[Buildroot] [PATCH] board/khadas/vim3: add the path of the devicetree in extlinux.conf

[Antoine Coutant]

Without this patch, the devicetree used by linux at runtime is
the u_boot devicetree.

While using rusticl on the khadas vim3 board with the default
extlinux.conf, mesa's panfrost driver return "gpu shed timeout"
errors. Adding "devicetree /meson-g12b-khadas-vim3.dtb" to the
extlinux.conf file solve the problem. Linux successfully boot
with and without the change but without this patch the devicetree
used by linux at runtime is the u-boot devicetree.

The differences between the u-boot devicetree and the linux
devicetree are:
-The u-boot devicetree contains two more nodes than the linux devicetree. Those nodes are:
    - smbios : compatible option is set to "u-boot,sysinfo-smbios".
    - __symbols__ : present if -@ or --symbols is used during the devicetree compilation.
-Most of u-boot devicetree nodes have a "phandle" property.
-SoC and vpu have a "u-boot,dm-pre-reloc;" property.
-Some aliases are different.
-The u-boot operating points tables contains more nodes.
The size difference between the u-boot devicetree and the linux
devicetree is approximately 3.5kB.

During runtime, the linux devicetree have the "phandle" and
"u-boot,dm-pre-reloc;" properties and the smbios node. So,
The runtime devicetree is the one from u-boot.

Signed-off-by: Antoine Coutant <antoine.coutant at smile.fr>
---

Without this patch, there is 18 lines modified in the runtime
devicetree compared to the u-boot devicetree. These 18 same lines
are also modified in the runtime devicetree with this patch
compared to the linux devicetree. Those lines may be modified by
u-boot during the boot process.
The 18 lines added/modified by u-boot during the boot process are:
-The comments about the device tree characteristics are modified.
-The memreserve is added.
-A serial number is added.
-The u-boot version is added.
-The bootargs are added.
-The CVBS framebuffer is enabled.
-The local-mac-address is set.
-The memory size is modified.
---
 board/khadas/vim3/extlinux.conf | 1 +
 1 file changed, 1 insertion(+)

diff --git a/board/khadas/vim3/extlinux.conf b/board/khadas/vim3/extlinux.conf
index fede99b502..2b1544a5cc 100644
--- a/board/khadas/vim3/extlinux.conf
+++ b/board/khadas/vim3/extlinux.conf
@@ -1,4 +1,5 @@
 default buildroot
 label buildroot
    kernel /Image
+   devicetree /meson-g12b-a311d-khadas-vim3.dtb
 append root=/dev/mmcblk0p2 rootwait console=ttyAML0,115200
-- 
2.25.1