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    SubjectRe: [BUG/RFC/PATCH] drm: Fix for non-coherent DMA PowerPC

    -------- Original-Nachricht --------
    > Datum: Mon, 03 Mar 2008 09:56:09 +1100
    > Von: Benjamin Herrenschmidt <benh@kernel.crashing.org>
    > An: Gerhard Pircher <gerhard_pircher@gmx.net>
    > CC: linuxppc-dev@ozlabs.org, dri-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org, airlied@linux.ie
    > Betreff: Re: [BUG/RFC/PATCH] drm: Fix for non-coherent DMA PowerPC

    > Bah, I think I found the problem:
    >
    > +static inline void *drm_vmalloc_dma(unsigned long size)
    > +{
    > +#if defined(__powerpc__) && defined(CONFIG_NOT_COHERENT_CACHE)
    > + return __vmalloc(size, GFP_KERNEL | __GFP_HIGHMEM,
    > + PAGE_KERNEL | _PAGE_NO_CACHE);
    > +#else
    > + return vmalloc_32(size);
    > +#endif
    > +}
    > +
    >
    > Remove the GFP_HIGHMEM from the above. It looks like our cache
    > flushing isn't going to work for highmem, it would need some
    > kmap's for that.
    Yes, it looks like this was the problem. No kernel oops anymore.
    The machine locks up anyway (which is a well known hardware problem).
    It doesn't lock up with CPPIOMode=true, but probably only because the
    initialization of DRI fails with "BAD cp_mode (f0000000)!".

    Gerhard
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