mmap + segfaults on MPC8349E

R. Ebersole (VTI - new) rje at
Tue Dec 11 12:53:10 EST 2007

David Hawkins wrote:

> Hi,


> You haven't really provided enough information.

Sorry about that.  I grabbed one of the h/w guys to help out.

>> We wrote some simple drivers/modules to mmap() FPGA registers to user 
>> space.
>> At the moment, for testing, we reserve the upper x-MB of RAM, and 
>> mmap() there, instead.
> 1. The FPGA is located where? The local bus, or the PCI bus?
>    What frequency are you trying to operate at? 

On the local bus frequency is 33.0 MHz. (66.0 PCI_CLK_IN).  See the 
attached .cfg script for memory map.

> 2. If its on the local bus, do you access it using GPCM or UPM?
>    Have you setup either correctly?
>    Have you confirmed the bus timing with a logic analyzer? 

We have confirmed the timing both in functionality (in the debugger) and 
with a logic analyzer (plus oscope for setup and hold times).
We have stand-alone C-code that runs in CodeWarrior that bangs away at 
the registers of this device and the hardware runs perfectly using the 
.cfg script settings..

> 3. Have you created a bus functional model of the processor bus
>    that you have then run with your FPGA bus in ModelSim to
>    confirm that your FPGA performs correctly. 

Yes, we have.  Also, checked in h/w (see 2 above)

> 4. Have you tried burst and non-burst access by either using
>    DMA, or treating the memory area as cacheable or non-cacheable?
>    Have you checked those cases with simulation and then
>    with a scope or logic analyzer?

Always non-burst at this point.

> 5. Did you try running stand-alone tests in U-Boot, to go for a
>    more bare-metal debug approach?

I assume the bare-metal debug approach is using a JTAG debugger 
connection and CodeWarrior.  We started there and now are trying to 
access the same device(s) via linux drivers.

> No point in debugging software if you have no idea whether the
> hardware behaves. So confirm that you have tested your hardware
> first.
> My board design uses the MPC8349EA, I have an Altera Stratix II
> FPGA on the local bus. I use GPCM to access flash on the local
> bus via the FPGA, and UPM to access FPGA registers. I don't
> have boards yet, but I've got a pretty good handle on how the
> interface should work.
> Cheers,
> Dave


Sometimes I feel like a red shirt in the Star Trek episode of life.


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