36f837316467e74c5fb 100644 (file)
--- a/doc/README.fdt-control
+++ b/doc/README.fdt-control
@@ -1,8 +1,6 @@
+# SPDX-License-Identifier: GPL-2.0+

 #
 # Copyright (c) 2011 The Chromium OS Authors.
 #
 # Copyright (c) 2011 The Chromium OS Authors.

-#
-# SPDX-License-Identifier:     GPL-2.0+
-#

 
 Device Tree Control in U-Boot
 =============================
 
 Device Tree Control in U-Boot
 =============================


@@ -33,12 +31,6 @@ the features of each board in the device tree file, and have a single
 generic source base.
 
 To enable this feature, add CONFIG_OF_CONTROL to your board config file.
 generic source base.
 
 To enable this feature, add CONFIG_OF_CONTROL to your board config file.

-It is currently supported on ARM, x86 and Microblaze - other architectures
-will need to add code to their arch/xxx/lib/board.c file to locate the
-FDT. Alternatively you can enable generic board support on your board
-(with CONFIG_SYS_GENERIC_BOARD) if this is available (as it is for
-PowerPC). For ARM, Tegra and Exynos5 have device trees available for
-common devices.

 
 
 What is a Flat Device Tree?
 
 
 What is a Flat Device Tree?


@@ -64,13 +56,17 @@ In case you are wondering, OF stands for Open Firmware.
 Tools
 -----
 
 Tools
 -----
 

-To use this feature you will need to get the device tree compiler here:
+To use this feature you will need to get the device tree compiler. This is
+provided by U-Boot automatically. If you have a system version of dtc
+(typically in the 'device-tree-compiler' package), it is currently not used.

 
 

-       git://jdl.com/software/dtc.git
+If you want to build your own dtc, it is kept here:
+
+       git://git.kernel.org/pub/scm/utils/dtc/dtc.git

 
 For example:
 
 
 For example:
 

-       $ git clone git://jdl.com/software/dtc.git
+       $ git clone git://git.kernel.org/pub/scm/utils/dtc/dtc.git

        $ cd dtc
        $ make
        $ sudo make install
        $ cd dtc
        $ make
        $ sudo make install


@@ -122,15 +118,24 @@ This should include your CPU or SOC's device tree file, placed in
 arch/<arch>/dts, and then make any adjustments required.
 
 If CONFIG_OF_EMBED is defined, then it will be picked up and built into
 arch/<arch>/dts, and then make any adjustments required.
 
 If CONFIG_OF_EMBED is defined, then it will be picked up and built into

-the U-Boot image (including u-boot.bin).
+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 CONFIG_OF_SEPARATE is defined, then it will be built and placed in

-a u-boot.dtb file alongside u-boot.bin. A common approach is then to
+a u-boot.dtb file alongside u-boot-nodtb.bin. A common approach is then to

 join the two:
 
 join the two:
 

-       cat u-boot.bin u-boot.dtb >image.bin
+       cat u-boot-nodtb.bin u-boot.dtb >image.bin
+
+and then flash image.bin onto your board. Note that U-Boot creates
+u-boot-dtb.bin which does the above step for you also. Resulting
+u-boot.bin is a copy of u-boot-dtb.bin in this case. If you are using
+CONFIG_SPL_FRAMEWORK, then u-boot.img will be built to include the device
+tree binary.

 
 

-and then flash image.bin onto your board.
+If CONFIG_OF_BOARD is defined, a board-specific routine will provide the
+device tree at runtime, for example if an earlier bootloader stage creates
+it and passes it to U-Boot.

 
 If CONFIG_OF_HOSTFILE is defined, then it will be read from a file on
 startup. This is only useful for sandbox. Use the -d flag to U-Boot to
 
 If CONFIG_OF_HOSTFILE is defined, then it will be read from a file on
 startup. This is only useful for sandbox. Use the -d flag to U-Boot to


@@ -138,13 +143,24 @@ specify the file to read.
 
 You cannot use more than one of these options at the same time.
 
 
 You cannot use more than one of these options at the same time.
 

+To use a device tree file that you have compiled yourself, pass
+EXT_DTB=<filename> to 'make', as in:
+
+       make EXT_DTB=boot/am335x-boneblack-pubkey.dtb
+
+Then U-Boot will copy that file to u-boot.dtb, put it in the .img file
+if used, and u-boot-dtb.bin.
+

 If you wish to put the fdt at a different address in memory, you can
 define the "fdtcontroladdr" environment variable. This is the hex
 address of the fdt binary blob, and will override either of the options.
 Be aware that this environment variable is checked prior to relocation,
 when only the compiled-in environment is available. Therefore it is not
 possible to define this variable in the saved SPI/NAND flash
 If you wish to put the fdt at a different address in memory, you can
 define the "fdtcontroladdr" environment variable. This is the hex
 address of the fdt binary blob, and will override either of the options.
 Be aware that this environment variable is checked prior to relocation,
 when only the compiled-in environment is available. Therefore it is not
 possible to define this variable in the saved SPI/NAND flash

-environment, for example (it will be ignored).
+environment, for example (it will be ignored). After relocation, this
+variable will be set to the address of the newly relocated fdt blob.
+It is read-only and cannot be changed. It can optionally be used to
+control the boot process of Linux with bootm/bootz commands.

 
 To use this, put something like this in your board header file:
 
 
 To use this, put something like this in your board header file:
 


@@ -159,6 +175,34 @@ After board configuration is done, fdt supported u-boot can be build in two ways
     $ make DEVICE_TREE=<dts-file-name>
 
 
     $ make DEVICE_TREE=<dts-file-name>
 
 

+Relocation, SPL and TPL
+-----------------------
+
+U-Boot can be divided into three phases: TPL, SPL and U-Boot proper.
+
+The full device tree is available to U-Boot proper, but normally only a subset
+(or none at all) is available to TPL and SPL. See 'Pre-Relocation Support' and
+'SPL Support' in doc/driver-model/design.rst for more details.
+
+
+Using several DTBs in the SPL (CONFIG_SPL_MULTI_DTB)
+----------------------------------------------------
+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.
+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
+containing the board ID for example), it possible to start with a generic DTB
+and then switch over to the right DTB after the detection. For this purpose,
+the platform code must call fdtdec_resetup(). Based on the returned flag, the
+platform may have to re-initiliaze the DM subusystem using dm_uninit() and
+dm_init_and_scan().
+
+

 Limitations
 -----------
 
 Limitations
 -----------