drm/amd/display: Use DTO as clock on DP if not

Use DVO as pixel clock for DP before enabling link
PHY. Otherwise, when switching from HDMI passive dongle
to DP on the same connector, the PHY PLL is used as
pixel clock, and CRTC would stop working.
Signed-off-by: Ding Wang <Ding.Wang@amd.com>
Reviewed-by: Tony Cheng <Tony.Cheng@amd.com>
Acked-by: Harry Wentland <Harry.Wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/core/dc_link_hwss.c

@@ -61,6 +61,31 @@ void dp_enable_link_phy(
 {
 	struct link_encoder *link_enc = link->link_enc;
 
+	struct pipe_ctx *pipes =
+			link->dc->current_context->res_ctx.pipe_ctx;
+	struct clock_source *dp_cs =
+			link->dc->res_pool->dp_clock_source;
+	unsigned int i;
+	/* If the current pixel clock source is not DTO(happens after
+	 * switching from HDMI passive dongle to DP on the same connector),
+	 * switch the pixel clock source to DTO.
+	 */
+	for (i = 0; i < MAX_PIPES; i++) {
+		if (pipes[i].stream != NULL &&
+			pipes[i].stream->sink != NULL &&
+			pipes[i].stream->sink->link == link) {
+			if (pipes[i].clock_source->id != CLOCK_SOURCE_ID_DP_DTO) {
+				pipes[i].clock_source = dp_cs;
+				pipes[i].pix_clk_params.requested_pix_clk =
+						pipes[i].stream->public.timing.pix_clk_khz;
+				pipes[i].clock_source->funcs->program_pix_clk(
+							pipes[i].clock_source,
+							&pipes[i].pix_clk_params,
+							&pipes[i].pll_settings);
+			}
+		}
+	}
+
 	if (dc_is_dp_sst_signal(signal)) {
 		if (signal == SIGNAL_TYPE_EDP) {
 			link_enc->funcs->power_control(link_enc, true);