lib/igt_debugfs: Add igt_pipe_crc_get_single and igt_pipe_crc_drain, v4.

Collecting CRC may result in a modeset and extra vblank waits. On some
tests this will increase the runtime a lot, so it makes sense to
keep it enabled, and only collect the most recent CRC when needed.

Changes since v1:
- Fix read_crc semantics. (Ville)
Changes since v2:
- Remove EAGAIN assert, can be reached from drain_crc.
Changes since v3:
- Do not infinitely loop in igt_pipe_crc_drain().

Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Reviewed-by: Mika Kahola <mika.kahola@intel.com> #v2
Tested-by: Vidya Srinivas <vidya.srinivas@intel.com>

3 files changed, 76 insertions, 24 deletions

diff --git a/lib/igt_debugfs.c b/lib/igt_debugfs.c
index 1aec079c..e2b15f9b 100644
--- a/lib/igt_debugfs.c
+++ b/lib/igt_debugfs.c
@@ -706,15 +706,12 @@ static int read_crc(igt_pipe_crc_t *pipe_crc, igt_crc_t *out)
 	bytes_read = read(pipe_crc->crc_fd, &buf, MAX_LINE_LEN);
 	igt_reset_timeout();
 
-	if (bytes_read < 0 && errno == EAGAIN)
-		igt_assert(pipe_crc->flags & O_NONBLOCK);
-
 	if (bytes_read < 0)
-		bytes_read = 0;
-
-	buf[bytes_read] = '\0';
+		bytes_read = -errno;
+	else
+		buf[bytes_read] = '\0';
 
-	if (bytes_read && !pipe_crc_init_from_string(pipe_crc, out, buf))
+	if (bytes_read > 0 && !pipe_crc_init_from_string(pipe_crc, out, buf))
 		return -EINVAL;
 
 	return bytes_read;
@@ -722,7 +719,9 @@ static int read_crc(igt_pipe_crc_t *pipe_crc, igt_crc_t *out)
 
 static void read_one_crc(igt_pipe_crc_t *pipe_crc, igt_crc_t *out)
 {
-	while (read_crc(pipe_crc, out) == 0)
+	int ret;
+
+	while ((ret = read_crc(pipe_crc, out)) <= 0 && ret != -EINVAL)
 		usleep(1000);
 }
 
@@ -854,6 +853,68 @@ void igt_pipe_crc_collect_crc(igt_pipe_crc_t *pipe_crc, igt_crc_t *out_crc)
 	crc_sanity_checks(out_crc);
 }
 
+/**
+ * igt_pipe_crc_drain:
+ * @pipe_crc: pipe CRC object
+ *
+ * Discards all currently queued CRC values from @pipe_crc. This function does
+ * not block, and is useful to flush @pipe_crc. Afterwards you can get a fresh
+ * CRC with igt_pipe_crc_get_single().
+ */
+void igt_pipe_crc_drain(igt_pipe_crc_t *pipe_crc)
+{
+	int ret;
+	igt_crc_t crc;
+
+	fcntl(pipe_crc->crc_fd, F_SETFL, pipe_crc->flags | O_NONBLOCK);
+
+	do {
+		ret = read_crc(pipe_crc, &crc);
+	} while (ret > 0 || ret == -EINVAL);
+
+	fcntl(pipe_crc->crc_fd, F_SETFL, pipe_crc->flags);
+}
+
+/**
+ * igt_pipe_crc_get_single:
+ * @pipe_crc: pipe CRC object
+ * @crc: buffer pointer for the captured CRC value
+ *
+ * Read a single @crc from @pipe_crc. This function does not block
+ * when nonblocking CRC is requested, and will return false if no CRC
+ * can be captured.
+ *
+ * If opened in blocking mode it will always block until a new CRC is read, like
+ * igt_pipe_crc_collect_crc().
+ *
+ * Callers must start and stop the capturing themselves by calling
+ * igt_pipe_crc_start() and igt_pipe_crc_stop(). For one-shot CRC collecting
+ * look at igt_pipe_crc_collect_crc().
+ *
+ * If capturing has been going on for a while and a fresh crc is required,
+ * you will need to call igt_pipe_crc_drain() first to remove stale entries.
+ *
+ * Returns:
+ * Whether a crc is captured, only false in non-blocking mode.
+ */
+bool
+igt_pipe_crc_get_single(igt_pipe_crc_t *pipe_crc, igt_crc_t *crc)
+{
+	bool found = true;
+
+	if (pipe_crc->flags & O_NONBLOCK) {
+		int ret = read_crc(pipe_crc, crc);
+
+		found = ret > 0;
+	} else
+		read_one_crc(pipe_crc, crc);
+
+	if (found)
+		crc_sanity_checks(crc);
+
+	return found;
+}
+
 /*
  * Drop caches
  */
diff --git a/lib/igt_debugfs.h b/lib/igt_debugfs.h
index d90dd7a6..8d25abfe 100644
--- a/lib/igt_debugfs.h
+++ b/lib/igt_debugfs.h
@@ -130,6 +130,8 @@ void igt_pipe_crc_stop(igt_pipe_crc_t *pipe_crc);
 __attribute__((warn_unused_result))
 int igt_pipe_crc_get_crcs(igt_pipe_crc_t *pipe_crc, int n_crcs,
 			  igt_crc_t **out_crcs);
+void igt_pipe_crc_drain(igt_pipe_crc_t *pipe_crc);
+bool igt_pipe_crc_get_single(igt_pipe_crc_t *pipe_crc, igt_crc_t *out_crc);
 void igt_pipe_crc_collect_crc(igt_pipe_crc_t *pipe_crc, igt_crc_t *out_crc);
 
 void igt_hpd_storm_set_threshold(int fd, unsigned int threshold);
diff --git a/tests/kms_cursor_legacy.c b/tests/kms_cursor_legacy.c
index 5011e78e..d0a28b3c 100644
--- a/tests/kms_cursor_legacy.c
+++ b/tests/kms_cursor_legacy.c
@@ -1276,7 +1276,7 @@ static void flip_vs_cursor_busy_crc(igt_display_t *display, bool atomic)
 	enum pipe pipe = find_connected_pipe(display, false);
 	igt_pipe_t *pipe_connected = &display->pipes[pipe];
 	igt_plane_t *plane_primary = igt_pipe_get_plane_type(pipe_connected, DRM_PLANE_TYPE_PRIMARY);
-	igt_crc_t crcs[2];
+	igt_crc_t crcs[2], test_crc;
 
 	if (atomic)
 		igt_require(display->is_atomic);
@@ -1290,7 +1290,7 @@ static void flip_vs_cursor_busy_crc(igt_display_t *display, bool atomic)
 
 	igt_display_commit2(display, display->is_atomic ? COMMIT_ATOMIC : COMMIT_LEGACY);
 
-	pipe_crc = igt_pipe_crc_new_nonblock(display->drm_fd, pipe, INTEL_PIPE_CRC_SOURCE_AUTO);
+	pipe_crc = igt_pipe_crc_new(display->drm_fd, pipe, INTEL_PIPE_CRC_SOURCE_AUTO);
 
 	set_cursor_on_pipe(display, pipe, &cursor_fb);
 	igt_display_commit2(display, COMMIT_UNIVERSAL);
@@ -1322,9 +1322,6 @@ static void flip_vs_cursor_busy_crc(igt_display_t *display, bool atomic)
 	/* Disable cursor, and immediately queue a flip. Check if resulting crc is correct. */
 	for (int i = 1; i >= 0; i--) {
 		igt_spin_t *spin;
-		igt_crc_t *received_crcs = NULL;
-		int ncrcs;
-		static const int max_crcs = 8;
 
 		spin = igt_spin_batch_new(display->drm_fd, 0, 0,
 					  fb_info[1].gem_handle);
@@ -1336,7 +1333,8 @@ static void flip_vs_cursor_busy_crc(igt_display_t *display, bool atomic)
 
 		igt_assert_eq(get_vblank(display->drm_fd, pipe, 0), vblank_start);
 
-		ncrcs = igt_pipe_crc_get_crcs(pipe_crc, max_crcs, &received_crcs);
+		igt_pipe_crc_drain(pipe_crc);
+		igt_pipe_crc_get_single(pipe_crc, &test_crc);
 
 		igt_spin_batch_free(display->drm_fd, spin);
 
@@ -1349,16 +1347,7 @@ static void flip_vs_cursor_busy_crc(igt_display_t *display, bool atomic)
 		igt_plane_set_fb(plane_primary, &fb_info[0]);
 		igt_display_commit2(display, COMMIT_UNIVERSAL);
 
-		/*
-		 * We collect the crc nonblockingly, and should have at least 1
-		 * but not so many crcs that we overflow. Last CRC is the only
-		 * one we care about here. Other CRCs may have been from before
-		 * the cursor update and can contain garbage.
-		 */
-		igt_assert(ncrcs > 0 && ncrcs < max_crcs);
-
-		igt_assert_crc_equal(&crcs[i], &received_crcs[ncrcs - 1]);
-		free(received_crcs);
+		igt_assert_crc_equal(&crcs[i], &test_crc);
 	}
 
 	igt_remove_fb(display->drm_fd, &fb_info[1]);