[xtensa] support multiple config using the same xt-sim board

[williamtcdns]

When using Xtensa tools the environment variable XTENSA_CORE must be set to the config to use.

Currently the board xt-sim is hardwired to use sample_controller, and XTENSA_CORE must be set to sample_controller.

I would like to support the config hifi5s_ao_7 using the board xt-sim.
I implemented the support and successfully built and ran samples/hello_world in the following commit:
williamtcdns@db88e999ed6
However, in doing so, I have to replace the hardwired use of sample_controller by hifi5s_ao_7 by editing 3 files:

• boards/cdns/xt-sim/Kconfig.xt-sim
• boards/cdns/xt-sim/board.yml
• boards/cdns/xt-sim/xt-sim.dts

Is it possible to have above 3 edited files automatically select between sample_controller and hifi5s_ao_7 based on the value of the environment variable XTENSA_CORE ?

[williamtcdns]

@henrikbrixandersen @dcpleung @andyross @nashif @ceolin

[williamtcdns]

Please note that config hifi5s_ao_7 is available in Xtensa tools RJ-2024.3 .

[dcpleung]

xt-sim is a simulator and is not a board. If you need to support a new SoC, you need to create a new SoC configuration and corresponding board configuration. In the board configuration, you can specify that you want to use xt-sim as the simulator.

[williamtcdns]

Yes xt-sim is a simulator, but there is a board by the same name implemented at boards/cdns/xt-sim such that it can be used as follow west build -b xt-sim samples/hello_world .

In the commit williamtcdns@db88e999ed6 , I did create a new SoC configuration under soc/cdns/hifi5s_ao_7 and specified it in the xt-sim board configuration, but in doing so, I have to replace the xtensa_sample_controller SoC currently specified in the xt-sim board configuration.

My request for help is whether it is possible to have a board support multiple SoC.

[williamtcdns]

It seems to be possible when I look at boards/digilent/arty_a7/Kconfig.arty_a7 which selects between 2 SoCs.

In my case, for boards/cdns/xt-sim, I would like to select between the SoCs xtensa_sample_controller and hifi5s_ao_7 based on the value of the environment variable XTENSA_CORE.

If possible, could you provide an outline of the files to use or changes to make ?

[dcpleung]

Maybe you can follow the arty_a7 board and see what changes you can make to enable your usage?

[andyross]

We don't really have a clean answer here. The metaphor is that boards/soc/arch is fixed hierarchically. Strictly you'd want a separate board variant defined for every XTENSA_CORE, which is exactly what you don't want.

This is unlikely to work without surgery. Note that the DTS is downstream of kconfig, so it would be possible to define e.g. a "ARCH_XTENSA_CORE_ID" variable which you'd then select on in the dts, which can reduce some boilerplate. Then if you wanted to use the $XTENSA_CORE variable in the environment, you'd need to extract it in the cmake somewhere and set it in kconfig.

Mostly it just requries some thought and design, I suspect. I'm not the hardware model expert, really.