Adding device tree parameter to I2C bus

[otiv-jerome-colle]

Hi all,

I realise there's been some similar questions on here, but I'm having a bit of trouble finding the correct way to do this as I'm relatively new to this.

I would like to add a parameter to an I2C node in our device tree. In the flash directory, I've looked at the DTB being used, which is tegra234-p3768-0000+p3767-0001-nv.dtb. Now I've decompiled that one, patched it, and added a recipe for nvidia-kernel-oot_36.3.0.bbappend. This fails because tegra234-p3768-0000+p3767-0001-nv.dts can't be found.

We're using a custom board, so we have the flashvars files where we add our custom pinmux files. In the flashvars file there seems to be an OVERLAY_DTB_FILE entry. Is it better to use an overlay for this? The change is permanent and can happen at build time.

Then I also saw some answers pointing to tegrademo-devicetree.

I've explored these three paths, and I'm wondering which one (if any) of the three is most applicable to this situation. Are there any examples I could follow?

Thanks in advance!

[otiv-jerome-colle]

Update: installing a manually compiled .dtso file next to the pinmux files and adding it to flashvars doesn't work. The file doesn't get installed to the tegraflash directory.

In recipes-bsp:

tegra-binaries
│   ├── tegra-binaries
│   │   ├── tegra234-custom-i2c-overlay.dtbo
│   │   ├── tegra234-p3768-0000-p3767-0001-gpio-default.dtsi
│   │   ├── tegra234-p3768-0000-p3767-0001-padvoltage-default.dtsi
│   │   └── tegra234-p3768-0000-p3767-0001-pinmux.dtsi
│   ├── tegra-binaries_36.3.0.bbappend
│   ├── tegra-bootfiles_36.3.0.bbappend
│   ├── tegra-flashvars
│   │   └── p3767_flashvars
│   └── tegra-flashvars_36.3.0.bbappend

tegra-binaries_36.3.0.bbappend:

FILESEXTRAPATHS:prepend := "${THISDIR}/${PN}:"

SRC_URI += "\
    file://tegra234-p3768-0000-p3767-0001-gpio-default.dtsi \
    file://tegra234-p3768-0000-p3767-0001-padvoltage-default.dtsi \
    file://tegra234-p3768-0000-p3767-0001-pinmux.dtsi \
    file://tegra234-custom-i2c-overlay.dtbo \
"

tegra-bootfiles_36.3.0.bbappend:

o_install:append:tegra234() {
    install -d ${D}${datadir}/tegraflash
    install -m 0644 ${S}/../tegra234-p3768-0000-p3767-0001-gpio-default.dtsi ${D}${datadir}/tegraflash/
    install -m 0644 ${S}/../tegra234-p3768-0000-p3767-0001-padvoltage-default.dtsi ${D}${datadir}/tegraflash/
    install -m 0644 ${S}/../tegra234-p3768-0000-p3767-0001-pinmux.dtsi ${D}${datadir}/tegraflash/
    install -m 0644 ${S}/../tegra234-custom-i2c-overlay.dtbo ${D}${datadir}/tegraflash/
}

p3767_flashvars:

FLASHVARS="PMIC_CONFIG TBCDTB_FILE"
OVERLAY_DTB_FILE="tegra234-custom-i2c-overlay.dtbo"
CHIPID=0x23
PLUGIN_MANAGER_OVERLAYS="tegra234-carveouts.dtbo,tegra-optee.dtbo,tegra234-p3768-0000+p3767-0000-dynamic.dtbo"
BPFDTB_FILE="tegra234-bpmp-3767-0001-3509-a02.dtb"
BPF_FILE="bpmp_t234-TE980M-A1_prod.bin"
BR_CMD_CONFIG="tegra234-mb1-bct-reset-p3767-0000.dts"
DEVICEPROD_CONFIG="tegra234-mb1-bct-cprod-p3767-0000.dts"
DEVICE_CONFIG="tegra234-mb1-bct-device-p3767-0000.dts"
DEV_PARAMS="tegra234-br-bct-p3767-0000-l4t.dts"
DEV_PARAMS_B="tegra234-br-bct_b-p3767-0000-l4t.dts"
EMC_FUSE_DEV_PARAMS="tegra234-br-bct-diag-boot.dts"
GPIOINT_CONFIG="tegra234-mb1-bct-gpioint-p3767-0000.dts"
MB2BCT_CFG="tegra234-mb2-bct-misc-p3767-0000-antmicro-job.dts"
MINRATCHET_CONFIG="--minratchet_config tegra234-mb1-bct-ratchet-p3767-0000.dts"
MISC_CONFIG="tegra234-mb1-bct-misc-p3767-0000.dts"
PINMUX_CONFIG="tegra234-p3768-0000-p3767-0001-pinmux.dtsi"
PMC_CONFIG="tegra234-p3768-0000-p3767-0001-padvoltage-default.dtsi"
PMIC_CONFIG="tegra234-mb1-bct-pmic-p3767-0000-@[email protected]"
PROD_CONFIG="tegra234-mb1-bct-prod-p3767-0000.dts"
SCR_CONFIG="tegra234-mb2-bct-scr-p3767-0000.dts"
TBCDTB_FILE="@DTBFILE@"
UPHY_CONFIG="--uphy tegra234-mb1-bct-uphylane-si.dtsi"
WB0SDRAM_BCT="tegra234-p3767-0001-wb0sdram-l4t.dts"

So all the .dtsi files get put into tegraflash correctly, but the .dtbo files don't. Cheating and changing the extension to .dtsi puts it there correctly.

What am I doing wrong here? Does the OVERLAY_DTB_FILE entry expect a source file? If so, it seems like its not being overlayed onto the final device tree.

[madisongh]

Are you trying to modify the device tree used by the kernel, or one of the ones used by the bootloaders? Your OP talked about the kernel device tree, but the later post is talking about the bootloader ones.

If it's the device tree for the kernel, it's probably easier to use devtool to help generate a patch to the device tree source file(s).

If you really want to use a DTB overlay for this, and you have it set up the right way for getting applied by the bootloader at boot time, then you should stage the .dtbo file either to ${DEPLOY_DIR_IMAGE} or under the ${EXTERNAL_KERNEL_DEVICETREE} directory, and add the name of that overlay file to the TEGRA_PLUGIN_MANAGER_OVERLAYS variable in your machine configuration. The copy_dtb_overlays function in image_types_tegra.bbclass has the logic for populating overlays into the tegraflash package.

[otiv-jerome-colle]

I was indeed trying to modify the one used by the kernel, still starting to lean about all of this.

Applying the patch in nvidia-kernel-oot did the trick! Many thanks!