From: Brian Starkey <rodrigosiqueiramelo@xxxxxxxxx>
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@xxxxxxx>
[rebased and updated to the most recent API]
Signed-off-by: Liviu Dudau <liviu.dudau@xxxxxxx>
[rebased and updated]
Signed-off-by: Rodrigo Siqueira <rodrigosiqueiramelo@xxxxxxxxx>
Reviewed-by: Simon Ser <simon.ser@xxxxxxxxx>
Reviewed-by: Liviu Dudau <liviu.dudau@xxxxxxx>
---
lib/igt_fb.c | 63 ++++++++++++++++++++++++++++++++++++++++++++++++++++
lib/igt_fb.h | 2 ++
2 files changed, 65 insertions(+)
diff --git a/lib/igt_fb.c b/lib/igt_fb.c
index 3864b7a1..5e3706e9 100644
--- a/lib/igt_fb.c
+++ b/lib/igt_fb.c
@@ -3783,6 +3783,69 @@ bool igt_fb_supported_format(uint32_t drm_format)
return true;
}
+/*
+ * This implements the FNV-1a hashing algorithm instead of CRC, for
+ * simplicity
+ * http://www.isthe.com/chongo/tech/comp/fnv/index.html
+ *
+ * hash = offset_basis
+ * for each octet_of_data to be hashed
+ * hash = hash xor octet_of_data
+ * hash = hash * FNV_prime
+ * return hash
+ *
+ * 32 bit offset_basis = 2166136261
+ * 32 bit FNV_prime = 224 + 28 + 0x93 = 16777619
+ */
+int igt_fb_get_fnv1a_crc(struct igt_fb *fb, igt_crc_t *crc)
+{
+ const uint32_t FNV1a_OFFSET_BIAS = 2166136261;
+ const uint32_t FNV1a_PRIME = 16777619;
+ uint32_t hash;
+ void *map;
+ char *ptr, *line = NULL;
+ int x, y, cpp = igt_drm_format_to_bpp(fb->drm_format) / 8;
+ uint32_t stride = calc_plane_stride(fb, 0);
+
+ if (fb->num_planes != 1)
+ return -EINVAL;
+
+ ptr = igt_fb_map_buffer(fb->fd, fb);
+ igt_assert(ptr);
+ map = ptr;
+
+ /*
+ * Framebuffers are often uncached, which can make byte-wise accesses
+ * very slow. We copy each line of the FB into a local buffer to speed
+ * up the hashing.
+ */
+ line = malloc(stride);
+ if (!line) {
+ munmap(map, fb->size);
+ return -ENOMEM;
+ }
+
+ hash = FNV1a_OFFSET_BIAS;
+
+ for (y = 0; y < fb->height; y++, ptr += stride) {
+
+ igt_memcpy_from_wc(line, ptr, fb->width * cpp);
+
+ for (x = 0; x < fb->width * cpp; x++) {
+ hash ^= line[x];
+ hash *= FNV1a_PRIME;
+ }
+ }
+
+ crc->n_words = 1;
+ crc->crc[0] = hash;
+
+ free(line);
+ igt_fb_unmap_buffer(fb, map);
+
+ return 0;
+}
+
/**
* igt_format_is_yuv:
* @drm_format: drm fourcc
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__ */
--
2.28.0
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