Fix possible_clones computation for shared encoders between outputs

Libdrm's possible_clones is a mask of encoders. Xorg's possible_clones
is a mask of outputs, so we just can't do the following:

  output->possible_clones = kencoder->possible_clones;

This is a problem on Haswell because, at least with the current
patches floating on the mailing list, there is more than one connector
per encoder.

This patch writes the code to properly translate libdrm's encoder mask
into Xorg's output mask.

Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

src/intel_display.c

@@ -1435,7 +1435,6 @@ intel_output_init(ScrnInfoPtr scrn, struct intel_mode *mode, int num)
 		intel_output_backlight_init(output);
 
 	output->possible_crtcs = kencoder->possible_crtcs;
-	output->possible_clones = kencoder->possible_clones;
 	output->interlaceAllowed = TRUE;
 
 	intel_output->output = output;
@@ -1680,6 +1679,60 @@ drm_wakeup_handler(pointer data, int err, pointer p)
 		drmHandleEvent(mode->fd, &mode->event_context);
 }
 
+static drmModeEncoderPtr
+intel_get_kencoder(struct intel_mode *mode, int num)
+{
+	struct intel_output *iterator;
+	int id = mode->mode_res->encoders[num];
+
+	list_for_each_entry(iterator, &mode->outputs, link)
+		if (iterator->mode_encoder->encoder_id == id)
+			return iterator->mode_encoder;
+
+	return NULL;
+}
+
+/*
+ * Libdrm's possible_clones is a mask of encoders, Xorg's possible_clones is a
+ * mask of outputs. This function sets Xorg's possible_clones based on the
+ * values read from libdrm.
+ */
+static void
+intel_compute_possible_clones(ScrnInfoPtr scrn, struct intel_mode *mode)
+{
+	xf86CrtcConfigPtr config = XF86_CRTC_CONFIG_PTR(scrn);
+	struct intel_output *intel_output, *clone;
+	drmModeEncoderPtr cloned_encoder;
+	uint32_t mask;
+	int i, j, k;
+	CARD32 possible_clones;
+
+	for (i = 0; i < config->num_output; i++) {
+		possible_clones = 0;
+		intel_output = config->output[i]->driver_private;
+
+		mask = intel_output->mode_encoder->possible_clones;
+		for (j = 0; mask != 0; j++, mask >>= 1) {
+
+			if ((mask & 1) == 0)
+				continue;
+
+			cloned_encoder = intel_get_kencoder(mode, j);
+			if (!cloned_encoder)
+				continue;
+
+			for (k = 0; k < config->num_output; k++) {
+				clone = config->output[k]->driver_private;
+				if (clone->mode_encoder->encoder_id ==
+				    cloned_encoder->encoder_id)
+					possible_clones |= (1 << k);
+			}
+		}
+
+		config->output[i]->possible_clones = possible_clones;
+	}
+}
+
 Bool intel_mode_pre_init(ScrnInfoPtr scrn, int fd, int cpp)
 {
 	intel_screen_private *intel = intel_get_screen_private(scrn);
@@ -1716,6 +1769,8 @@ Bool intel_mode_pre_init(ScrnInfoPtr scrn, int fd, int cpp)
 	for (i = 0; i < mode->mode_res->count_connectors; i++)
 		intel_output_init(scrn, mode, i);
 
+	intel_compute_possible_clones(scrn, mode);
+
 #ifdef INTEL_PIXMAP_SHARING
 	xf86ProviderSetup(scrn, NULL, "Intel");
 #endif

src/sna/sna_display.c

@@ -2291,6 +2291,35 @@ cleanup_connector:
 	drmModeFreeConnector(koutput);
 }
 
+/* The kernel reports possible encoder clones, whereas X uses a list of
+ * possible connector clones. This is works when we have a 1:1 mapping
+ * between encoders and connectors, but breaks for Haswell which has a pair
+ * of DP/HDMI connectors hanging off a single encoder.
+ */
+static void
+sna_mode_compute_possible_clones(ScrnInfoPtr scrn)
+{
+	xf86CrtcConfigPtr config = XF86_CRTC_CONFIG_PTR(scrn);
+	unsigned clones[32] = { 0 };
+	int i, j;
+
+	assert(config->num_output <= 32);
+
+	/* Convert from encoder numbering to output numbering */
+	for (i = 0; i < config->num_output; i++) {
+		unsigned mask = config->output[i]->possible_clones;
+		for (j = 0; mask != 0; j++, mask >>= 1) {
+			if ((mask & 1) == 0)
+				continue;
+
+			clones[j] |= 1 << i;
+		}
+	}
+
+	for (i = 0; i < config->num_output; i++)
+		config->output[i]->possible_clones = clones[i];
+}
+
 struct sna_visit_set_pixmap_window {
 	PixmapPtr old, new;
 };
@@ -2574,6 +2603,9 @@ bool sna_mode_pre_init(ScrnInfoPtr scrn, struct sna *sna)
 	for (i = 0; i < mode->kmode->count_connectors; i++)
 		sna_output_init(scrn, mode, i);
 
+	if (!xf86IsEntityShared(scrn->entityList[0]))
+		sna_mode_compute_possible_clones(scrn);
+
 #if HAS_PIXMAP_SHARING
 	xf86ProviderSetup(scrn, NULL, "Intel");
 #endif