Re: [PATCH igt 00/10] igt_fb buffer sizes + kms_frontbuffer_tracking

[Daniel Vetter <daniel@ffwll.ch>]

On Fri, Nov 13, 2015 at 03:12:41PM -0200, Paulo Zanoni wrote:
> Hello
> 
> I've been carrying some local IGT patches that reduced the size of buffers
> created by igt_create_fb() so they would fit the stolen memory, but when I
> decided to test the tree without them, I concluded the lack of sane sizes was
> even causing test failures. So here's my attempt to fix this. This series alone
> should help reducing the number of kms_frontbuffer_tracking failures seen by QA.
> 
> The last few patches make the FBC tests a little harder. They are all based on
> the feedback I got from the last patches I sent.

The point of a helper library is that it helps, not that every caller has
to work around it's choice of size and stride.

The only thing we need to do here is fix up the selection of stride and
size to make it not pick the super-conservative value that work even on
gen2&3. Something like:

diff --git a/lib/igt_fb.c b/lib/igt_fb.c
index 13a6a34982e0..9eb97952ed95 100644
--- a/lib/igt_fb.c
+++ b/lib/igt_fb.c
@@ -87,21 +87,26 @@ static int create_bo_for_fb(int fd, int width, int height, int bpp,
 	if (tiling != LOCAL_DRM_FORMAT_MOD_NONE) {
 		int v;
 
-		/* Round the tiling up to the next power-of-two and the
-		 * region up to the next pot fence size so that this works
-		 * on all generations.
-		 *
-		 * This can still fail if the framebuffer is too large to
-		 * be tiled. But then that failure is expected.
-		 */
-
-		v = width * bpp / 8;
-		for (stride = 512; stride < v; stride *= 2)
-			;
-
-		v = stride * height;
-		for (size = 1024*1024; size < v; size *= 2)
-			;
+		if (gen < 4) {
+			/* Round the tiling up to the next power-of-two and the
+			 * region up to the next pot fence size so that this works
+			 * on all generations.
+			 *
+			 * This can still fail if the framebuffer is too large to
+			 * be tiled. But then that failure is expected.
+			 */
+
+			v = width * bpp / 8;
+			for (stride = 512; stride < v; stride *= 2)
+				;
+
+			v = stride * height;
+			for (size = 1024*1024; size < v; size *= 2)
+				;
+		} else {
+			stride = ALIGN(stride, 512);
+			size = ALIGN(size, stride * 32);
+		}
 	} else {
 		/* Scan-out has a 64 byte alignment restriction */
 		stride = (width * (bpp / 8) + 63) & ~63;


Or whatever is the right thing to pick that works on gen4+.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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