Re: [Qemu-discuss] Custom board with DTS/DTB

[Thomas Huth]

On 17.11.2016 23:14, James Hanley wrote:
> I saw the presentation on “Custom Hardware Modeling for FPGAs and
> Embedded Linux Platforms with QEMU” via
> http://free-electrons.com/pub/video/2010/elc/elc2010-williams-iglesias-fpga-qemu.ogv
> and was trying to apply the concepts described against our custom board
> design, and defining the board using dts.  I haven't been able to really
> get far and was looking for some guidance if this is the right direction.
> The mcu is a cortex-m4 (Atmel)
> The target firmware is running an RTOS (not Linux)
> 
> QEMU emulator version 2.7.50 (v2.7.0-1890-g83c83f9-dirty)
> Copyright (c) 2003-2016 Fabrice Bellard and the QEMU Project developers
> 
> It's my understanding that the dtb option passes a file that includes
> details of the machine that qemu can use to map out peripherals for it
> without having to compile the machine into qemu - is this a
> misunderstanding?

As far as I know, the -dtb parameter only passes the device tree blob to
the kernel image. I think QEMU does not look at the contents of that file.
So you've got to instantiate the corresponding devices manually with the
"-device" parameter of QEMU. Simply run QEMU with "-device ?" for a list
of supported devices.
However, I'm not familiar with ARM machines of QEMU, not sure whether
you can successfully populate a "none" machine that way. So you rather
might need to modify the source code by copying one of the existing
boards and adapting it to your needs.

> When I attempt to connect to qemu from gdb the qemu instance segfaults.

That should not happen. Can you get a backtrace to see where this happened?

 Thomas