drm/amd/display: Fix a few parts in debugfs entry

[Why & How]
1. To leverage and simplify the igt tool. Change the value of
retrain when calling preferred training settings.
Now, writing value to link settings triggers link training immediately.

2. Add dc lock when triggering link training in edp_ilr_write()
Reviewed-by: NRodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Acked-by: NAgustin Gutierrez <agustin.gutierrez@amd.com>
Signed-off-by: NWayne Lin <Wayne.Lin@amd.com>
Tested-by: NDaniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_debugfs.c

@@ -243,6 +243,7 @@ static ssize_t dp_link_settings_write(struct file *f, const char __user *buf,
 {
 	struct amdgpu_dm_connector *connector = file_inode(f)->i_private;
 	struct dc_link *link = connector->dc_link;
+	struct amdgpu_device *adev = drm_to_adev(connector->base.dev);
 	struct dc *dc = (struct dc *)link->dc;
 	struct dc_link_settings prefer_link_settings;
 	char *wr_buf = NULL;
@@ -302,6 +303,9 @@ static ssize_t dp_link_settings_write(struct file *f, const char __user *buf,
 	if (!valid_input) {
 		kfree(wr_buf);
 		DRM_DEBUG_DRIVER("Invalid Input value No HW will be programmed\n");
+		mutex_lock(&adev->dm.dc_lock);
+		dc_link_set_preferred_training_settings(dc, NULL, NULL, link, false);
+		mutex_unlock(&adev->dm.dc_lock);
 		return size;
 	}
 
@@ -313,7 +317,9 @@ static ssize_t dp_link_settings_write(struct file *f, const char __user *buf,
 	prefer_link_settings.lane_count = param[0];
 	prefer_link_settings.link_rate = param[1];
 
-	dc_link_set_preferred_training_settings(dc, &prefer_link_settings, NULL, link, true);
+	mutex_lock(&adev->dm.dc_lock);
+	dc_link_set_preferred_training_settings(dc, &prefer_link_settings, NULL, link, false);
+	mutex_unlock(&adev->dm.dc_lock);
 
 	kfree(wr_buf);
 	return size;
@@ -2883,7 +2889,9 @@ static ssize_t edp_ilr_write(struct file *f, const char __user *buf,
 		kfree(wr_buf);
 		DRM_DEBUG_DRIVER("Invalid Input value. No HW will be programmed\n");
 		prefer_link_settings.use_link_rate_set = false;
+		mutex_lock(&adev->dm.dc_lock);
 		dc_link_set_preferred_training_settings(dc, NULL, NULL, link, false);
+		mutex_unlock(&adev->dm.dc_lock);
 		return size;
 	}