[PATCH i-g-t v1 1/2] lib/igt_kms: Add MST bandwidth-fitting support and helpers

[Sowmiya S <sowmiya.s@intel.com>]

Add helpers to handle shared-link DP bandwidth fitting for
MST/daisy-chain configurations.

On MST hubs/daisy-chains multiple streams share one DP link
and a joint atomic commit can be rejected unless modes are
chosen to fit the link BW. This will centralizes MST detection
and fitting so tests can request fitting only when required.

Signed-off-by: Sowmiya S <sowmiya.s@intel.com>
---
 lib/igt_kms.c | 33 +++++++++++++++++++++++++++++++++
 lib/igt_kms.h |  3 +++
 2 files changed, 36 insertions(+)

diff --git a/lib/igt_kms.c b/lib/igt_kms.c
index 2d758b63c..0c7965954 100644
--- a/lib/igt_kms.c
+++ b/lib/igt_kms.c
@@ -2744,6 +2744,7 @@ static void igt_output_reset(igt_output_t *output)
 {
 	output->pending_crtc = NULL;
 	output->use_override_mode = false;
+	output->bw_fit_applied = false;
 	memset(&output->override_mode, 0, sizeof(output->override_mode));
 
 	igt_output_set_prop_value(output, IGT_CONNECTOR_CRTC_ID, 0);
@@ -3227,6 +3228,15 @@ void igt_display_require(igt_display_t *display, int drm_fd)
 
 	igt_display_reset_outputs(display);
 
+	/* Detect MST outputs after they are fully initialized */
+	for (i = 0; i < display->n_outputs; i++) {
+		if (display->outputs[i].config.connector &&
+		    igt_check_output_is_dp_mst(&display->outputs[i])) {
+			display->needs_bw_fit = true;
+			break;
+		}
+	}
+
 out:
 	LOG_UNINDENT(display);
 
@@ -5372,6 +5382,7 @@ bool __override_all_active_output_modes_to_fit_bw(igt_display_t *display,
 		int ret;
 
 		igt_output_override_mode(output, mode);
+		output->bw_fit_applied = true;
 
 		if (__override_all_active_output_modes_to_fit_bw(display, outputs, n_outputs, base + 1))
 			return true;
@@ -5441,6 +5452,9 @@ bool igt_fit_modes_in_bw(igt_display_t *display)
 {
 	int ret;
 
+	for (int i = 0; i < display->n_outputs; i++)
+		display->outputs[i].bw_fit_applied = false;
+
 	if (display->is_atomic)
 		ret = igt_display_try_commit_atomic(display,
 						    DRM_MODE_ATOMIC_TEST_ONLY |
@@ -5461,6 +5475,25 @@ bool igt_fit_modes_in_bw(igt_display_t *display)
 	return true;
 }
 
+void igt_display_fit_bw(igt_display_t *display)
+{
+	int active_mst = 0;
+
+	if (!display->needs_bw_fit)
+		return;
+	for (int i = 0; i < display->n_outputs; i++) {
+		igt_output_t *output = &display->outputs[i];
+
+		if (output->pending_crtc &&
+		    igt_check_output_is_dp_mst(output))
+			active_mst++;
+	}
+	if (active_mst < 2)
+		return;
+	igt_require_f(igt_fit_modes_in_bw(display),
+		      "No valid mode combination fits available MST link BW\n");
+}
+
 /**
  * igt_crtc_refresh:
  * @crtc: CRTC to refresh
diff --git a/lib/igt_kms.h b/lib/igt_kms.h
index fcbb6a5ad..5c60e7bb4 100644
--- a/lib/igt_kms.h
+++ b/lib/igt_kms.h
@@ -506,6 +506,7 @@ typedef struct {
 
 	/* bitmask of changed properties */
 	uint64_t changed;
+	bool bw_fit_applied;
 
 	uint32_t props[IGT_NUM_CONNECTOR_PROPS];
 	uint64_t values[IGT_NUM_CONNECTOR_PROPS];
@@ -536,6 +537,7 @@ struct _igt_display {
 	uint64_t *modifiers;
 	uint32_t *formats;
 	int format_mod_count;
+	bool needs_bw_fit;
 };
 
 typedef struct {
@@ -1286,6 +1288,7 @@ drmModePropertyBlobRes *igt_get_writeback_formats_blob(igt_output_t *output);
 uint64_t igt_get_writeback_fb_id(igt_output_t *output);
 void igt_detach_crtc(igt_display_t *display, igt_output_t *output);
 void igt_get_and_wait_out_fence(igt_output_t *output);
+void igt_display_fit_bw(igt_display_t *display);
 
 igt_colorop_t *igt_find_colorop(igt_display_t *display, uint32_t id);
 
-- 
2.43.0