lib: Add function to hash a framebuffer

To use writeback buffers as a CRC source, we need to be able to hash
them. Implement a simple FVA-1a hashing routine for this purpose.

Doing a bytewise hash on the framebuffer directly can be very slow if
the memory is noncached. By making a copy of each line in the FB first
(which can take advantage of word-access speedup), we can do the hash
on a cached copy, which is much faster (10x speedup on my platform).

Changes since V7 (Maxime Ripard):
* Maxime Ripard:
  - Replace `gem_mmap__gtt` by `igt_fb_map_buffer` on `igt_fb_get_crc()`
* Rodrigo Siqueira:
  - Rename igt_fb_get_crc to igt_fb_get_fnv1a_crc

Changes since V6 (Simon Ser):
* Use plain uint32_t for FNV1a_OFFSET_BIAS and FNV1a_PRIME
* Return -EINVAL in case fb->num_planes != 1
* Just copy fb->width * cpp instead of copy the whole stride

v5: use igt_memcpy_from_wc() instead of plain memcpy, as suggested by
    Chris Wilson

Signed-off-by: Brian Starkey <brian.starkey@arm.com>
[rebased and updated to the most recent API]
Signed-off-by: Liviu Dudau <liviu.dudau@arm.com>
[rebased and updated]
Signed-off-by: Rodrigo Siqueira <rodrigosiqueiramelo@gmail.com>
Reviewed-by: Simon Ser <simon.ser@intel.com>
Reviewed-by: Liviu Dudau <liviu.dudau@arm.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/lib/igt_fb.h b/lib/igt_fb.h
index 5ec906b7..debfb5ad 100644
--- a/lib/igt_fb.h
+++ b/lib/igt_fb.h
@@ -207,5 +207,7 @@ int igt_format_plane_bpp(uint32_t drm_format, int plane);
 void igt_format_array_fill(uint32_t **formats_array, unsigned int *count,
 			   bool allow_yuv);
 
+int igt_fb_get_fnv1a_crc(struct igt_fb *fb, igt_crc_t *crc);
+
 #endif /* __IGT_FB_H__ */