[LITMUS^RT] Litmus on single-board computer

[Martinez Garcia Jorge Luis (PS-EC/ESB2)]

Hello Björn, 
I managed to successfully get LITMUS^RT on top of a vanilla kernel on the RPi 3 more or less as you suggested (I will publish exactly what I did in a following email). 
By adding the LITMUS^RT patches on top of the vanilla kernel and compiling, I am only building a LITMUS^RT kernel. Now, do I need to consider something else apart from what is written in the documentation (https://www.litmus-rt.org/installation.html), in order to build liblitmus and the Feather-Trace Tools for the RPi 3?
Regards, 
Jorge

-----Original Message-----
From: litmus-dev [mailto:litmus-dev-bounces at lists.litmus-rt.org] On Behalf Of Björn Brandenburg
Sent: Montag, 18. Dezember 2017 17:21
To: litmus-dev at lists.litmus-rt.org
Subject: Re: [LITMUS^RT] Litmus on single-board computer

On 14. Dec 2017, at 19:22, Martinez Garcia Jorge Luis (DGS-EC/ESB2) <JorgeLuis.MartinezGarcia at de.bosch.com> wrote:
> 
> 
> # I copied your .config file and set "CONFIG_MODULES=y" since it is needed to make "modules_install" later on.
> $ make ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- -j4 

Presumably you need other config options as well, not just CONFIG_MODULES, to make the kernel work with your distribution. 

> 
> Now, when I reboot the RPi 3, it gets stuck on the rainbow screen.

I’m not quite sure what you mean by “rainbow screen”. Is this the boot splash screen? I exclusively use the RPi via the serial port, so I’m not sure what you are referring to.

If this is the boot splash screen, you need to figure out why the boot is stalling. Perhaps a missing file system driver? Something else missing? It’s most likely some mismatch between the distribution’s user land and the features built into the kernel. 

If the kernel stalls during boot, then there should be some informative error messages, unless it is truly locking up. If you cannot get to the messages via the graphical console, try connecting via the serial port and make sure the kernel emits the system console vial the serial port. 

> Do I have to compress the kernel image

No, the kernel’s Makefile does this for you if you are building compressed kernel. 

> or did I miss something? 

Unless you are using the same distribution, my config is likely not going to work without further modifications. I would suggest to first boot with the distribution kernel of the distribution that you are using, and to then build a local reference config using  'make localmodconfig’ or ‘make localyesconfig’ (I used the latter to arrive at my kernel config).

In particular, before trying to boot a kernel with the LITMUS^RT patches applied, just try to get a regular self-compiled Linux kernel working on the board. The issues that you are currently facing are not related to LITMUS^RT, so it would be best to focus on figuring out how to boot a vanilla Linux kernel first, before adding the complexities of non-mainline patches. 

- Björn


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