[PATCH 1/4] drm/i915: Avoid div-by-zero on gen2

[PATCH 1/4] drm/i915: Avoid div-by-zero on gen2

[Ville Syrjala]

From: Ville Syrjälä <ville.syrjala@linux.intel.com>

Gen2 tiles are 2KiB in size so i915_gem_object_get_tile_row_size()
can in fact return <4KiB, which leads to div-by-zero here.
Avoid that.

Not sure i915_gem_object_get_tile_row_size() is entirely
sane anyway since it doesn't account for the different tile
layouts on i8xx/i915...

I'm not able to hit this before commit 6846895fde05 ("drm/i915:
Replace PIN_NONFAULT with calls to PIN_NOEVICT") and it looks
like I also need to run recent version of Mesa. With those in
place xonotic trips on this quite easily on my 85x.

Cc: stable@vger.kernel.org
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
---
 drivers/gpu/drm/i915/gem/i915_gem_mman.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_mman.c b/drivers/gpu/drm/i915/gem/i915_gem_mman.c
index 2561a2f1e54f..8598a1c78a4c 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_mman.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_mman.c
@@ -189,7 +189,7 @@ compute_partial_view(const struct drm_i915_gem_object *obj,
 	struct i915_ggtt_view view;
 
 	if (i915_gem_object_is_tiled(obj))
-		chunk = roundup(chunk, tile_row_pages(obj));
+		chunk = roundup(chunk, tile_row_pages(obj) ?: 1);
 
 	view.type = I915_GGTT_VIEW_PARTIAL;
 	view.partial.offset = rounddown(page_offset, chunk);
-- 
2.26.3