FAILED: patch "[PATCH] drm/i915: make compact dma scatter lists creation work with" failed to apply to 3.10-stable tree

[Konrad Rzeszutek Wilk]

On Tue, Jul 23, 2013 at 09:54:57AM -0700, gregkh at linuxfoundation.org wrote:
> 
> The patch below does not apply to the 3.10-stable tree.

You can drop it. The patch is already in 3.10 and it does not need to
be backported to earlier trees.

There was a snaffu were I thought David would post this in v3.11 merge
window - hence the stable at vger.kernel.org tag. But David came in to
rescue me and at the last minute sent an git pull to Linus for v3.10.

So all good.

Thanks!
> If someone wants it applied there, or to any other stable or longterm
> tree, then please email the backport, including the original git commit
> id to <stable at vger.kernel.org>.
> 
> thanks,
> 
> greg k-h
> 
> ------------------ original commit in Linus's tree ------------------
> 
> >From 1625e7e549c50fb57a1e1ab1cb0f5735c84c9029 Mon Sep 17 00:00:00 2001
> From: Konrad Rzeszutek Wilk <konrad.wilk at oracle.com>
> Date: Mon, 24 Jun 2013 11:47:48 -0400
> Subject: [PATCH] drm/i915: make compact dma scatter lists creation work with
>  SWIOTLB backend.
> 
> Git commit 90797e6d1ec0dfde6ba62a48b9ee3803887d6ed4
> ("drm/i915: create compact dma scatter lists for gem objects") makes
> certain assumptions about the under laying DMA API that are not always
> correct.
> 
> On a ThinkPad X230 with an Intel HD 4000 with Xen during the bootup
> I see:
> 
> [drm:intel_pipe_set_base] *ERROR* pin & fence failed
> [drm:intel_crtc_set_config] *ERROR* failed to set mode on [CRTC:3], err = -28
> 
> Bit of debugging traced it down to dma_map_sg failing (in
> i915_gem_gtt_prepare_object) as some of the SG entries were huge (3MB).
> 
> That unfortunately are sizes that the SWIOTLB is incapable of handling -
> the maximum it can handle is a an entry of 512KB of virtual contiguous
> memory for its bounce buffer. (See IO_TLB_SEGSIZE).
> 
> Previous to the above mention git commit the SG entries were of 4KB, and
> the code introduced by above git commit squashed the CPU contiguous PFNs
> in one big virtual address provided to DMA API.
> 
> This patch is a simple semi-revert - were we emulate the old behavior
> if we detect that SWIOTLB is online. If it is not online then we continue
> on with the new compact scatter gather mechanism.
> 
> An alternative solution would be for the the '.get_pages' and the
> i915_gem_gtt_prepare_object to retry with smaller max gap of the
> amount of PFNs that can be combined together - but with this issue
> discovered during rc7 that might be too risky.
> 
> Reported-and-Tested-by: Konrad Rzeszutek Wilk <konrad.wilk at oracle.com>
> CC: Chris Wilson <chris at chris-wilson.co.uk>
> CC: Imre Deak <imre.deak at intel.com>
> CC: Daniel Vetter <daniel.vetter at ffwll.ch>
> CC: David Airlie <airlied at linux.ie>
> CC: <dri-devel at lists.freedesktop.org>
> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk at oracle.com>
> Cc: stable at vger.kernel.org
> Signed-off-by: Daniel Vetter <daniel.vetter at ffwll.ch>
> 
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index a6178bac..e31eeb1d 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -1802,7 +1802,14 @@ i915_gem_object_get_pages_gtt(struct drm_i915_gem_object *obj)
>  			gfp |= __GFP_NORETRY | __GFP_NOWARN | __GFP_NO_KSWAPD;
>  			gfp &= ~(__GFP_IO | __GFP_WAIT);
>  		}
> -
> +#ifdef CONFIG_SWIOTLB
> +		if (swiotlb_nr_tbl()) {
> +			st->nents++;
> +			sg_set_page(sg, page, PAGE_SIZE, 0);
> +			sg = sg_next(sg);
> +			continue;
> +		}
> +#endif
>  		if (!i || page_to_pfn(page) != last_pfn + 1) {
>  			if (i)
>  				sg = sg_next(sg);
> @@ -1813,8 +1820,10 @@ i915_gem_object_get_pages_gtt(struct drm_i915_gem_object *obj)
>  		}
>  		last_pfn = page_to_pfn(page);
>  	}
> -
> -	sg_mark_end(sg);
> +#ifdef CONFIG_SWIOTLB
> +	if (!swiotlb_nr_tbl())
> +#endif
> +		sg_mark_end(sg);
>  	obj->pages = st;
>  
>  	if (i915_gem_object_needs_bit17_swizzle(obj))
>