From: Brian Starkey <brian.starkey@xxxxxxx> 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). Signed-off-by: Brian Starkey <brian.starkey@xxxxxxx> --- lib/igt_fb.c | 65 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ lib/igt_fb.h | 5 +++++ 2 files changed, 70 insertions(+) diff --git a/lib/igt_fb.c b/lib/igt_fb.c index 7404ba7c..1501006e 100644 --- a/lib/igt_fb.c +++ b/lib/igt_fb.c @@ -1705,3 +1705,68 @@ bool igt_fb_supported_format(uint32_t drm_format) return false; } + +/* + * 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_crc(struct igt_fb *fb, igt_crc_t *crc) +{ +#define FNV1a_OFFSET_BIAS 2166136261 +#define 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; + + if (fb->is_dumb) + map = kmstest_dumb_map_buffer(fb->fd, fb->gem_handle, fb->size, + PROT_READ); + else + map = gem_mmap__gtt(fb->fd, fb->gem_handle, fb->size, + PROT_READ); + ptr = map; + + /* + * 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(fb->stride); + if (!line) { + munmap(map, fb->size); + return -ENOMEM; + } + + hash = FNV1a_OFFSET_BIAS; + + for (y = 0; y < fb->height; y++, ptr += fb->stride) { + + memcpy(line, ptr, fb->stride); + + for (x = 0; x < fb->width * cpp; x++) { + hash ^= line[x]; + hash *= FNV1a_PRIME; + } + } + + crc->n_words = 1; + crc->crc[0] = hash; + + free(line); + munmap(map, fb->size); + + return 0; +#undef FNV1a_OFFSET_BIAS +#undef FNV1a_PRIME +} diff --git a/lib/igt_fb.h b/lib/igt_fb.h index 023b069d..bc615516 100644 --- a/lib/igt_fb.h +++ b/lib/igt_fb.h @@ -36,6 +36,8 @@ #include <i915_drm.h> +#include "igt_debugfs.h" + /** * igt_fb_t: * @fb_id: KMS ID of the framebuffer @@ -164,5 +166,8 @@ uint32_t igt_drm_format_to_bpp(uint32_t drm_format); const char *igt_format_str(uint32_t drm_format); bool igt_fb_supported_format(uint32_t drm_format); +/* Get a hash for a framebuffer */ +int igt_fb_get_crc(struct igt_fb *fb, igt_crc_t *crc); + #endif /* __IGT_FB_H__ */ -- 2.16.1 _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
