Am Freitag, 13. Oktober 2017, 12:10:47 CEST schrieb Andreas Färber:
Am 13.10.2017 um 11:22 schrieb Alexander Graf:
On 13.10.17 11:17, Frank Kunz wrote:
I'm doing some test with EFI boot on an olinuxino board here: https:// build.opensuse.org/package/show/home:frank_kunz:branches:openSUSE:Factory :ARM/ JeOS-olinuxinolime
The image works and the kernel has a device-tree visible under /proc/device- tree. With non EFI configurations the device-tree is loaded by uboot from the boot partition dtb directory and is then passed to the kernel by boot command. For EFI there is no dtb directory. Also I haven't found a *.dtb file on the filesystem anywhere.
How does the kernel get the device-tree in EFI boot mode?
It gets it from either a device tree that gets loaded from /boot/dtb or if none is found from the built-in device tree that U-Boot contains.
I successfully tried that by compiling a dtb file out of the upstream kernel tree and copied it to the target board. U-boot then u-boot tries to load the file from the first partition, which is the EFI partition. So then the correct path on Linux is then /boot/efi/dtb.
The background is that some hardware specific configurations need to be done per use case in the device-tree. E.g. adding a battery or a touch screen. Without the device-tree settings the kernel will not probe the devices. Enabling that on u-boot boot mode can be done by either modifying the device-tree file or create overlays and load them by u-boot script with "fdt apply" command. How can this be configured in EFI mode?
There are a couple of approaches. I think by now you can add dt overlays on demand even after the kernel is loaded, so you could just have a systemd service adding them for you.
Please provide proof of such a feature - I don't believe it's in 4.13, and I haven't noticed it in 4.14-rc yet. Patchsets have been around for a long time...
Depending on what overlay operation is desired, fdt apply could just operate on $fdtcontroladdr for the internal tree today.
So far the only some u-boot configurations have the OF_LIBFDT_OVERLAY configuration set. Without that the "fdt apply" command is not supported. Also the distroboot environment is not supporting "fdt apply" yet. I think with that, for the moment, supporting fdt overlays would be then a opensuse specific configuration in boot.scr. That is then similar as raspibian and armbian are doing it. They read a *Env.txt file which contains a list of overlay file names. Br, Frank -- To unsubscribe, e-mail: opensuse-arm+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse-arm+owner@opensuse.org