[PATCH i-g-t v2] tests/intel/kms_pm_backlight: Setup output before reading writing backlight

[Suraj Kandpal <suraj.kandpal@intel.com>]

Currently many pm backlight tests assume that panel will stay up until
unless we tell it to go down or AUX transactions are happening.
That is not the case, some panels when they detect that there are no
changes or commits going in, it will go to a lower power state. This
causes issue in this test like AUX suddenly timing out (mostly in
fade tests where each backlight change has a 10ms sleep and many
steps giving panel to internally go in low power state). Also since
changing backlight has its own interface it does not count as a commit
hence does not contribute to the panel staying on.
Also trying to change a backlight when panel is not up does not make sense.
To solve this setup the output and do a flip to make sure panel is not
down to simulate a real life use case on when backlight is changed.

Signed-off-by: Suraj Kandpal <suraj.kandpal@intel.com>
Reviewed-by: Karthik B S <karthik.b.s@intel.com>
---
v1 -> v2:
- Remove setup and commit function from check dpms as it is not
needed there (Karthik)

 tests/intel/kms_pm_backlight.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/tests/intel/kms_pm_backlight.c b/tests/intel/kms_pm_backlight.c
index daa70c716..f108e8387 100644
--- a/tests/intel/kms_pm_backlight.c
+++ b/tests/intel/kms_pm_backlight.c
@@ -84,6 +84,24 @@ enum {
 
 IGT_TEST_DESCRIPTION("Basic backlight sysfs test");
 
+static void setup_output_and_commit(igt_backlight_context_t *context)
+{
+	igt_output_t *output = context->output;
+	igt_display_t *display = output->display;
+	drmModeModeInfo *mode;
+	igt_plane_t *primary;
+	struct igt_fb fb;
+
+	mode = igt_output_get_mode(output);
+	igt_create_pattern_fb(display->drm_fd,
+			      mode->hdisplay, mode->vdisplay,
+			      DRM_FORMAT_XRGB8888,
+			      DRM_FORMAT_MOD_LINEAR, &fb);
+	primary = igt_output_get_plane_type(output, DRM_PLANE_TYPE_PRIMARY);
+	igt_plane_set_fb(primary, &fb);
+	igt_display_commit2(display, display->is_atomic ? COMMIT_ATOMIC : COMMIT_LEGACY);
+}
+
 static void test_and_verify(igt_backlight_context_t *context, int val)
 {
 	const int tolerance = val * TOLERANCE / 100;
@@ -133,10 +151,12 @@ static void test_fade(igt_backlight_context_t *context)
 
 	/* Fade out, then in */
 	for (i = context->max; i > 0; i -= context->max / FADESTEPS) {
+		setup_output_and_commit(context);
 		test_and_verify(context, i);
 		nanosleep(&ts, NULL);
 	}
 	for (i = 0; i <= context->max; i += context->max / FADESTEPS) {
+		setup_output_and_commit(context);
 		test_and_verify(context, i);
 		nanosleep(&ts, NULL);
 	}
-- 
2.34.1