On 1/10/24 11:35, Sumit Garg wrote:
Changes in v4:
- Switched subtree to be imported as dts/upstream sub-directory rather than devicetree-rebasing sub-directory to better suite U-Boot directory structure.
- Since we now have v6.7-dts tag available now, so switch subtree to that from its beginning.
- Patch #2: Incorporate build fix to adjust Bindings Makefile rules to old U-Boot Kbuild infrastructure.
- Patch #3: Incorporate fix to resolve rk3399 migration issue reported by Simon.
- Patch #4: New patch to reuse upstream DT includes by U-Boot as per Brian's use-case for TI K3 SoCs.
- Patch #5: Added a note to OF_UPSTREAM Kconfig option.
- Patch #6: New patch to add script dts/update-dts-subtree.sh as per Rob's comments.
- Patch #7: Separate patch to align documentation to use Kconfig symbols instead.
- Patch #8: Clarify subtree uprev schedule as a separate documentation section. Also, fixed documentation typos.
- Patch #9: Added commit description.
Changes in v3:
- Patch #4: Minor commit message update
- Patch #5: Replace CONFIG_* with Kconfig options
- Patch #7: Dropped Makefile portion and enabled OF_UPSTREAM for SoC instead.
- Patch #1, #3, #6 and #8: Picked up review tags
Changes in v2:
- Patch #1: excluded gitab CI config check and added commit description.
- Patch #3: s/UBOOT_DTSI_LOC/u_boot_dtsi_loc/
- Patch #4: s/DEVICE_TREE_LOC/dt_dir/ and s/U-boot/U-Boot/
- Patch #5: s/U-boot/U-Boot/
- Patch #6 and #7: Picked up review tags
Prerequisite
This patch series requires devicetree-rebasing git repo to be added as a subtree to the main U-Boot repo via:
$ git subtree add --prefix dts/upstream \ git://git.kernel.org/pub/scm/linux/kernel/git/devicetree/devicetree-rebasing.git \ v6.7-dts --squash
Background
This effort started while I was reviewing patch series corresponding to Qcom platforms [1] which was about to import modified devicetree source files from Linux kernel. I suppose keeping devicetree files sync with Linux kernel without any DT bindings schema validation has been a pain for U-Boot SoC/platform maintainers. There has been past discussions about a single DT repo but that hasn't come up and Linux kernel remained the place where DT source files as well as bindings are placed and maintained.
However, Linux kernel DT maintainers proposed [2] for U-Boot to rather use devicetree-rebasing repo [3] which is a forked copy from Linux kernel for DT source files as well as bindings. It is tagged at every Linux kernel major release or intermideate release candidates. So here I have tried to reuse that to bring DT bingings compliance as well as a standard way to maintain a regular sync of DT source files with Linux kernel.
In order to maintain devicetree files sync, U-Boot will maintains a Git subtree for devicetee-rebasing repo as `dts/upstream` sub-directory. U-Boot will regularly sync `dts/upstream/` subtree whenever the next window opens with the next available kernel major release. `dts/update-dts-subtree.sh` script provides a wrapper around git subtree pull command, usage from the top level U-Boot source tree, run:
$ ./dts/update-dts-subtree.sh <devicetree-rebasing-release-tag>
The RFC/prototype for this series has been discussed with Linux DT maintainers as well as U-Boot maintainers here [4]. Now we would like to reach out to wider U-Boot community to seek feedback.
I very much agree with the direction this is going in, but I do have two simple questions:
How do you propose to handle fixes to DTs which are applied to linux-stable releases ? For example, if Linux 6.6(.0) ships a DT which has some defect that is fixed in 6.6.1, how will that fix get into U-Boot DTs ?
Assume that there is some large breaking change in Linux 6.(n+1), something which would be problematic for specific U-Boot platform (e.g. i.MX) or would require a lot of work to sort out, will there be a way to temporarily pin DTs for specific platform to older DT version until that is resolved (e.g. pin to 6.n) ?