drm/amd/display: Revert "Directly retrain link from debugfs"

commit 1131cad upstream.

This reverts commit f5b6a20.

This patch broke new settings from taking effect. Hotplug is
required for new settings to take effect.

Reviewed-by: Mikita Lipski <mikita.lipski@amd.com>
Acked-by: Mikita Lipski <mikita.lipski@amd.com>
Signed-off-by: Anson Jacob <Anson.Jacob@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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

@@ -247,6 +247,7 @@ 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 dc *dc = (struct dc *)link->dc;
 	struct dc_link_settings prefer_link_settings;
 	char *wr_buf = NULL;
 	const uint32_t wr_buf_size = 40;
@@ -313,7 +314,7 @@ 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];
 
-	dp_retrain_link_dp_test(link, &prefer_link_settings, false);
+	dc_link_set_preferred_training_settings(dc, &prefer_link_settings, NULL, link, true);
 
 	kfree(wr_buf);
 	return size;