drm/amd/display: Setup stream encoder before link enable for TMDS

[Why]
HDMI spec requires TMDS clock to be not more than 340MHz. Stream encoder ensure
this requirement but driver enable stream encoder later than PHY. So PHY will
output full speed TMDS clock first.

[How]
Enable stream encoder first in TMDS case.

Reviewed-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Acked-by: Alan Liu <haoping.liu@amd.com>
Signed-off-by: JinZe Xu <jinze.xu@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/link/link_dpms.c

@@ -1971,6 +1971,7 @@ static void enable_link_hdmi(struct pipe_ctx *pipe_ctx)
 	bool is_vga_mode = (stream->timing.h_addressable == 640)
 			&& (stream->timing.v_addressable == 480);
 	struct dc *dc = pipe_ctx->stream->ctx->dc;
+	const struct link_hwss *link_hwss = get_link_hwss(link, &pipe_ctx->link_res);
 
 	if (stream->phy_pix_clk == 0)
 		stream->phy_pix_clk = stream->timing.pix_clk_100hz / 10;
@@ -2010,6 +2011,12 @@ static void enable_link_hdmi(struct pipe_ctx *pipe_ctx)
 	if (stream->timing.pixel_encoding == PIXEL_ENCODING_YCBCR422)
 		display_color_depth = COLOR_DEPTH_888;
 
+	/* We need to enable stream encoder for TMDS first to apply 1/4 TMDS
+	 * character clock in case that beyond 340MHz.
+	 */
+	if (dc_is_hdmi_tmds_signal(pipe_ctx->stream->signal))
+		link_hwss->setup_stream_encoder(pipe_ctx);
+
 	dc->hwss.enable_tmds_link_output(
 			link,
 			&pipe_ctx->link_res,