imx8mp-evk, how to set default device tree?

[LBr]

Hi:

       I'm using an imx8mp-evk with Linux 5.15.71_2.2.0 release.

I'm trying to change u-boot's default dtb file in yocto from "imx8mp-evk-dsp.dtb" to "imx8mp-evk-sof-wm8960.dtb".

So far I have tried the following without luck:

* Created my own layer and added recipes-kernel/linux/linux-imx_%.bbappend with the line KERNEL_DEVICETREE = "freescale/imx8mp-evk-sof-wm8960.dtb" . I can confirm the variable is set by "bitbake virtual/linux -e | grep KERNEL_DEVICETREE", it show the value but not in uboot

* Added the previous line to conf/local.conf

* Added to local.conf:

   First: CONFIG_DEFAULT_FDT_FILE = "imx8mp-evk-sof-wm8960.dtb"

   And then:CONFIG_DEFAULT_DEVICE_TREE="imx8mp-evk-sof-wm8960"

* Used devtool modify u-boot-imx and changed the configuration file imx8mp_evk.h

    -   "fdtfile=" CONFIG_DEFAULT_FDT_FILE "\0" \

    +   "fdtfile=imx8mp-evk-sof-wm8960.dtb\0" \

After updating the recipe, generating the patch, etc, I can see that the patch is correctly applied to uboot's build dir but, once again, the final image still has "fdtfile=imx8mp-evk-dsp.dtb"

I think there is something else setting the default dtb un uboot and so far I was not able to find it, any input is highly appreciated.

[LBr]

Thanks for keep asking me to do the same things I already told you many times that doesn't work instead of verifying for yourself. Very poor service, and from other replies you made to other users I can see it's a pattern...

[Sanket_Parekh]

Hi @LBr ,

I hope you are doing well.

I followed the the below steps mentioned by you in  5.15.71_2.2.0 yocto version.

In my case, default device tree fdtfile is imx8mp-evk.dtb

I was able to change fdtfile value successfully with below changes in imx8mp_evk_defconfig

-CONFIG_DEFAULT_DEVICE_TREE="imx8mp-evk"

+CONFIG_DEFAULT_DEVICE_TREE="imx8mp-custom"

-CONFIG_DEFAULT_FDT_FILE="imx8mp-evk.dtb"
+CONFIG_DEFAULT_FDT_FILE="imx8mp-custom.dtb"

Please make sure that imx8mp-custom.dts is present in /arch/arm/dts and /arch/arm/dts/Makefile is changed accordingly.

One can cross check /build_8mp/tmp/deploy/images/imx8mp-lpddr4-evk/u-boot-imx-initial-env-imx8mp-lpddr4-evk-sd to see if fdtfile variable is changed.

Thanks & Regards,

Sanket Parekh

[LBr]

ps: I know I can just set the right dtb on uboot on the target but I'm trying to set the default dtb so we don't have to change it every time we boot a board

[Sanket_Parekh]

Hi @LBr 

I hope you are doing well.

Please don't change fdtfile env variable in imx8mp_evk.h directly

Instead, change the configuration option in u-boot defconfig as below.

CONFIG_DEFAULT_DEVICE_TREE="imx8mp-evk-sof-wm8960"

CONFIG_DEFAULT_FDT_FILE="imx8mp-evk-sof-wm8960.dtb"

One thing that can override this setting is DEVICE_TREE command line option when compiling.

Please refer to /dts/Kconfig where below description is given.

config DEFAULT_DEVICE_TREE
          string "Default Device Tree for DT control"
          depends on OF_CONTROL
          help
            This option specifies the default Device Tree used for DT control.
             It can be overridden from the command line:
            $ make DEVICE_TREE=<device-tree-name>

In this case,

The default device tree seems to be fdtfile=imx8mp-evk-dsp.dtb

whereas in the imx8mp evk configuration, it is imx8mp-evk.dtb

Please make sure that anything else or yocto variable is not overwriting this configuration.

Thanks & Regards,

Sanket Parekh

[LBr]

Hi Sanket: I have tried your suggestions plus some variations and nothing works. I also cant see where this is set fdtfile=imx8mp-evk-dsp.dtb

[Sanket_Parekh]

Hi @LBr ,

I hope you are doing well.

I couldn't find any reference in the uboot source code that sets default fdtfile as imx8mp-evk-dsp.dtb.

Please share  .config file generated after the u-boot build.

Please make sure that you have correctly replaced the below configuration in uboot defconfg,

CONFIG_DEFAULT_DEVICE_TREE="imx8mp-evk-sof-wm8960"
CONFIG_DEFAULT_FDT_FILE="imx8mp-evk-sof-wm8960.dtb"

Please cross-check that any custom yocto patch is not overriding this configuration.

One could try running search for imx8mp-evk-dsp.dtb keyword in u-boot and yocto source code.

Thanks & Regards,

Sanket Parekh

[LBr]

I searched for both multiple times. And I'm using the default distro from NXP, no patches of our own.

[Sanket_Parekh]

Hi @LBr ,

I hope you are doing well.

Please make sure that changes made to the u-boot configuration appear in the final build.

Please provide .config in u-boot build dir.

Please make sure that machine.conf contains the correct device tree.

NXP BSP by default use imx8mp-evk.dts.

One could try using a pre-built image in  i.MX 8M Plus EVK.

Please provide me with MACHINE_NAME, machine.conf, and the steps used to build an image for further debugging.

Thanks & Regards,

Sanket Parekh

[LBr]

Hi Sanket:
Please do the following:
* Download a fresh yocto Linux 5.15.71_2.2.0 and compile
* you will see it assigns by default "imx8mp-evk-dsp.dtb"
* Try to changeaccording to your previous instrucctions, you will see how it doesnt work

[Sanket_Parekh]

Hi @LBr ,

I hope you are doing well.

Please make sure that you have referred to Chapter 5 - Image Build and selected imx8mp-lpddr4-evk as a MACHINE in local.conf in i.MX Yocto Project User's Guide.

Please try re-building u-boot from scratch.

with the below changes in imx8mp_evk_defconfig by applying the patch.

CONFIG_DEFAULT_DEVICE_TREE="imx8mp-evk-sof-wm8960"
CONFIG_DEFAULT_FDT_FILE="imx8mp-evk-sof-wm8960.dtb"

Please do not make any changes related to fdtfile in imx8mp_evk.h 

Please share  .config file generated after the u-boot build.

Thanks & Regards,

Sanket Parekh