[v2] tests/kms_vrr: add support for full range refresh rate testing

[Lee Shawn C <shawn.c.lee@intel.com>]

Currently, kms_vrr tests fixed step increments within the VRR range.
To better validate hardware stability and potential issues across the
entire spectrum, this patch adds a 'full-range' testing mode.

When the full-range flag is enabled, the test will:
1. Iterate from the maximum to the minimum refresh rate (stepping by 1).
2. For standard testing, maintain the existing behavior of incrementing
   from minimum to maximum using the defined step size.

v2: Fix build failure by adding documentation for the new subtest.

Signed-off-by: Lee Shawn C <shawn.c.lee@intel.com>
---
 tests/kms_vrr.c | 32 ++++++++++++++++++++++++++------
 1 file changed, 26 insertions(+), 6 deletions(-)

diff --git a/tests/kms_vrr.c b/tests/kms_vrr.c
index 6043d40f1d74..b8a8c6aa79ed 100644
--- a/tests/kms_vrr.c
+++ b/tests/kms_vrr.c
@@ -66,6 +66,9 @@
  * Description: Test to create a Virtual Mode in VRR range and switch to it
  * 		without a full modeset.
  *
+ * SUBTEST: seamless-rr-switch-virtual-full
+ * Description: Vrr seamless refresh rate switch for virtual modes using full range
+ *
  * SUBTEST: lobf
  * Description: Test to validate link-off between active frames in non-psr
  *              operation
@@ -93,9 +96,10 @@ enum {
 	TEST_FLIPLINE = 1 << 3,
 	TEST_SEAMLESS_VRR = 1 << 4,
 	TEST_SEAMLESS_DRRS = 1 << 5,
-	TEST_SEAMLESS_VIRTUAL_RR = 1 << 6,
-	TEST_FASTSET = 1 << 7,
-	TEST_MAXMIN = 1 << 8,
+	TEST_SEAMLESS_VIRTUAL_RR_FAST = 1 << 6,
+	TEST_SEAMLESS_VIRTUAL_RR_FULL = 1 << 7,
+	TEST_FASTSET = 1 << 8,
+	TEST_MAXMIN = 1 << 9,
 	TEST_LINK_OFF = 1 << 10,
 	TEST_NEGATIVE = 1 << 11,
 	TEST_FORCE_RR = 1 << 12,
@@ -754,10 +758,12 @@ test_seamless_virtual_rr_basic(data_t *data, igt_crtc_t *crtc,
 			       igt_output_t *output, uint32_t flags)
 {
 	uint32_t result;
-	unsigned int vrefresh;
+	int vrefresh;
 	uint64_t rate[] = {0};
 	uint32_t step_size;
+	int start, end, step;
 	drmModeModeInfo virtual_mode;
+	bool full_vrr_range = !!(flags & TEST_SEAMLESS_VIRTUAL_RR_FULL);
 
 	igt_info("Use HIGH_RR Mode as default\n");
 	kmstest_dump_mode(&data->switch_modes[HIGH_RR_MODE]);
@@ -795,7 +801,17 @@ test_seamless_virtual_rr_basic(data_t *data, igt_crtc_t *crtc,
 		   (((data->range.max + data->range.min) / 2) + step_size) :
 		   data->range.min + step_size;
 
-	for ( ; vrefresh < data->range.max; vrefresh += step_size) {
+	if (full_vrr_range) {
+		start = data->range.max;
+		end = data->range.min;
+		step = -1;
+	} else {
+		start = data->range.min;
+		end = data->range.max;
+		step = step_size;
+	}
+
+	for (vrefresh = start; (step > 0) ? (vrefresh <= end) : (vrefresh >= end); vrefresh += step) {
 		virtual_rr_vrr_range_mode(&virtual_mode, vrefresh);
 
 		igt_info("Requesting Virtual Mode with Refresh Rate (%u Hz): \n", vrefresh);
@@ -1103,7 +1119,11 @@ int igt_main_args("drs:", long_opts, help_str, opt_handler, &data)
 
 		igt_describe("Test to switch to any custom virtual mode in VRR range without modeset.");
 		igt_subtest_with_dynamic("seamless-rr-switch-virtual")
-			run_vrr_test(&data, test_seamless_virtual_rr_basic, TEST_SEAMLESS_VIRTUAL_RR);
+			run_vrr_test(&data, test_seamless_virtual_rr_basic, TEST_SEAMLESS_VIRTUAL_RR_FAST);
+
+		igt_describe("Test to switch to all virtual modes in VRR range without modeset.");
+		igt_subtest_with_dynamic("seamless-rr-switch-virtual-full")
+			run_vrr_test(&data, test_seamless_virtual_rr_basic, TEST_SEAMLESS_VIRTUAL_RR_FULL);
 
 		igt_describe("Test to validate the link-off between active frames in "
 			     "non-PSR operation.");
-- 
2.34.1