drm/fbdev: fix cloning on fbcon

Simple cloning rules compared to server:
(a) single crtc
(b) > 1 connector active
(c) check command line mode
(d) try and find 1024x768 DMT mode if no command line.
(e) fail to clone

Signed-off-by: Dave Airlie <airlied@redhat.com>

1 files changed, 85 insertions, 5 deletions

diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
index f7b8fca4bbbc..b3779d243aef 100644
--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -1070,6 +1070,79 @@ static void drm_enable_connectors(struct drm_fb_helper *fb_helper,
 	}
 }
 
+static bool drm_target_cloned(struct drm_fb_helper *fb_helper,
+			      struct drm_display_mode **modes,
+			      bool *enabled, int width, int height)
+{
+	int count, i, j;
+	bool can_clone = false;
+	struct drm_fb_helper_connector *fb_helper_conn;
+	struct drm_display_mode *dmt_mode, *mode;
+
+	/* only contemplate cloning in the single crtc case */
+	if (fb_helper->crtc_count > 1)
+		return false;
+
+	count = 0;
+	for (i = 0; i < fb_helper->connector_count; i++) {
+		if (enabled[i])
+			count++;
+	}
+
+	/* only contemplate cloning if more than one connector is enabled */
+	if (count <= 1)
+		return false;
+
+	/* check the command line or if nothing common pick 1024x768 */
+	can_clone = true;
+	for (i = 0; i < fb_helper->connector_count; i++) {
+		if (!enabled[i])
+			continue;
+		fb_helper_conn = fb_helper->connector_info[i];
+		modes[i] = drm_pick_cmdline_mode(fb_helper_conn, width, height);
+		if (!modes[i]) {
+			can_clone = false;
+			break;
+		}
+		for (j = 0; j < i; j++) {
+			if (!enabled[j])
+				continue;
+			if (!drm_mode_equal(modes[j], modes[i]))
+				can_clone = false;
+		}
+	}
+
+	if (can_clone) {
+		DRM_DEBUG_KMS("can clone using command line\n");
+		return true;
+	}
+
+	/* try and find a 1024x768 mode on each connector */
+	can_clone = true;
+	dmt_mode = drm_mode_find_dmt(fb_helper->dev, 1024, 768, 60);
+
+	for (i = 0; i < fb_helper->connector_count; i++) {
+
+		if (!enabled[i])
+			continue;
+
+		fb_helper_conn = fb_helper->connector_info[i];
+		list_for_each_entry(mode, &fb_helper_conn->connector->modes, head) {
+			if (drm_mode_equal(mode, dmt_mode))
+				modes[i] = mode;
+		}
+		if (!modes[i])
+			can_clone = false;
+	}
+
+	if (can_clone) {
+		DRM_DEBUG_KMS("can clone using 1024x768\n");
+		return true;
+	}
+	DRM_INFO("kms: can't enable cloning when we probably wanted to.\n");
+	return false;
+}
+
 static bool drm_target_preferred(struct drm_fb_helper *fb_helper,
 				 struct drm_display_mode **modes,
 				 bool *enabled, int width, int height)
@@ -1163,8 +1236,12 @@ static int drm_pick_crtcs(struct drm_fb_helper *fb_helper,
 				break;
 
 		if (o < n) {
-			/* ignore cloning for now */
-			continue;
+			/* ignore cloning unless only a single crtc */
+			if (fb_helper->crtc_count > 1)
+				continue;
+
+			if (!drm_mode_equal(modes[o], modes[n]))
+				continue;
 		}
 
 		crtcs[n] = crtc;
@@ -1214,9 +1291,12 @@ static void drm_setup_crtcs(struct drm_fb_helper *fb_helper)
 
 	drm_enable_connectors(fb_helper, enabled);
 
-	ret = drm_target_preferred(fb_helper, modes, enabled, width, height);
-	if (!ret)
-		DRM_ERROR("Unable to find initial modes\n");
+	ret = drm_target_cloned(fb_helper, modes, enabled, width, height);
+	if (!ret) {
+		ret = drm_target_preferred(fb_helper, modes, enabled, width, height);
+		if (!ret)
+			DRM_ERROR("Unable to find initial modes\n");
+	}
 
 	DRM_DEBUG_KMS("picking CRTCs for %dx%d config\n", width, height);