lib: Preallocate framebuffers

So for reasons unfathomable CRC appear to be miscalculated when the
plane is not in the mappable aperture. Worrisome, but for now
preallocate space in the mappable region for the new framebuffer and
design some specific tests to explore the issue further.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

1 files changed, 6 insertions, 0 deletions

diff --git a/lib/igt_fb.c b/lib/igt_fb.c
index 61205f34..47472f43 100644
--- a/lib/igt_fb.c
+++ b/lib/igt_fb.c
@@ -203,10 +203,16 @@ static int create_bo_for_fb(int fd, int width, int height, uint32_t format,
 			*is_dumb = false;
 
 		if (is_i915_device(fd)) {
+			uint32_t *ptr;
 
 			bo = gem_create(fd, size);
 			gem_set_tiling(fd, bo, tiling, stride);
 
+			/* Ensure the framebuffer is preallocated */
+			ptr = gem_mmap__gtt(fd, bo, size, PROT_READ);
+			igt_assert(*ptr == 0);
+			munmap(ptr, size);
+
 			if (size_ret)
 				*size_ret = size;