Re: [PATCH v4 i-g-t] tests/kms: increase max threshold time for edid read

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On 08/14/2017 07:40 AM, Daniel Vetter wrote:
On Thu, Aug 10, 2017 at 10:50:19AM -0700, clinton.a.taylor@xxxxxxxxx wrote:
From: Clint Taylor <clinton.a.taylor@xxxxxxxxx>

Current 50ms max threshold timing for an EDID read is very close to the
actual time for a 2 block HDMI EDID read. Adjust the timings base on
connector type as DP reads are at 1 MBit and HDMI at 100K bit. If an LSPcon
is connected to device under test the -l option should be passed to update
the threshold timing to allow the LSPcon to read the EDID at the HDMI
timing. The -l option should be used when LSPcon is on the motherboard or
if a USB_C->HDMI converter is present

V2: Adjust timings based on connector type, EDID size, and Add an option to
specify if an LSPcon is present.
V3: Add bugzilla to commit message
V4: remove edid_size check from HDMI multiplier. Fixes DVI on HDMI.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=100047

Cc: Daniel Vetter <daniel.vetter@xxxxxxxxx>
Cc: Marta Lofstedt <marta.lofstedt@xxxxxxxxx>
Signed-off-by: Clint Taylor <clinton.a.taylor@xxxxxxxxx>
---
  tests/kms_sysfs_edid_timing.c | 74 +++++++++++++++++++++++++++++++++++--------
  1 file changed, 60 insertions(+), 14 deletions(-)

diff --git a/tests/kms_sysfs_edid_timing.c b/tests/kms_sysfs_edid_timing.c
index 1201388..0382610 100644
--- a/tests/kms_sysfs_edid_timing.c
+++ b/tests/kms_sysfs_edid_timing.c
@@ -26,21 +26,46 @@
  #include <fcntl.h>
  #include <sys/stat.h>
-#define THRESHOLD_PER_CONNECTOR 10
-#define THRESHOLD_TOTAL		50
-#define CHECK_TIMES		15
+#define THRESHOLD_FOR_EMPTY_CONNECTOR	10
+#define THRESHOLD_PER_EDID_BLOCK		5
+#define HDMI_THRESHOLD_MULTIPLIER		10
+#define CHECK_TIMES				10
IGT_TEST_DESCRIPTION("This check the time we take to read the content of all "
  		     "the possible connectors. Without the edid -ENXIO patch "
  		     "(http://permalink.gmane.org/gmane.comp.video.dri.devel/62083), "
-		     "we sometimes take a *really* long time. "
-		     "So let's just check for some reasonable timing here");
+		     "we sometimes take a *really* long time. So let's check "
+		     "an approximate time per edid block based on connector "
+		     "type. The -l option adjusts DP timing to reflect HDMI read "
+		     "timings from LSPcon.");
+
+/* The -l option has been added to correctly handle timings when an LSPcon is
+ * present. This could be on the platform itself or in a USB_C->HDMI converter.
+ * With LSPCon EDID read timing will need to change from the 1 Mbit AUX
+ * bus speed to the 100 Kbit HDMI DDC bus speed
This is blantantly wrong. EDID reads are done at 100kbit, even over dp
aux. There's some panels which have forgoe the i2c bus that
i2c-over-dp-aux drivers and givey ou the EDID a bit faster, but edids read
at 100kbit.

Actually most modern devices deliver DP EDID much faster than 100kbit. I have several 4K DP monitors that deliver 256 bytes EDID in < 8ms. eDP panels deliver 128 bytes in <4 ms. I also have seen devices that takes almost 50ms to deliver a 128 byte EDID block.

From kms_sysfs_edid_timing to a Asus MG24UQ monitor:
card0-DP-3: mean.max 7758610.00ns, 7758.61us, 7.76ms, mean.avg 7758610.00ns, 7758.61us, 7.76ms, edid_size 256, threshold 10

showing < 8ms to read 2 blocks of EDID.

From kms_sysfs_edid_timing connected to a QD980B DP analyzer:
card0-DP-3: mean.max 74251273.00ns, 74251.27us, 74.25ms, mean.avg 74251273.00ns, 74251.27us, 74.25ms, edid_size 256, threshold 10

showing > 74ms to read 2 blocks of EDID.

These times were confirmed with a Unigraf DPA400 to confirm both timing and that 256 bytes of data were transferred.


That means 25ms per edid block and no special cases anywhere. I think you
can still keep the 10ms for basic probe (but really shouldn't be needed).

Note your limits are off by 2x, since you use 50ms per 128b edid block. We
can totally read a CEA edid with 2 blocks in 50ms.
A single value like 25ms has been proven not to be enough time depending on the downstream device and connector type.
-Daniel

+ */
+bool lspcon_present;
+static int opt_handler(int opt, int opt_index, void *data)
+{
+	if (opt == 'l') {
+		lspcon_present = true;
+		igt_info("set LSPcon present on DP ports\n");
+	}
-igt_simple_main
+	return 0;
+}
+
+int main(int argc, char **argv)
  {
  	DIR *dirp;
  	struct dirent *de;
+	lspcon_present = false;
+
+	igt_simple_init_parse_opts(&argc, argv, "l", NULL, NULL,
+				      opt_handler, NULL);
+
+	igt_skip_on_simulation();
dirp = opendir("/sys/class/drm");
  	igt_assert(dirp != NULL);
@@ -49,17 +74,34 @@ igt_simple_main
  		struct igt_mean mean = {};
  		struct stat st;
  		char path[PATH_MAX];
-		int i;
+		char edid_path[PATH_MAX];
+		char edid[512]; /* enough for 4 block edid */
+		unsigned long edid_size = 0;
+		int i, fd_edid;
+		unsigned int threshold = 0;
if (*de->d_name == '.')
  			continue;;
snprintf(path, sizeof(path), "/sys/class/drm/%s/status",
  				de->d_name);
+		snprintf(edid_path, sizeof(edid_path), "/sys/class/drm/%s/edid",
+				de->d_name);
if (stat(path, &st))
  			continue;
+ fd_edid = open(edid_path, O_RDONLY);
+		if (fd_edid == -1) {
+			igt_warn("Read Error EDID\n");
+			continue;
+		}
+
+		edid_size = read(fd_edid, edid, 512);
+		threshold = THRESHOLD_PER_EDID_BLOCK * (edid_size / 128);
+		if (lspcon_present || !strncmp(de->d_name, "card0-HDMI", 10))
+			threshold *= HDMI_THRESHOLD_MULTIPLIER;
+
  		igt_mean_init(&mean);
  		for (i = 0; i < CHECK_TIMES; i++) {
  			struct timespec ts = {};
@@ -76,22 +118,26 @@ igt_simple_main
  		}
igt_debug("%s: mean.max %.2fns, %.2fus, %.2fms, "
-			  "mean.avg %.2fns, %.2fus, %.2fms\n",
+			  "mean.avg %.2fns, %.2fus, %.2fms, "
+			  "edid_size %lu, threshold %d\n",
  			  de->d_name,
  			  mean.max, mean.max / 1e3, mean.max / 1e6,
-			  mean.mean, mean.mean / 1e3, mean.mean / 1e6);
+			  mean.mean, mean.mean / 1e3, mean.mean / 1e6,
+			  edid_size, threshold);
- if (mean.max > (THRESHOLD_PER_CONNECTOR * 1e6)) {
+		if (edid_size == 0 &&
+		   (mean.max > (THRESHOLD_FOR_EMPTY_CONNECTOR * 1e6))) {
  			igt_warn("%s: probe time exceed 10ms, "
  				 "max=%.2fms, avg=%.2fms\n", de->d_name,
  				 mean.max / 1e6, mean.mean / 1e6);
  		}
-		igt_assert_f(mean.mean < (THRESHOLD_TOTAL * 1e6),
-			     "%s: average probe time exceeded 50ms, "
-			     "max=%.2fms, avg=%.2fms\n", de->d_name,
+		if (edid_size > 0)
+			igt_assert_f(mean.mean < (threshold * 1e6),
+			     "%s: average probe time exceeded %dms, "
+			     "max=%.2fms, avg=%.2fms\n", de->d_name, threshold,
  			     mean.max / 1e6, mean.mean / 1e6);
}
  	closedir(dirp);
-
+	igt_exit();
  }
--
1.9.1

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