[PATCH i-g-t v3 2/2] tests/kms_setmode: Add basic-no-cpu-idle subtest

[Jason-JH Lin <jason-jh.lin@mediatek.com>]

Add a new subtest that disables CPU deep sleep to eliminate wakeup
latency interference during vblank timestamp verification.

This allows platforms without get_scanout_position() to verify their
timestamp accuracy is correct, separate from CPU idle interference.

The original "basic" test remains unchanged to detect any timestamp
issues including CPU idle interference, while "basic-no-cpu-idle"
specifically tests timestamp accuracy without external interference.

Once get_scanout_position() is implemented, the vblank timestamp
will be accurately compensated regardless of CPU idle states.

Signed-off-by: Jason-JH Lin <jason-jh.lin@mediatek.com>
---
 tests/kms_setmode.c | 37 +++++++++++++++++++++++++++++++++++++
 1 file changed, 37 insertions(+)

diff --git a/tests/kms_setmode.c b/tests/kms_setmode.c
index ef0082dbf70b..a65ea8b232fc 100644
--- a/tests/kms_setmode.c
+++ b/tests/kms_setmode.c
@@ -42,6 +42,7 @@
 #include <math.h>
 
 #include "i915/intel_drrs.h"
+#include "igt_pm.h"
 #include "xe/xe_query.h"
 
 /**
@@ -49,6 +50,13 @@
  * Description: Tests the vblank timing by iterating through all valid crtc/connector
  *              combinations
  *
+ * SUBTEST: basic-no-cpu-idle
+ * Description: Tests vblank timing with CPU deep sleep disabled to verify
+ *              timestamp accuracy without CPU idle interference. This test
+ *              is for platforms lacking HW/SW get_scanout_position() support,
+ *              allowing them to verify vblank timestamp correctness without
+ *              external CPU wakeup latency interference.
+ *
  * SUBTEST: basic-clone-single-crtc
  * Description: Test allows the use of a single CRTC for two connectors, such as VGA/HDMI,
  *		VGA/DP, and HDMI/HDMI
@@ -1034,6 +1042,11 @@ static void run_test(const struct test_config *tconf)
 		test_combinations(tconf, connector_num);
 }
 
+static void restore_cpu_deep_sleep_at_exit(int sig)
+{
+	igt_pm_enable_cpu_deep_sleep();
+}
+
 static int opt_handler(int opt, int opt_index, void *data)
 {
 	switch (opt) {
@@ -1105,6 +1118,30 @@ int igt_main_args("det:", NULL, help_str, opt_handler, NULL)
 		}
 	}
 
+	/*
+	 * This subtest disables CPU deep sleep to eliminate wakeup latency
+	 * interference during vblank timestamp verification.
+	 *
+	 * NOTE: This is for platforms that have not yet implemented
+	 * get_scanout_position(). Once get_scanout_position() is properly
+	 * implemented, the vblank timestamp will be accurately compensated
+	 * regardless of CPU idle states, and this test becomes redundant
+	 * with the standard "basic" test.
+	 */
+	igt_describe("Tests vblank timing with CPU deep sleep disabled");
+	igt_subtest_with_dynamic("basic-no-cpu-idle") {
+		struct test_config tconf = {
+			.flags		= TEST_TIMINGS,
+			.name		= "basic-no-cpu-idle",
+			.resources	= drm_resources,
+		};
+
+		igt_require_f(igt_pm_disable_cpu_deep_sleep(),
+			      "Platform does not support CPU idle control\n");
+		igt_install_exit_handler(restore_cpu_deep_sleep_at_exit);
+		run_test(&tconf);
+	}
+
 	igt_fixture() {
 		drmModeFreeResources(drm_resources);
 		drm_close_driver(drm_fd);
-- 
2.43.0