[Intel-gfx] [PATCH] drm/i915: Round tile chunks up for constructing partial VMAs

[Chris Wilson]

When we split a large object up into chunks for GTT faulting (because we
can't fit the whole object into the aperture) we have to align our cuts
with the fence registers. Each partial VMA must cover a complete set of
tile rows or the offset into each partial VMA is not aligned with the
whole image. Currently we enforce a minimum size on each partial VMA,
but this minimum size itself was not aligned to the tile row causing
distortion.

Reported-by: Andreas Reis <andreas.reis at gmail.com>
Reported-by: Chris Clayton <chris2553 at googlemail.com>
Reported-by: Norbert Preining <preining at logic.at>
Tested-by: Norbert Preining <preining at logic.at>
Fixes: 03af84fe7f48 ("drm/i915: Choose partial chunksize based on tile row size")
Fixes: a61007a83a46 ("drm/i915: Fix partial GGTT faulting") # enabling patch
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=98402
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
Cc: Jani Nikula <jani.nikula at linux.intel.com>
Cc: <drm-intel-fixes at lists.freedesktop.org> # v4.9-rc1+
---
 drivers/gpu/drm/i915/i915_gem.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index c642385bb236..a52b40bbac6f 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -1837,7 +1837,7 @@ int i915_gem_fault(struct vm_area_struct *area, struct vm_fault *vmf)
 		/* Use a partial view if it is bigger than available space */
 		chunk_size = MIN_CHUNK_PAGES;
 		if (i915_gem_object_is_tiled(obj))
-			chunk_size = max(chunk_size, tile_row_pages(obj));
+			chunk_size = roundup(chunk_size, tile_row_pages(obj));
 
 		memset(&view, 0, sizeof(view));
 		view.type = I915_GGTT_VIEW_PARTIAL;
-- 
2.10.2