drm/amd/display: do not copy invalid CRTC timing info

Since b255ce4, it is possible that the CRTC timing
information for the preferred mode has not yet been
calculated while amdgpu_dm_connector_mode_valid() is running.

In this case use the CRTC timing information of the actual mode.

Fixes: b255ce4 ("drm/amdgpu: don't change mode in amdgpu_dm_connector_mode_valid()")
Closes: https://lore.kernel.org/all/ed09edb167e74167a694f4854102a3de6d2f1433.camel@irl.hu/
Closes: https://gitlab.freedesktop.org/drm/amd/-/issues/4085
Signed-off-by: Gergo Koteles <soyer@irl.hu>
Reviewed-by: Zaeem Mohamed <zaeem.mohamed@amd.com>
Tested-by: Mark Broadworth <mark.broadworth@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 2023219)
Cc: stable@vger.kernel.org

Author: soyersoyer

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

@@ -6501,12 +6501,12 @@ decide_crtc_timing_for_drm_display_mode(struct drm_display_mode *drm_mode,
 					const struct drm_display_mode *native_mode,
 					bool scale_enabled)
 {
-	if (scale_enabled) {
-		copy_crtc_timing_for_drm_display_mode(native_mode, drm_mode);
-	} else if (native_mode->clock == drm_mode->clock &&
-			native_mode->htotal == drm_mode->htotal &&
-			native_mode->vtotal == drm_mode->vtotal) {
-		copy_crtc_timing_for_drm_display_mode(native_mode, drm_mode);
+	if (scale_enabled || (
+	    native_mode->clock == drm_mode->clock &&
+	    native_mode->htotal == drm_mode->htotal &&
+	    native_mode->vtotal == drm_mode->vtotal)) {
+		if (native_mode->crtc_clock)
+			copy_crtc_timing_for_drm_display_mode(native_mode, drm_mode);
 	} else {
 		/* no scaling nor amdgpu inserted, no need to patch */
 	}