[PATCH i-g-t 1/2] tests/chamelium: Skip suspend/resume test with unreliable hotplug event

[Paul Kocialkowski]

It may occur that a hotplug uevent is detected at resume, even though it
does not indicate that an actual hotplug happened. This is the case when
link training fails on any other connector.

There is currently no way to distinguish what connector caused a hotplug
uevent, nor what the reason for that uevent really is. This makes it
impossible to find out whether the test actually passed or not.

To circumvent this problem, the link status of each connector is
collected before and after suspend and compared to skip the test if
the state was good before and turned to bad after resume.

This only concerns the EDID change test, where we cannot check the
connector state (that is not supposed to have changed). For actual
hotplug tests, the tests should be safe since they check each
connector's state after receiving the uevent.

The situation described here happens with DP-VGA bridges that fail link
training after resume, as they need some more time to response on their
AUX channel.

Signed-off-by: Paul Kocialkowski <paul.kocialkowski at linux.intel.com>
---
 tests/chamelium.c | 35 +++++++++++++++++++++++++++++++++++
 1 file changed, 35 insertions(+)

diff --git a/tests/chamelium.c b/tests/chamelium.c
index e26f0557..8af33aaa 100644
--- a/tests/chamelium.c
+++ b/tests/chamelium.c
@@ -87,6 +87,31 @@ get_precalculated_crc(struct chamelium_port *port, int w, int h)
 }
 
 static void
+get_connectors_link_status_failed(data_t *data, bool *link_status_failed)
+{
+	drmModeConnector *connector;
+	uint64_t link_status;
+	drmModePropertyPtr prop;
+	int p;
+
+	for (p = 0; p < data->port_count; p++) {
+		connector = chamelium_port_get_connector(data->chamelium,
+							 data->ports[p], false);
+
+		igt_assert(kmstest_get_property(data->drm_fd,
+						connector->connector_id,
+						DRM_MODE_OBJECT_CONNECTOR,
+						"link-status", NULL,
+						&link_status, &prop));
+
+		link_status_failed[p] = link_status == DRM_MODE_LINK_STATUS_BAD;
+
+		drmModeFreeProperty(prop);
+		drmModeFreeConnector(connector);
+	}
+}
+
+static void
 require_connector_present(data_t *data, unsigned int type)
 {
 	int i;
@@ -310,6 +335,8 @@ test_suspend_resume_edid_change(data_t *data, struct chamelium_port *port,
 				int alt_edid_id)
 {
 	struct udev_monitor *mon = igt_watch_hotplug();
+	bool link_status_failed[2][data->port_count];
+	int p;
 
 	reset_state(data, port);
 
@@ -326,8 +353,16 @@ test_suspend_resume_edid_change(data_t *data, struct chamelium_port *port,
 	 */
 	chamelium_port_set_edid(data->chamelium, port, alt_edid_id);
 
+	get_connectors_link_status_failed(data, link_status_failed[0]);
+
 	igt_system_suspend_autoresume(state, test);
+
 	igt_assert(igt_hotplug_detected(mon, HOTPLUG_TIMEOUT));
+
+	get_connectors_link_status_failed(data, link_status_failed[1]);
+
+	for (p = 0; p < data->port_count; p++)
+		igt_skip_on(!link_status_failed[0][p] && link_status_failed[1][p]);
 }
 
 static igt_output_t *
-- 
2.13.2