1 files changed, 46 insertions, 9 deletions

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 5ca68aa9f237..2a00cb828d20 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -121,6 +121,22 @@ intel_dp_max_link_bw(struct intel_dp *intel_dp)
         return max_link_bw;
 }
 
+static u8 intel_dp_max_lane_count(struct intel_dp *intel_dp)
+{
+        struct intel_digital_port *intel_dig_port = dp_to_dig_port(intel_dp);
+        struct drm_device *dev = intel_dig_port->base.base.dev;
+        u8 source_max, sink_max;
+
+        source_max = 4;
+        if (HAS_DDI(dev) && intel_dig_port->port == PORT_A &&
+            (intel_dig_port->saved_port_bits & DDI_A_4_LANES) == 0)
+                source_max = 2;
+
+        sink_max = drm_dp_max_lane_count(intel_dp->dpcd);
+
+        return min(source_max, sink_max);
+}
+
 /*
  * The units on the numbers in the next two are... bizarre.  Examples will
  * make it clearer; this one parallels an example in the eDP spec.
@@ -171,7 +187,7 @@ intel_dp_mode_valid(struct drm_connector *connector,
         }
 
         max_link_clock = drm_dp_bw_code_to_link_rate(intel_dp_max_link_bw(intel_dp));
-        max_lanes = drm_dp_max_lane_count(intel_dp->dpcd);
+        max_lanes = intel_dp_max_lane_count(intel_dp);
 
         max_rate = intel_dp_max_data_rate(max_link_clock, max_lanes);
         mode_rate = intel_dp_link_required(target_clock, 18);
@@ -751,8 +767,10 @@ intel_dp_compute_config(struct intel_encoder *encoder,
         struct intel_crtc *intel_crtc = encoder->new_crtc;
         struct intel_connector *intel_connector = intel_dp->attached_connector;
         int lane_count, clock;
-        int max_lane_count = drm_dp_max_lane_count(intel_dp->dpcd);
+        int min_lane_count = 1;
+        int max_lane_count = intel_dp_max_lane_count(intel_dp);
         /* Conveniently, the link BW constants become indices with a shift...*/
+        int min_clock = 0;
         int max_clock = intel_dp_max_link_bw(intel_dp) >> 3;
         int bpp, mode_rate;
         static int bws[] = { DP_LINK_BW_1_62, DP_LINK_BW_2_7, DP_LINK_BW_5_4 };
@@ -785,19 +803,38 @@ intel_dp_compute_config(struct intel_encoder *encoder,
         /* Walk through all bpp values. Luckily they're all nicely spaced with 2
          * bpc in between. */
         bpp = pipe_config->pipe_bpp;
-        if (is_edp(intel_dp) && dev_priv->vbt.edp_bpp &&
-            dev_priv->vbt.edp_bpp < bpp) {
-                DRM_DEBUG_KMS("clamping bpp for eDP panel to BIOS-provided %i\n",
-                              dev_priv->vbt.edp_bpp);
-                bpp = dev_priv->vbt.edp_bpp;
+        if (is_edp(intel_dp)) {
+                if (dev_priv->vbt.edp_bpp && dev_priv->vbt.edp_bpp < bpp) {
+                        DRM_DEBUG_KMS("clamping bpp for eDP panel to BIOS-provided %i\n",
+                                      dev_priv->vbt.edp_bpp);
+                        bpp = dev_priv->vbt.edp_bpp;
+                }
+
+                if (IS_BROADWELL(dev)) {
+                        /* Yes, it's an ugly hack. */
+                        min_lane_count = max_lane_count;
+                        DRM_DEBUG_KMS("forcing lane count to max (%u) on BDW\n",
+                                      min_lane_count);
+                } else if (dev_priv->vbt.edp_lanes) {
+                        min_lane_count = min(dev_priv->vbt.edp_lanes,
+                                             max_lane_count);
+                        DRM_DEBUG_KMS("using min %u lanes per VBT\n",
+                                      min_lane_count);
+                }
+
+                if (dev_priv->vbt.edp_rate) {
+                        min_clock = min(dev_priv->vbt.edp_rate >> 3, max_clock);
+                        DRM_DEBUG_KMS("using min %02x link bw per VBT\n",
+                                      bws[min_clock]);
+                }
         }
 
         for (; bpp >= 6*3; bpp -= 2*3) {
                 mode_rate = intel_dp_link_required(adjusted_mode->crtc_clock,
                                                    bpp);
 
-                for (lane_count = 1; lane_count <= max_lane_count; lane_count <<= 1) {
-                        for (clock = 0; clock <= max_clock; clock++) {
+                for (lane_count = min_lane_count; lane_count <= max_lane_count; lane_count <<= 1) {
+                        for (clock = min_clock; clock <= max_clock; clock++) {
                                 link_clock = drm_dp_bw_code_to_link_rate(bws[clock]);
                                 link_avail = intel_dp_max_data_rate(link_clock,
                                                                     lane_count);