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Diffstat (limited to 'doc/README.fdt-overlays')
| -rw-r--r-- | doc/README.fdt-overlays | 37 |
1 files changed, 37 insertions, 0 deletions
diff --git a/doc/README.fdt-overlays b/doc/README.fdt-overlays new file mode 100644 index 0000000000..ee868eca36 --- /dev/null +++ b/doc/README.fdt-overlays @@ -0,0 +1,37 @@ +U-Boot FDT Overlay usage (without FIT images) +============================================= + +FDT overlays are now available for use even without FIT images. +It is not as automagic as with FIT images though and require a few +manual steps. + +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 + +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 |