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diff --git a/doc/README.fdt-overlays b/doc/README.fdt-overlays deleted file mode 100644 index 39139cb850..0000000000 --- a/doc/README.fdt-overlays +++ /dev/null @@ -1,114 +0,0 @@ -U-Boot FDT Overlay usage -============================================= - -Overlays Syntax ---------------- - -Overlays require slightly different syntax compared to traditional overlays. -Please refer to dt-object-internal.txt in the dtc sources for information -regarding the internal format of overlays: -https://git.kernel.org/pub/scm/utils/dtc/dtc.git/tree/Documentation/dt-object-internal.txt - -Building Overlays ------------------ - -In a nutshell overlays provides a means to manipulate a symbol a previous dtb -or overlay has defined. It requires both the base and all the overlays -to be compiled with the -@ command line switch so that symbol information is -included. - -Note support for -@ option can only be found in dtc version 1.4.4 or newer. -Only version 4.14 or higher of the Linux kernel includes a built in version -of dtc that meets this requirement. - -Building an overlay follows the same process as building a traditional dtb. - -For example: - -base.dts --------- - - /dts-v1/; - / { - foo: foonode { - foo-property; - }; - }; - - $ dtc -@ -I dts -O dtb -o base.dtb base.dts - -bar.dts -------- - - /dts-v1/; - /plugin/; - / { - fragment@1 { - target = <&foo>; - __overlay__ { - overlay-1-property; - bar: barnode { - bar-property; - }; - }; - }; - }; - - $ dtc -@ -I dts -O dtb -o bar.dtb bar.dts - -Ways to Utilize Overlays in U-boot ----------------------------------- - -There are two ways to apply overlays in U-boot. -1. Include and define overlays within a FIT image and have overlays - automatically applied. - -2. Manually load and apply overlays - -The remainder of this document will discuss using overlays via the manual -approach. For information on using overlays as part of a FIT image please see: -doc/uImage.FIT/overlay-fdt-boot.txt - -Manually Loading and Applying Overlays --------------------------------------- - -1. Figure out where to place both the base device tree blob and the -overlay. Make sure you have enough space to grow the base tree without -overlapping anything. - -=> setenv fdtaddr 0x87f00000 -=> setenv fdtovaddr 0x87fc0000 - -2. Load the base blob and overlay blobs - -=> load ${devtype} ${bootpart} ${fdtaddr} ${bootdir}/base.dtb -=> load ${devtype} ${bootpart} ${fdtovaddr} ${bootdir}/overlay.dtb - -3. Set it as the working fdt tree. - -=> fdtaddr $fdtaddr - -4. Grow it enough so it can 'fit' all the applied overlays - -=> fdt resize 8192 - -5. You are now ready to apply the overlay. - -=> fdt apply $fdtovaddr - -6. Boot system like you would do with a traditional dtb. - -For bootm: - -=> bootm ${kerneladdr} - ${fdtaddr} - -For bootz: - -=> bootz ${kerneladdr} - ${fdtaddr} - -Please note that in case of an error, both the base and overlays are going -to be invalidated, so keep copies to avoid reloading. - -Pantelis Antoniou -pantelis.antoniou@konsulko.com -11/7/2017 |