On Fri, Sep 27, 2024 at 1:19 AM Marek Vasut marex@denx.de wrote:
On 9/27/24 12:53 AM, Lothar Rubusch wrote:
On Thu, Sep 26, 2024 at 3:36 AM Marek Vasut marex@denx.de wrote:
On 9/26/24 12:49 AM, Lothar Rubusch wrote:
Hi,
[...]
Shall I add the files to my DTS patches and ask for upstreaming of the handoff files into the kernel?
Are the handoff files really used by Linux for anything , or do they contain various clock/pinmux/DRAM settings only used by U-Boot ? If the later, place them into U-Boot and include them from -u-boot.dtsi file.
Similar to the other socfpga targets, the handoff files are just relevant to u-boot. So, I'll keep them in arch/arm/dts.
Right
My particular situation then is as follows. The .dts file just includes several .dtsi files. I place this .dts file into arch/arm/dts. The first includes contain the "handoff setup". Then I include adjustments (.dtsi fragments) to the selected base-board and boot-mode. Both can vary that's why I really would prefer to allow for a Kconfig option on that, in contrary to provide a set of .dts files for all possible combinations.
Example: $ cat ./arch/arm/dts/socfpga_arria10_mercury_aa1_pe1_sdmmc-u-boot.dts
Upstream DT named this way into Linux:
socfpga_arria10_mercury_aa1_pe1_sdmmc.dts
And then in U-Boot, implement the extras which include whatever you need, name the file:
socfpga_arria10_mercury_aa1_pe1_sdmmc-u-boot.dtsi
The U-Boot build system will combine the two DTs, the build system should automatically append matching -u-boot.dtsi content to any .dts file.
I am not sure if this also works if the .dts file is in dts/upstream/* while the -u-boot.dtsi is in arch/*/dts/ , but there is now definitely a use case for such a setup, it is probably a matter of tweaking the Makefiles .
/dts-v1/; /* will be taken from /arch/arm/dts */ #include "socfpga_arria10_mercury_aa1_handoff.h" #include "socfpga_arria10-handoff.dtsi" #include "socfpga_arria10_handoff_u-boot.dtsi"
/* will be taken from /dts/upstream */ #include "../../../dts/upstream/src/arm/intel/socfpga/socfpga_arria10_mercury_aa1.dtsi" #include "../../../dts/upstream/src/arm/intel/socfpga/socfpga_enclustra_mercury_bootmode_sdmmc.dtsi" #include "../../../dts/upstream/src/arm/intel/socfpga/socfpga_enclustra_mercury_pe1.dtsi"
Ideally, now I like to have the first part as default device tree. DEFAULT_DEVICE_TREE=socfpga_arria10_mercury_aa1_pe1_sdmmc-u-boot.dts When doing so, I noticed I cannot enable CONFIG_OF_UPSTREAM anymore, the files in arch/arm/dts won't be found anymore. Then I have the issue how to access the generic .dtsi files used for boot-mode or base board. These files are identical to the kernel DT why I would prefer to use them from dts/upstream. Including them like ../../../../../... works, but... I think there must be a better way.
Look at how the -u-boot.dtsi are automatically added on top of .dts files, that might be a start.
Ideally I like to setup some Kconfig choice for base board selection and one for boot-mode.
1.) In the documentation control.rst I read that the u-boot.dts is combined of several elements. Is there a way to take this base .dts, then add a base board .dtsi by Kconfig option, and similar a boot-mode?
The -u-boot.dtsi is preprocessed by C preprocessor, just like all the other DTs, so you can have a -u-boot.dtsi file which contains C preprocessor conditional statements in it to conditionally include other .dtsi files:
#if IS_ENABLED(...) #include ... #else ... ... #endif
Going through the include list setup by the Makefile made me find my mistake. Currently I may use u-boot specific stuff in arch/arm/dts and include generic .dtsi fragments from dts/upstream. Note: I'm not setting CONFIG_OF_UPSTREAM since I'm using the regular include list which already contains dts/upstream/src/arm/intel. Is this ok? Or, shall I try a different approach, which involves having CONFIG_OF_UPSTREAM explicitely set in the defconfig?
3.) What would be the best possibility to have a u-boot.dts with handoff setup in arch/arm/dts and append .dtsi files from the general dts/upstream - in case are there other boards are doing something similar?
See above, maybe some of it helps.
Yes. This helped. I can set base-board and boot mode now by Kconfig option with a generic .dts file. Note, it may still take some time, since I'd like to test the stuff still a bit on hardware before submitting something to the list.