[PATCH] drm: modify pages_to_sg prime helper to create optimized SG table

[Daniel Vetter]

On Tue, Jan 29, 2013 at 09:10:40AM -0800, Aaron Plattner wrote:
> On 01/28/2013 05:38 AM, Rahul Sharma wrote:
> >It fixes the issue arises due to passing 'nr_pages' in place of 'nents' to
> >sg_alloc_table. When ARM_HAS_SG_CHAIN is disabled, it is causing failure in
> >creating SG table for the buffers having more than 204 physical pages i.e.
> >equal to SG_MAX_SINGLE_ALLOC.
> >
> >When using sg_alloc_table_from_pages interface, in place of sg_alloc_table,
> >page list will be passes to get each contiguous section which is represented
> >by a single entry in the table. For a Contiguous Buffer, number of entries
> >should be equal to 1.
> >
> >Following check is causing the failure which is not applicable for Non-Contig
> >buffers:
> >
> >	if (WARN_ON_ONCE(nents > max_ents))
> >		return -EINVAL;
> >
> >Above patch is well tested for EXYNOS4 and EXYNOS5 for with/wihtout IOMMU
> >supprot. NOUVEAU and RADEON platforms also depends on drm_prime_pages_to_sg
> >helper function.
> >
> >This set is base on "exynos-drm-fixes" branch at
> >http://git.kernel.org/?p=linux/kernel/git/daeinki/drm-exynos.git
> >
> >Signed-off-by: Rahul Sharma <rahul.sharma at samsung.com>
> 
> Reviewed-by: Aaron Plattner <aplattner at nvidia.com>
> 
> I also verified that this reduces my 2025-entry sg_table to 6 entries, so
> 
> Tested-by: Aaron Plattner <aplattner at nvidia.com>

I've just merged the drm/i915 fixes and this patch on top to
drm-intel-next-queued. I'll send the pull request to Dave somewhen next
week, presuming nothing unexpected blows up. Thanks for the patch&review.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch