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Date:	Mon, 28 Jul 2014 13:20:58 +0200
From:	Pavel Machek <>
Subject: [PATCH] work around warning in i915_gem_gtt

Gcc warns that addr might be used uninitialized. It may not, but I see
why gcc gets confused.

Additionally, hiding code with side-effects inside WARN_ON() argument
seems uncool, so I moved it outside.

Signed-off-by: Pavel Machek <>

diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c
index 8b3cde7..8fcc974 100644
--- a/drivers/gpu/drm/i915/i915_gem_gtt.c
+++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
@@ -1448,7 +1448,7 @@ static void gen6_ggtt_insert_entries(struct i915_address_space *vm,
 		(gen6_gtt_pte_t __iomem *)dev_priv->gtt.gsm + first_entry;
 	int i = 0;
 	struct sg_page_iter sg_iter;
-	dma_addr_t addr;
+	dma_addr_t addr = 0;
 	for_each_sg_page(st->sgl, &sg_iter, st->nents, 0) {
 		addr = sg_page_iter_dma_address(&sg_iter);
@@ -1462,9 +1462,10 @@ static void gen6_ggtt_insert_entries(struct i915_address_space *vm,
 	 * of NUMA access patterns. Therefore, even with the way we assume
 	 * hardware should work, we must keep this posting read for paranoia.
-	if (i != 0)
-		WARN_ON(readl(&gtt_entries[i-1]) !=
-			vm->pte_encode(addr, level, true));
+	if (i != 0) {
+		unsigned long gtt = readl(&gtt_entries[i-1]);
+		WARN_ON(gtt != vm->pte_encode(addr, level, true));
+	}
 	/* This next bit makes the above posting read even more important. We
 	 * want to flush the TLBs only after we're certain all the PTE updates

(cesky, pictures)
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