work around warning in i915_gem_gtt
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Message ID 20140728112058.GA17504@amd.pavel.ucw.cz
State New, archived
Headers show

Commit Message

Pavel Machek July 28, 2014, 11:20 a.m. UTC
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 <pavel@ucw.cz>

Comments

Daniel Vetter July 28, 2014, 3:24 p.m. UTC | #1
On Mon, Jul 28, 2014 at 01:20:58PM +0200, Pavel Machek wrote:
> 
> 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 <pavel@ucw.cz>
> 
> 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;

I want to have a /* shuts up gcc */ for these kinds of things, where we
need to help out the compiler. Added and merged, thanks.
-Daniel

>  
>  	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
> 
> -- 
> (english) http://www.livejournal.com/~pavelmachek
> (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/dri-devel

Patch
diff mbox

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