[igt-dev] [PATCH i-g-t 1/2] lib/igt_debugfs: Add igt_crc_get_previous()

[Ville Syrjala <ville.syrjala@linux.intel.com>]

From: Ville Syrjälä <ville.syrjala@linux.intel.com>

Add a new helper to return the most recently captured crc
without waiting for the current frame's crc to be captured.
Useful when we pipeline flips and crc captures more deeply
to eliminate dead time between the flips.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
---
 lib/igt_debugfs.c | 29 +++++++++++++++++++++++++++++
 lib/igt_debugfs.h |  1 +
 2 files changed, 30 insertions(+)

diff --git a/lib/igt_debugfs.c b/lib/igt_debugfs.c
index 8cac9d1e148e..844763d51c3e 100644
--- a/lib/igt_debugfs.c
+++ b/lib/igt_debugfs.c
@@ -970,6 +970,35 @@ igt_pipe_crc_get_current(int drm_fd, igt_pipe_crc_t *pipe_crc, igt_crc_t *crc)
 	crc_sanity_checks(pipe_crc, crc);
 }
 
+/**
+ * igt_pipe_crc_get_previous:
+ * @drm_fd: Pointer to drm fd for vblank counter
+ * @pipe_crc: pipe CRC object
+ * @crc: buffer pointer for the captured CRC value
+ *
+ * Same as igt_pipe_crc_get_current(), but will return the crc
+ * most recently captured (ie. does not wait an extra frame for
+ * the crc computation for the current frame to finish).
+ */
+void
+igt_pipe_crc_get_previous(int drm_fd, igt_pipe_crc_t *pipe_crc, igt_crc_t *crc)
+{
+	unsigned vblank = kmstest_get_vblank(drm_fd, pipe_crc->pipe, 0);
+
+	do {
+		read_one_crc(pipe_crc, crc);
+
+		/* Only works with valid frame counter */
+		if (!crc->has_valid_frame) {
+			igt_pipe_crc_drain(pipe_crc);
+			igt_pipe_crc_get_single(pipe_crc, crc);
+			return;
+		}
+	} while (igt_vblank_before(crc->frame, vblank));
+
+	crc_sanity_checks(pipe_crc, crc);
+}
+
 /**
  * igt_pipe_crc_collect_crc:
  * @pipe_crc: pipe CRC object
diff --git a/lib/igt_debugfs.h b/lib/igt_debugfs.h
index 1e0cc108d6fb..69f65f789bd3 100644
--- a/lib/igt_debugfs.h
+++ b/lib/igt_debugfs.h
@@ -104,6 +104,7 @@ int igt_pipe_crc_get_crcs(igt_pipe_crc_t *pipe_crc, int n_crcs,
 void igt_pipe_crc_drain(igt_pipe_crc_t *pipe_crc);
 void igt_pipe_crc_get_single(igt_pipe_crc_t *pipe_crc, igt_crc_t *out_crc);
 void igt_pipe_crc_get_current(int drm_fd, igt_pipe_crc_t *pipe_crc, igt_crc_t *crc);
+void igt_pipe_crc_get_previous(int drm_fd, igt_pipe_crc_t *pipe_crc, igt_crc_t *crc);
 
 void igt_pipe_crc_collect_crc(igt_pipe_crc_t *pipe_crc, igt_crc_t *out_crc);
 
-- 
2.24.1

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