linux-kernel - Re: [BUG/RFC/PATCH] drm: Fix for non-coherent DMA PowerPC

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Date:	Mon, 03 Mar 2008 20:51:17 +0100
From:	"Gerhard Pircher" <gerhard_pircher@....net>
To:	benh@...nel.crashing.org
Cc:	airlied@...ux.ie, linux-kernel@...r.kernel.org,
	dri-devel@...ts.sourceforge.net, linuxppc-dev@...abs.org
Subject: Re: [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@...nel.crashing.org>
> An: Gerhard Pircher <gerhard_pircher@....net>
> CC: linuxppc-dev@...abs.org, dri-devel@...ts.sourceforge.net, linux-kernel@...r.kernel.org, airlied@...ux.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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