From mboxrd@z Thu Jan 1 00:00:00 1970 From: bugzilla at busybox.net Date: Tue, 05 Feb 2019 10:06:37 +0000 Subject: [Buildroot] [Bug 11656] Device tree issues with BeagleBoneBlack and LCD cape In-Reply-To: References: Message-ID: List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: buildroot@busybox.net https://bugs.busybox.net/show_bug.cgi?id=11656 --- Comment #1 from Tibor Stolz --- Created attachment 7941 --> https://bugs.busybox.net/attachment.cgi?id=7941&action=edit Device tree customization for the LCD cape Hello, I finally succeeded in building a Buildroot system that properly supports the gen4-4DCAPE-43T LCD screen. However, it required some "tricks" which are not properly supported by the Buildroot workflow. First of all, the "dtc -I fs /proc/device-tree -o my-device-tree.dts" approach of getting the device tree from a running Debian system was rubbish. To quote #beagle IRC: > it's definitely not something that's intended to work in the first place > [...] > /proc/device-tree does not show the original DT as it was passed to the kernel > [...] > some kernel code modifies these data structures Therefore I created the attached device tree source code, which takes the am335x-boneblack.dts as a basis (#include) and adds the definitions from translated from "overlay fragment" syntax to normal dts code (reference: ). This bug now boils down to Buildroot's handling of such out-of-tree device tree files. I included my am335x-withcapes-4d4r.dts in [make menuconfig --> Kernel --> Out-of-tree Device Tree Source file paths]. The problems are as follows: 1) I had to manually add output/build/linux-4.14.96/include/dt-bindings/board/am335x-bbw-bbb-base.h (downloaded from GitHub), after the kernel has been extracted. This is probably a use case outside of the goals of Buildroot, so maybe I'll inline that include file later. 2) When building the Linux kernel, Buildroot will copy my am335x-withcapes-4d4r.dts into output/build/linux-4.14.96/arch/arm/boot/dts/, compile it there, and copy the compiled file to output/images/am335x-withcapes-4d4r.dtb. However, !! the .dtb file is not included in output/images/boot.vfat !! 3) The same problem occurs with a boot.scr file, which I included as of [make menuconfig --> Bootloaders --> Generate a U-Boot boot script: ON] [make menuconfig --> Bootloaders --> U-Boot boot script source: /path/to/boot.scr] The result is that output/images/boot.scr is created, but boot.scr is not part of output/images/boot.vfat! My solution was to manually add am335x-withcapes-4d4r.dtb and boot.scr to the FAT partition once the sdcard.img was written to the SD card. In this configuration, the LCD is now working. I think that problems 2) and 3) are minor bugs of the Buildroot system which should be fixed. Best regards, Tibor Stolz -- You are receiving this mail because: You are on the CC list for the bug.