[igt-dev] [PATCH v2 i-g-t] tests/chamelium: Add test for hotplug workaround

[José Roberto de Souza]

It is know that some unpowered type-c dongles can take some time to
boot and be responsible in the DDC/aux transaction lines so a
workaround was implemented in kernel(drm/i915: Enable hotplug retry)
to fix it but is possible that this could happen to other DP sinks.

So this test will try to simulate the sceneario described above, it
will disable the DDC lines and plug the connector, the hotplug should
fail and then enabling the DDC lines kernel should report the
connector as connected.

The workaround will reprobe connector after 1 second after kernel
gives up on the first try to probe the connector, so that is why a
smaller timeout to detect hotplug was needed.

v2:
- Removing igt_assert() from the igt_hotplug_detected() when checking
if device can act on hotplug fast enough
- Checking time spend between hotplug and the enabling of DDC lines
(Imre)

Cc: Imre Deak <imre.deak at intel.com>
Signed-off-by: José Roberto de Souza <jose.souza at intel.com>
---
 tests/kms_chamelium.c | 110 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 110 insertions(+)

diff --git a/tests/kms_chamelium.c b/tests/kms_chamelium.c
index c2090037..c79516ef 100644
--- a/tests/kms_chamelium.c
+++ b/tests/kms_chamelium.c
@@ -45,6 +45,8 @@ typedef struct {
 
 #define HOTPLUG_TIMEOUT 20 /* seconds */
 
+#define FAST_HOTPLUG_TIMEOUT (1) /* second */
+
 #define HPD_STORM_PULSE_INTERVAL_DP 100 /* ms */
 #define HPD_STORM_PULSE_INTERVAL_HDMI 200 /* ms */
 
@@ -107,6 +109,21 @@ reprobe_connector(data_t *data, struct chamelium_port *port)
 	return status;
 }
 
+static drmModeConnection
+connector_status_get(data_t *data, struct chamelium_port *port)
+{
+	drmModeConnector *connector;
+	drmModeConnection status;
+
+	igt_debug("Getting connector state %s...\n", chamelium_port_get_name(port));
+	connector = chamelium_port_get_connector(data->chamelium, port, false);
+	igt_assert(connector);
+	status = connector->connection;
+
+	drmModeFreeConnector(connector);
+	return status;
+}
+
 static void
 wait_for_connector(data_t *data, struct chamelium_port *port,
 		   drmModeConnection status)
@@ -253,6 +270,96 @@ test_basic_hotplug(data_t *data, struct chamelium_port *port, int toggle_count)
 	igt_hpd_storm_reset(data->drm_fd);
 }
 
+static void
+test_fast_hotplug_handling(data_t *data, struct chamelium_port *port,
+			   struct udev_monitor *mon)
+{
+	drmModeConnection status;
+
+	igt_flush_hotplugs(mon);
+	chamelium_plug(data->chamelium, port);
+	igt_hotplug_detected(mon, FAST_HOTPLUG_TIMEOUT);
+	status = connector_status_get(data, port);
+	igt_require(status == DRM_MODE_CONNECTED);
+
+	igt_flush_hotplugs(mon);
+	chamelium_unplug(data->chamelium, port);
+	igt_hotplug_detected(mon, FAST_HOTPLUG_TIMEOUT);
+	status = connector_status_get(data, port);
+	igt_require(status == DRM_MODE_DISCONNECTED);
+}
+
+/*
+ * Test kernel workaround for sinks that takes some time to have the DDC/aux
+ * channel responsive after the hotplug
+ */
+static void
+test_late_aux_wa(data_t *data, struct chamelium_port *port)
+{
+	struct udev_monitor *mon = igt_watch_hotplug();
+	drmModeConnection status;
+	struct timespec begin;
+	uint64_t delta_nsec;
+	uint8_t retries = 0;
+
+	/* Reset will unplug all connectors */
+	reset_state(data, NULL);
+
+	/* Check if it device can act on hotplugs fast enough for this test */
+	test_fast_hotplug_handling(data, port, mon);
+
+retry:
+	/* It is fast enough, lets disable the DDC lines and plug again */
+	igt_flush_hotplugs(mon);
+	chamelium_port_set_ddc_state(data->chamelium, port, false);
+	chamelium_plug(data->chamelium, port);
+	igt_gettime(&begin);
+	igt_assert(!chamelium_port_get_ddc_state(data->chamelium, port));
+
+	/*
+	 * Give some time to kernel try to process hotplug but it should fail
+	 */
+	igt_hotplug_detected(mon, FAST_HOTPLUG_TIMEOUT);
+	status = connector_status_get(data, port);
+	igt_assert(status == DRM_MODE_DISCONNECTED);
+
+	/*
+	 * Enable the DDC line and the kernel workaround should reprobe and
+	 * report as connected
+	 */
+	chamelium_port_set_ddc_state(data->chamelium, port, true);
+
+	/*
+	 * i915 uses the maximum timeout that each platform support to do aux
+	 * transactions, this timeout can vary from 1.6msec to 4msec and i915
+	 * driver tries the same aux transaction up to 5 times before return a
+	 * error and additionally drm helpers will ask driver to do the same aux
+	 * transaction up to 32 times, so it will take at least 256msec~640msec
+	 * to kernel give up on a sink detection.
+	 *
+	 * The workaround will be schedule to run 1 second after the driver
+	 * failed to probe the connector that signaled a hotplug, so if this
+	 * test is preempt it could fail because the workaround is already
+	 * running with the DDC lines still off, so lets try again until the
+	 * time requirement is meet.
+	 */
+	delta_nsec = igt_nsec_elapsed(&begin);
+	if (delta_nsec > (NSEC_PER_SEC * 1.3f)) {
+		igt_assert_f(retries != 5, "Test preempted too many times");
+		retries++;
+
+		/* Wait for 1 more sec to make sure the workaround finished */
+		chamelium_unplug(data->chamelium, port);
+		igt_hotplug_detected(mon, FAST_HOTPLUG_TIMEOUT);
+		goto retry;
+	}
+
+	igt_assert(chamelium_port_get_ddc_state(data->chamelium, port));
+	igt_assert(igt_hotplug_detected(mon, FAST_HOTPLUG_TIMEOUT));
+	status = connector_status_get(data, port);
+	igt_assert(status == DRM_MODE_CONNECTED);
+}
+
 static void
 test_edid_read(data_t *data, struct chamelium_port *port,
 	       int edid_id, const unsigned char *edid)
@@ -1308,6 +1415,9 @@ igt_main
 
 		connector_subtest("dp-frame-dump", DisplayPort)
 			test_display_frame_dump(&data, port);
+
+		connector_subtest("dp-late-aux-wa", DisplayPort)
+			test_late_aux_wa(&data, port);
 	}
 
 	igt_subtest_group {
-- 
2.21.0