From d80162cfc559491dee3009b120e7268e9388302f Mon Sep 17 00:00:00 2001 From: Pantelis Antoniou Date: Mon, 4 Sep 2017 23:12:18 +0300 Subject: [PATCH] doc: Document how to apply fdt overlays MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit We have the capability to apply overlays on the command line but we didn't have a document explaining how. Signed-off-by: Pantelis Antoniou Reviewed-by: Łukasz Majewski Acked-by: Simon Glass --- doc/README.fdt-overlays | 37 +++++++++++++++++++++++++++++++++++++ 1 file changed, 37 insertions(+) create mode 100644 doc/README.fdt-overlays diff --git a/doc/README.fdt-overlays b/doc/README.fdt-overlays new file mode 100644 index 0000000..ee868ec --- /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