[PATCH i-g-t v2 1/2] tests/kms_vrr: Start virtual RR test above midpoint to avoid mode fallback

[Naladala Ramanaidu <ramanaidu.naladala@intel.com>]

Starting from low_rr + step_size could cause the driver to fall back
to a lower physical mode due to proximity to the lower bound of the
VRR range. This results in an unintended clock change, which violates
the expectation of seamless VRR behavior.

To address this, the test now starts from above the midpoint of the
VRR range when multiple modes are available. This ensures the virtual
refresh rate remains safely within the active mode's VRR range and
avoids triggering a mode switch.

v2: Change logic to ternary operation. (Santhosh)

Signed-off-by: Naladala Ramanaidu <ramanaidu.naladala@intel.com>
---
 tests/kms_vrr.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/tests/kms_vrr.c b/tests/kms_vrr.c
index bcb756202..57691ccd5 100644
--- a/tests/kms_vrr.c
+++ b/tests/kms_vrr.c
@@ -851,7 +851,16 @@ test_seamless_virtual_rr_basic(data_t *data, enum pipe pipe, igt_output_t *outpu
 	/* Switch to Virtual RR */
 	virtual_mode = *igt_output_get_mode(output);
 
-	for (vrefresh = data->range.min + step_size; vrefresh < data->range.max; vrefresh += step_size) {
+	/*
+	 * Start virtual RR testing from above the midpoint of the VRR range when multiple
+	 * modes are available. This avoids the driver mode adjustment. which can cause an
+	 * unintended clock change.
+	 */
+	vrefresh = (output->config.connector->count_modes > 1) ?
+		   (((data->range.max + data->range.min) / 2) + step_size) :
+		   data->range.min + step_size;
+
+	for ( ; vrefresh < data->range.max; vrefresh += step_size) {
 		virtual_rr_vrr_range_mode(&virtual_mode, vrefresh);
 
 		igt_info("Requesting Virtual Mode with Refresh Rate (%u Hz): \n", vrefresh);
-- 
2.43.0