Subject: Re: Disabling L1 D-cache and side effects

From: Olof Johansson <[email-masked]>
Date: Mon, 29 Sep 2008 13:04:55 -0500

On Mon, Sep 29, 2008 at 10:05:41AM -0700, Tirumala Reddy Marri wrote:
>  
> Hi,
>   I had to bring up a PPC based SOC with L1 dcache disabled.  I did that
> and tried to boot Linux using RAMDISK/NFS mount. In RAMDISK I see the
> file system errors. In case of NFS mount I see error saying failed to
> load ld.so library.
>  
>  Could you guys please share thoughts what are the different side
> effects might be causing this.

There are a number of things you have to be careful about when you
disable caches. Depending on your implementation, you likely can't use
lwarx/stwcx, cache ops will not work, etc. Also, are you 100% sure that
this is caused only by disabling L1D, and not by any other problems with
your silicon?

If you're doing early bringup of you'll have a whole lot of debug work
in front of you, and this mailing list is probably not the best place
to bring your homework.

-Olof