return intel_dp_common_rate(intel_dp, intel_dp->num_common_rates - 1);
 }
 
-static int intel_dp_max_source_lane_count(struct intel_digital_port *dig_port)
+int intel_dp_max_source_lane_count(struct intel_digital_port *dig_port)
 {
        int vbt_max_lanes = intel_bios_dp_max_lane_count(dig_port->base.devdata);
        int max_lanes = dig_port->max_lanes;
        return min3(source_max, sink_max, lane_max);
 }
 
+static int forced_lane_count(struct intel_dp *intel_dp)
+{
+       return clamp(intel_dp->link.force_lane_count, 1, intel_dp_max_common_lane_count(intel_dp));
+}
+
 int intel_dp_max_lane_count(struct intel_dp *intel_dp)
 {
-       switch (intel_dp->link.max_lane_count) {
+       int lane_count;
+
+       if (intel_dp->link.force_lane_count)
+               lane_count = forced_lane_count(intel_dp);
+       else
+               lane_count = intel_dp->link.max_lane_count;
+
+       switch (lane_count) {
        case 1:
        case 2:
        case 4:
-               return intel_dp->link.max_lane_count;
+               return lane_count;
        default:
-               MISSING_CASE(intel_dp->link.max_lane_count);
+               MISSING_CASE(lane_count);
                return 1;
        }
 }
 
+static int intel_dp_min_lane_count(struct intel_dp *intel_dp)
+{
+       if (intel_dp->link.force_lane_count)
+               return forced_lane_count(intel_dp);
+
+       return 1;
+}
+
 /*
  * The required data bandwidth for a mode with given pixel clock and bpp. This
  * is the required net bandwidth independent of the data bandwidth efficiency.
        drm_dbg_kms(&i915->drm, "common rates: %s\n", str);
 }
 
+static int forced_link_rate(struct intel_dp *intel_dp)
+{
+       int len = intel_dp_common_len_rate_limit(intel_dp, intel_dp->link.force_rate);
+
+       if (len == 0)
+               return intel_dp_common_rate(intel_dp, 0);
+
+       return intel_dp_common_rate(intel_dp, len - 1);
+}
+
 int
 intel_dp_max_link_rate(struct intel_dp *intel_dp)
 {
        int len;
 
+       if (intel_dp->link.force_rate)
+               return forced_link_rate(intel_dp);
+
        len = intel_dp_common_len_rate_limit(intel_dp, intel_dp->link.max_rate);
 
        return intel_dp_common_rate(intel_dp, len - 1);
 }
 
+static int
+intel_dp_min_link_rate(struct intel_dp *intel_dp)
+{
+       if (intel_dp->link.force_rate)
+               return forced_link_rate(intel_dp);
+
+       return intel_dp_common_rate(intel_dp, 0);
+}
+
 int intel_dp_rate_select(struct intel_dp *intel_dp, int rate)
 {
        struct drm_i915_private *i915 = dp_to_i915(intel_dp);
                               bool dsc,
                               struct link_config_limits *limits)
 {
-       limits->min_rate = intel_dp_common_rate(intel_dp, 0);
+       limits->min_rate = intel_dp_min_link_rate(intel_dp);
        limits->max_rate = intel_dp_max_link_rate(intel_dp);
 
        /* FIXME 128b/132b SST support missing */
        limits->max_rate = min(limits->max_rate, 810000);
+       limits->min_rate = min(limits->min_rate, limits->max_rate);
 
-       limits->min_lane_count = 1;
+       limits->min_lane_count = intel_dp_min_lane_count(intel_dp);
        limits->max_lane_count = intel_dp_max_lane_count(intel_dp);
 
        limits->pipe.min_bpp = intel_dp_min_bpp(crtc_state->output_format);
        intel_dp->lane_count = lane_count;
 }
 
-static void intel_dp_reset_link_params(struct intel_dp *intel_dp)
+void intel_dp_reset_link_params(struct intel_dp *intel_dp)
 {
        intel_dp->link.max_lane_count = intel_dp_max_common_lane_count(intel_dp);
        intel_dp->link.max_rate = intel_dp_max_common_rate(intel_dp);
 
        int rate_index;
        int new_rate;
 
+       if (intel_dp->link.force_rate)
+               return -1;
+
        rate_index = intel_dp_rate_index(intel_dp->common_rates,
                                         intel_dp->num_common_rates,
                                         current_rate);
 
 static int reduce_lane_count(struct intel_dp *intel_dp, int current_lane_count)
 {
+       if (intel_dp->link.force_lane_count)
+               return -1;
+
        if (current_lane_count == 1)
                return -1;
 
 
        lt_dbg(intel_dp, DP_PHY_DPRX, "DP2.0 SDP CRC16 for 128b/132b enabled\n");
 }
+
+static struct intel_dp *intel_connector_to_intel_dp(struct intel_connector *connector)
+{
+       if (connector->mst_port)
+               return connector->mst_port;
+       else
+               return enc_to_intel_dp(intel_attached_encoder(connector));
+}
+
+static int i915_dp_force_link_rate_show(struct seq_file *m, void *data)
+{
+       struct intel_connector *connector = to_intel_connector(m->private);
+       struct drm_i915_private *i915 = to_i915(connector->base.dev);
+       struct intel_dp *intel_dp = intel_connector_to_intel_dp(connector);
+       int current_rate = -1;
+       int force_rate;
+       int err;
+       int i;
+
+       err = drm_modeset_lock_single_interruptible(&i915->drm.mode_config.connection_mutex);
+       if (err)
+               return err;
+
+       if (intel_dp->link_trained)
+               current_rate = intel_dp->link_rate;
+       force_rate = intel_dp->link.force_rate;
+
+       drm_modeset_unlock(&i915->drm.mode_config.connection_mutex);
+
+       seq_printf(m, "%sauto%s",
+                  force_rate == 0 ? "[" : "",
+                  force_rate == 0 ? "]" : "");
+
+       for (i = 0; i < intel_dp->num_source_rates; i++)
+               seq_printf(m, " %s%d%s%s",
+                          intel_dp->source_rates[i] == force_rate ? "[" : "",
+                          intel_dp->source_rates[i],
+                          intel_dp->source_rates[i] == current_rate ? "*" : "",
+                          intel_dp->source_rates[i] == force_rate ? "]" : "");
+
+       seq_putc(m, '\n');
+
+       return 0;
+}
+
+static int parse_link_rate(struct intel_dp *intel_dp, const char __user *ubuf, size_t len)
+{
+       char *kbuf;
+       const char *p;
+       int rate;
+       int ret = 0;
+
+       kbuf = memdup_user_nul(ubuf, len);
+       if (IS_ERR(kbuf))
+               return PTR_ERR(kbuf);
+
+       p = strim(kbuf);
+
+       if (!strcmp(p, "auto")) {
+               rate = 0;
+       } else {
+               ret = kstrtoint(p, 0, &rate);
+               if (ret < 0)
+                       goto out_free;
+
+               if (intel_dp_rate_index(intel_dp->source_rates,
+                                       intel_dp->num_source_rates,
+                                       rate) < 0)
+                       ret = -EINVAL;
+       }
+
+out_free:
+       kfree(kbuf);
+
+       return ret < 0 ? ret : rate;
+}
+
+static ssize_t i915_dp_force_link_rate_write(struct file *file,
+                                            const char __user *ubuf,
+                                            size_t len, loff_t *offp)
+{
+       struct seq_file *m = file->private_data;
+       struct intel_connector *connector = to_intel_connector(m->private);
+       struct drm_i915_private *i915 = to_i915(connector->base.dev);
+       struct intel_dp *intel_dp = intel_connector_to_intel_dp(connector);
+       int rate;
+       int err;
+
+       rate = parse_link_rate(intel_dp, ubuf, len);
+       if (rate < 0)
+               return rate;
+
+       err = drm_modeset_lock_single_interruptible(&i915->drm.mode_config.connection_mutex);
+       if (err)
+               return err;
+
+       intel_dp_reset_link_params(intel_dp);
+       intel_dp->link.force_rate = rate;
+
+       drm_modeset_unlock(&i915->drm.mode_config.connection_mutex);
+
+       *offp += len;
+
+       return len;
+}
+DEFINE_SHOW_STORE_ATTRIBUTE(i915_dp_force_link_rate);
+
+static int i915_dp_force_lane_count_show(struct seq_file *m, void *data)
+{
+       struct intel_connector *connector = to_intel_connector(m->private);
+       struct drm_i915_private *i915 = to_i915(connector->base.dev);
+       struct intel_dp *intel_dp = intel_connector_to_intel_dp(connector);
+       int current_lane_count = -1;
+       int force_lane_count;
+       int err;
+       int i;
+
+       err = drm_modeset_lock_single_interruptible(&i915->drm.mode_config.connection_mutex);
+       if (err)
+               return err;
+
+       if (intel_dp->link_trained)
+               current_lane_count = intel_dp->lane_count;
+       force_lane_count = intel_dp->link.force_lane_count;
+
+       drm_modeset_unlock(&i915->drm.mode_config.connection_mutex);
+
+       seq_printf(m, "%sauto%s",
+                  force_lane_count == 0 ? "[" : "",
+                  force_lane_count == 0 ? "]" : "");
+
+       for (i = 1; i <= 4; i <<= 1)
+               seq_printf(m, " %s%d%s%s",
+                          i == force_lane_count ? "[" : "",
+                          i,
+                          i == current_lane_count ? "*" : "",
+                          i == force_lane_count ? "]" : "");
+
+       seq_putc(m, '\n');
+
+       return 0;
+}
+
+static int parse_lane_count(const char __user *ubuf, size_t len)
+{
+       char *kbuf;
+       const char *p;
+       int lane_count;
+       int ret = 0;
+
+       kbuf = memdup_user_nul(ubuf, len);
+       if (IS_ERR(kbuf))
+               return PTR_ERR(kbuf);
+
+       p = strim(kbuf);
+
+       if (!strcmp(p, "auto")) {
+               lane_count = 0;
+       } else {
+               ret = kstrtoint(p, 0, &lane_count);
+               if (ret < 0)
+                       goto out_free;
+
+               switch (lane_count) {
+               case 1:
+               case 2:
+               case 4:
+                       break;
+               default:
+                       ret = -EINVAL;
+               }
+       }
+
+out_free:
+       kfree(kbuf);
+
+       return ret < 0 ? ret : lane_count;
+}
+
+static ssize_t i915_dp_force_lane_count_write(struct file *file,
+                                             const char __user *ubuf,
+                                             size_t len, loff_t *offp)
+{
+       struct seq_file *m = file->private_data;
+       struct intel_connector *connector = to_intel_connector(m->private);
+       struct drm_i915_private *i915 = to_i915(connector->base.dev);
+       struct intel_dp *intel_dp = intel_connector_to_intel_dp(connector);
+       int lane_count;
+       int err;
+
+       lane_count = parse_lane_count(ubuf, len);
+       if (lane_count < 0)
+               return lane_count;
+
+       err = drm_modeset_lock_single_interruptible(&i915->drm.mode_config.connection_mutex);
+       if (err)
+               return err;
+
+       intel_dp_reset_link_params(intel_dp);
+       intel_dp->link.force_lane_count = lane_count;
+
+       drm_modeset_unlock(&i915->drm.mode_config.connection_mutex);
+
+       *offp += len;
+
+       return len;
+}
+DEFINE_SHOW_STORE_ATTRIBUTE(i915_dp_force_lane_count);
+
+void intel_dp_link_training_debugfs_add(struct intel_connector *connector)
+{
+       struct dentry *root = connector->base.debugfs_entry;
+
+       if (connector->base.connector_type != DRM_MODE_CONNECTOR_DisplayPort &&
+           connector->base.connector_type != DRM_MODE_CONNECTOR_eDP)
+               return;
+
+       debugfs_create_file("i915_dp_force_link_rate", 0644, root,
+                           connector, &i915_dp_force_link_rate_fops);
+
+       debugfs_create_file("i915_dp_force_lane_count", 0644, root,
+                           connector, &i915_dp_force_lane_count_fops);
+}