Linux Kernel Issue: MPC8540 Errata (CPU29)

[Chiradeep Vittal]

It turns out to be a compiler issue.
We're using gcc 3.4.3 with optimization level -Os. The following program will generate the illegal instruction with -Os but not with -O2
	int main (int argc, char** argv)
	{	
	  int seq[] = {0, 1, 2};
	  return 0;
	}
The reason is that the compiler generates code with the stswi instruction which is not supported by the e500. Here's our compiler configuration:
Configured with: /home/steve/perforce/sw/opt/crosstool/build/powerpc-8540-linux-gnu/gcc-3.4.3-glibc-2.3.2/gcc-3.4.3/configure --target=powerpc-8540-linux-gnu --host=i686-host_pc-linux-gnu --prefix=/home/steve/perforce/sw/opt/cross-compile/powerpc-8540-linux-gnu/gcc-3.4.3-glibc-2.3.2 --with-cpu=8540 --enable-cxx-flags=-mcpu=8540 --with-headers=/home/steve/perforce/sw/opt/cross-compile/powerpc-8540-linux-gnu/gcc-3.4.3-glibc-2.3.2/powerpc-8540-linux-gnu/include --with-local-prefix=/home/steve/perforce/sw/opt/cross-compile/powerpc-8540-linux-gnu/gcc-3.4.3-glibc-2.3.2/powerpc-8540-linux-gnu --disable-nls --enable-threads=posix --enable-symvers=gnu --enable-__cxa_atexit --enable-languages=c,c++ --enable-shared --enable-c99 --enable-long-long

Any recommendations?

Thanks
--
Chiradeep

-----Original Message-----
From: Kumar Gala [mailto:kumar.gala at freescale.com] 
Sent: Wednesday, April 27, 2005 11:37 AM
To: Chiradeep Vittal
Cc: linuxppc-embedded at ozlabs.org
Subject: Re: Linux Kernel Issue: MPC8540 Errata (CPU29)

On Apr 27, 2005, at 12:46 PM, Chiradeep Vittal wrote:

> We're running Linux Kernel 2.4.26 on an 8540 ADS derivative. We're
>  seeing an
> "illegal instruction"  (SIGILL) exception under some circumstances
> (during a pthread_create call). We were wondering if this could be a
> symptom of
> CPU29 and if there is a patch available for CPU29.
>
> "CPU29 L1 instruction cache gets multiple entries for same line after
>  change
> in MSR[IS] bit "
>
> www.freescale.com/files/32bit/doc/errata/MPC8540CE.pdf

The way the Linux kernel manages the MMU on e500 it doesn't actually 
ever modify MSR[IS] or MSR[DS].  They are always zero so I dont believe 
you are hitting this errata.

Are you running with math emulation turned on?  Do you know what the 
instruction is that causes the SIGILL?

- kumar