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);