Problem with MPC823 LCD driver

Problem with MPC823 LCD driver

[Kim Jørgensen]

Hi.

I got a custom MPC823E board, and I want to use a LCD display with Linux.
So I removed the HIOX specific line in lcd823.c, and added the LCD frame
buffer to the kernel. But I got a problem; the kernel crashes about 3
seconds after bash gets started, with this message:

init-2.00# Kernel panic: Kernel Mode Software FPU Emulation
Kernel panic: Kernel Mode Software FPU Emulation
Kernel panic: Kernel Mode Software FPU Emulation
Kernel panic: Kernel Mode Software FPU Emulation
Kernel panic: Kernel Mode Software FPU Emulation
Kernel panic: Kernel Mode Software FPU Emulation
Kernel panic: Kernel Mode Software FPU Emulation
Kernel panic: Kernel Mode Software FPU Emulation
Kernel panic: Kernel Mode Software FPU Emulation
Kernel panic: Kernel Mode Software FPU Emulation
Kernel panic: Kernel Mode Software FPU Emulation
Kernel stack overflow in process c02f8000, r1=c02f82d0
NIP: C0054D20 XER: 8000BC7F LR: C0054D20 REGS: c02f8220 TRAP: 1000
MSR: 00001032 EE: 0 PR: 0 FP: 0 ME: 1 IR/DR: 11
Machine check in kernel mode.
Caused by (from msr): regs c006ff00 Machine check signal - probably due to
mm fault
with mmu off
NIP: 00001230 XER: A000BC7F LR: C0002544 REGS: c006ff00 TRAP: 0200
MSR: 00001000 EE: 0 PR: 0 FP: 0 ME: 1 IR/DR: 00
Machine check in kernel mode.
Caused by (from msr):

Can anyone tell me what is wrong, and how to solve this?

I'm using the kernel from mvista and I have enabled Math Emulation. The
kernel runs fine without the LCD driver.
I have used the LCD driver on a PRXL board without any problems.

---
Kim Jorgensen


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Re: Problem with MPC823 LCD driver

[Dan Malek]

Kim Jørgensen wrote:

> I got a custom MPC823E board, and I want to use a LCD display with Linux.

Get the logic analyzer on the bus.......

> Can anyone tell me what is wrong, and how to solve this?

I can make a few guesses.  This has nothing to do with Math Emulation,
and everything to do with fetching the proper instructions into the
core.  The LCD controller is a heavy-duty DMA controller that has
priority over everything to ensure it can keep the display updated
from system memory.  Since the controller performs large burst mode
operations, this is a classic example of memory controller or memory
interface problems.  I suspect the memory timing isn't correct and the
instructions are just bad memory cycles that can't be properly
decoded.


	-- Dan

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Re: Problem with MPC823 LCD driver

[Richard Hendricks]

That could be it.  One obvious indicator is that without LCD and
the caches disabled, everything works fine.  If it breaks with the
caches turned on, check your UPM burst tables.  This is where most
mistakes occur.  Also, be sure to bring all the UPM signals back
high at the end of your transactions.

Dan Malek wrote:
>
> Kim Jørgensen wrote:
>
> > I got a custom MPC823E board, and I want to use a LCD display with Linux.
>
> Get the logic analyzer on the bus.......
>
> > Can anyone tell me what is wrong, and how to solve this?
>
> I can make a few guesses.  This has nothing to do with Math Emulation,
> and everything to do with fetching the proper instructions into the
> core.  The LCD controller is a heavy-duty DMA controller that has
> priority over everything to ensure it can keep the display updated
> from system memory.  Since the controller performs large burst mode
> operations, this is a classic example of memory controller or memory
> interface problems.  I suspect the memory timing isn't correct and the
> instructions are just bad memory cycles that can't be properly
> decoded.
>
>         -- Dan
>

--
MPC823 Applications Engineering Development

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