1 files changed, 72 insertions, 0 deletions
diff --git a/drivers/gpu/drm/amd/display/dc/hwss/dcn35/dcn35_hwseq.c b/drivers/gpu/drm/amd/display/dc/hwss/dcn35/dcn35_hwseq.c
index a14f99f4f14a..eb6c6ba64c0b 100644
--- a/drivers/gpu/drm/amd/display/dc/hwss/dcn35/dcn35_hwseq.c
+++ b/drivers/gpu/drm/amd/display/dc/hwss/dcn35/dcn35_hwseq.c
@@ -1373,3 +1373,75 @@ void dcn35_set_static_screen_control(struct pipe_ctx **pipe_ctx,
 			set_static_screen_control(pipe_ctx[i]->stream_res.tg,
 					triggers, params->num_frames);
 }
+
+static bool should_avoid_empty_tu(struct pipe_ctx *pipe_ctx)
+{
+	/* Calculate average pixel count per TU, return false if under ~2.00 to
+	 * avoid empty TUs. This is only required for DPIA tunneling as empty TUs
+	 * are legal to generate for native DP links. Assume TU size 64 as there
+	 * is currently no scenario where it's reprogrammed from HW default.
+	 * MTPs have no such limitation, so this does not affect MST use cases.
+	 */
+	unsigned int pix_clk_mhz;
+	unsigned int symclk_mhz;
+	unsigned int avg_pix_per_tu_x1000;
+	unsigned int tu_size_bytes = 64;
+	struct dc_crtc_timing *timing = &pipe_ctx->stream->timing;
+	struct dc_link_settings *link_settings = &pipe_ctx->link_config.dp_link_settings;
+	const struct dc *dc = pipe_ctx->stream->link->dc;
+
+	if (pipe_ctx->stream->link->ep_type != DISPLAY_ENDPOINT_USB4_DPIA)
+		return false;
+
+	// Not necessary for MST configurations
+	if (pipe_ctx->stream->signal == SIGNAL_TYPE_DISPLAY_PORT_MST)
+		return false;
+
+	pix_clk_mhz = timing->pix_clk_100hz / 10000;
+
+	// If this is true, can't block due to dynamic ODM
+	if (pix_clk_mhz > dc->clk_mgr->bw_params->clk_table.entries[0].dispclk_mhz)
+		return false;
+
+	switch (link_settings->link_rate) {
+	case LINK_RATE_LOW:
+		symclk_mhz = 162;
+		break;
+	case LINK_RATE_HIGH:
+		symclk_mhz = 270;
+		break;
+	case LINK_RATE_HIGH2:
+		symclk_mhz = 540;
+		break;
+	case LINK_RATE_HIGH3:
+		symclk_mhz = 810;
+		break;
+	default:
+		// We shouldn't be tunneling any other rates, something is wrong
+		ASSERT(0);
+		return false;
+	}
+
+	avg_pix_per_tu_x1000 = (1000 * pix_clk_mhz * tu_size_bytes)
+		/ (symclk_mhz * link_settings->lane_count);
+
+	// Add small empirically-decided margin to account for potential jitter
+	return (avg_pix_per_tu_x1000 < 2020);
+}
+
+bool dcn35_is_dp_dig_pixel_rate_div_policy(struct pipe_ctx *pipe_ctx)
+{
+	struct dc *dc = pipe_ctx->stream->ctx->dc;
+
+	if (!is_h_timing_divisible_by_2(pipe_ctx->stream))
+		return false;
+
+	if (should_avoid_empty_tu(pipe_ctx))
+		return false;
+
+	if (dc_is_dp_signal(pipe_ctx->stream->signal) && !dc->link_srv->dp_is_128b_132b_signal(pipe_ctx) &&
+		dc->debug.enable_dp_dig_pixel_rate_div_policy)
+		return true;
+
+	return false;
+}