drm/amd/display: Add Underflow Asserts to dc

[Why]
For debugging underflow issues it can be useful to have asserts when the
underflow initially occurs.

[How]
Read the underflow status registers after actions that have a high risk
of causing underflow and assert that no underflow occurred. If underflow
occurred, clear the bit.

Signed-off-by: Thomas Lim <Thomas.Lim@amd.com>
Reviewed-by: Eric Yang <eric.yang2@amd.com>
Acked-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/dc.h

@@ -329,6 +329,7 @@ struct dc_debug_options {
 	int sr_exit_time_ns;
 	int sr_enter_plus_exit_time_ns;
 	int urgent_latency_ns;
+	uint32_t underflow_assert_delay_us;
 	int percent_of_ideal_drambw;
 	int dram_clock_change_latency_ns;
 	bool optimized_watermark;

drivers/gpu/drm/amd/display/dc/dcn10/dcn10_hw_sequencer.c

@@ -360,6 +360,23 @@ void dcn10_log_hw_state(struct dc *dc,
 	DTN_INFO_END();
 }
 
+bool dcn10_did_underflow_occur(struct dc *dc, struct pipe_ctx *pipe_ctx)
+{
+	struct hubp *hubp = pipe_ctx->plane_res.hubp;
+	struct timing_generator *tg = pipe_ctx->stream_res.tg;
+
+	if (tg->funcs->is_optc_underflow_occurred(tg)) {
+		tg->funcs->clear_optc_underflow(tg);
+		return true;
+	}
+
+	if (hubp->funcs->hubp_get_underflow_status(hubp)) {
+		hubp->funcs->hubp_clear_underflow(hubp);
+		return true;
+	}
+	return false;
+}
+
 static void enable_power_gating_plane(
 	struct dce_hwseq *hws,
 	bool enable)
@@ -2332,6 +2349,7 @@ static void dcn10_apply_ctx_for_surface(
 {
 	int i;
 	struct timing_generator *tg;
+	uint32_t underflow_check_delay_us;
 	bool removed_pipe[4] = { false };
 	bool interdependent_update = false;
 	struct pipe_ctx *top_pipe_to_program =
@@ -2346,11 +2364,22 @@ static void dcn10_apply_ctx_for_surface(
 	interdependent_update = top_pipe_to_program->plane_state &&
 		top_pipe_to_program->plane_state->update_flags.bits.full_update;
 
+	underflow_check_delay_us = dc->debug.underflow_assert_delay_us;
+
+	if (underflow_check_delay_us != 0xFFFFFFFF && dc->hwss.did_underflow_occur)
+		ASSERT(dc->hwss.did_underflow_occur(dc, top_pipe_to_program));
+
 	if (interdependent_update)
 		lock_all_pipes(dc, context, true);
 	else
 		dcn10_pipe_control_lock(dc, top_pipe_to_program, true);
 
+	if (underflow_check_delay_us != 0xFFFFFFFF)
+		udelay(underflow_check_delay_us);
+
+	if (underflow_check_delay_us != 0xFFFFFFFF && dc->hwss.did_underflow_occur)
+		ASSERT(dc->hwss.did_underflow_occur(dc, top_pipe_to_program));
+
 	if (num_planes == 0) {
 		/* OTG blank before remove all front end */
 		dc->hwss.blank_pixel_data(dc, top_pipe_to_program, true);
@@ -3022,7 +3051,8 @@ static const struct hw_sequencer_funcs dcn10_funcs = {
 	.disable_stream_gating = NULL,
 	.enable_stream_gating = NULL,
 	.setup_periodic_interrupt = dcn10_setup_periodic_interrupt,
-	.setup_vupdate_interrupt = dcn10_setup_vupdate_interrupt
+	.setup_vupdate_interrupt = dcn10_setup_vupdate_interrupt,
+	.did_underflow_occur = dcn10_did_underflow_occur
 };
 
 

drivers/gpu/drm/amd/display/dc/dcn10/dcn10_hw_sequencer.h

@@ -71,6 +71,8 @@ void dcn10_get_hdr_visual_confirm_color(
 		struct pipe_ctx *pipe_ctx,
 		struct tg_color *color);
 
+bool dcn10_did_underflow_occur(struct dc *dc, struct pipe_ctx *pipe_ctx);
+
 void update_dchubp_dpp(
 	struct dc *dc,
 	struct pipe_ctx *pipe_ctx,

drivers/gpu/drm/amd/display/dc/dcn10/dcn10_resource.c

@@ -560,6 +560,7 @@ static const struct dc_debug_options debug_defaults_drv = {
 		.az_endpoint_mute_only = true,
 		.recovery_enabled = false, /*enable this by default after testing.*/
 		.max_downscale_src_width = 3840,
+		.underflow_assert_delay_us = 0xFFFFFFFF,
 };
 
 static const struct dc_debug_options debug_defaults_diags = {
@@ -569,7 +570,8 @@ static const struct dc_debug_options debug_defaults_diags = {
 		.clock_trace = true,
 		.disable_stutter = true,
 		.disable_pplib_clock_request = true,
-		.disable_pplib_wm_range = true
+		.disable_pplib_wm_range = true,
+		.underflow_assert_delay_us = 0xFFFFFFFF,
 };
 
 static void dcn10_dpp_destroy(struct dpp **dpp)

drivers/gpu/drm/amd/display/dc/inc/hw_sequencer.h

@@ -240,6 +240,7 @@ struct hw_sequencer_funcs {
 
 	void (*setup_periodic_interrupt)(struct pipe_ctx *pipe_ctx, enum vline_select vline);
 	void (*setup_vupdate_interrupt)(struct pipe_ctx *pipe_ctx);
+	bool (*did_underflow_occur)(struct dc *dc, struct pipe_ctx *pipe_ctx);
 
 };