Re: [microblaze-uclinux] Fwd: uClinux over microblaze --- Simulation

[John Williams <jwilliams@xxxxxxxxxxxxxx>]

Hi Sashti,

sashti srinivasan wrote:
>    Thanks to the microblaze uCLinux home page, I
>  obtained the toolchain and uclinux sources from
> uclinux.org.  I built the uclinux and image.elf is
> created.

That's a good start!

>      Now I want to run this image.elf in an
>  instruction  set simulator. 

Unfortunately, I don't think this is currently possible.  I hoped to do 
this when initially porting the kernel, but several things got in the 
way - see below.

> Please guide me
> regarding wherefrom this can be obtained.  I have
> installed the xilinx edk, but could not find the
> instruction set simulator
>  in that.  The simulator iss.exe is only for powerpc.

The microblaze instruction set simulator is built into the XMD 
application.  To do ISS for microblaze, you start XMD, and execute the 
command "mbconnect sim" to start the simulator.  You then start gdb and 
connect a remote session to the ISS (XMD).  There may also be a 
microblaze ISS built into mb-gdb, but I'm not sure.

But...

(1) For some reason the ISS only supports a maximum memory size of 
64Kbyte.  Since XMD is closed source, xilinx would have to change this, 
or you would have to write/modify your own ISS.

(2) the ISS doesn't simulate any hardware functionality or peripherals. 
  So, no interrupts, no timers, no I/O, nothing.  Even if you could step 
the kernel through the ISS, timer interrupts would never occur, no 
devices would be simulated, and so on.

If there is an ISS in mb-gdb you could potentially extend the simulation 
model to simulate the interrupt controller, and some simple peripherals 
and so on, but it will not be trivial.

Of course, you could do a behavioural logic simulation of an entire 
microblaze system, at RTL level, but your effective clock rate would be 
measured in microHertz!  The uClinux kernel would take about 3 weeks to 
boot!

If I've overlooked something I'd love to hear about it - software 
simulation of microblaze systems would be a rgeat prototyping 
tool/capability.

Cheers,

John

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