drm/amd/display: Add workaround to restrict max frac urgent for DPM0

[WHY]
Underflow occurs on some platforms when urgent BW is close to
the maximum in DPM0.

[HOW]
It does not occur at DPM1, so as a workaround restrict the maximum
amount and increase the lowest state index for clock states until
we're out of DPM0.
Adds DML2 config options to specify this pe platform as required.

Reviewed-by: Nicholas Kazlauskas <[email protected]>
Signed-off-by: Alex Hung <[email protected]>
Signed-off-by: Sung-huai Wang <[email protected]>
Tested-by: Daniel Wheeler <[email protected]>
Signed-off-by: Alex Deucher <[email protected]>

3 files changed, 19 insertions, 1 deletions

diff --git a/drivers/gpu/drm/amd/display/dc/dml2/dml2_wrapper.c b/drivers/gpu/drm/amd/display/dc/dml2/dml2_wrapper.c
index f6310408dbba..f4038ac2e476 100644
--- a/drivers/gpu/drm/amd/display/dc/dml2/dml2_wrapper.c
+++ b/drivers/gpu/drm/amd/display/dc/dml2/dml2_wrapper.c
@@ -628,6 +628,21 @@ static bool dml2_validate_and_build_resource(const struct dc *in_dc, struct dc_s
 
 	if (result) {
 		unsigned int lowest_state_idx = s->mode_support_params.out_lowest_state_idx;
+		double min_fclk_mhz_for_urgent_workaround = (double)dml2->config.min_fclk_for_urgent_workaround_khz / 1000.0;
+		double max_frac_urgent = (double)dml2->config.max_frac_urgent_for_min_fclk_x1000 / 1000.0;
+
+		if (min_fclk_mhz_for_urgent_workaround > 0.0 && max_frac_urgent > 0.0 &&
+		    (dml2->v20.dml_core_ctx.mp.FractionOfUrgentBandwidth > max_frac_urgent ||
+		     dml2->v20.dml_core_ctx.mp.FractionOfUrgentBandwidthImmediateFlip > max_frac_urgent)) {
+			unsigned int forced_lowest_state_idx = lowest_state_idx;
+
+			while (forced_lowest_state_idx < dml2->v20.dml_core_ctx.states.num_states &&
+			       dml2->v20.dml_core_ctx.states.state_array[forced_lowest_state_idx].fabricclk_mhz <= min_fclk_mhz_for_urgent_workaround) {
+				forced_lowest_state_idx += 1;
+			}
+			lowest_state_idx = forced_lowest_state_idx;
+		}
+
 		out_clks.dispclk_khz = (unsigned int)dml2->v20.dml_core_ctx.mp.Dispclk_calculated * 1000;
 		out_clks.p_state_supported = s->mode_support_info.DRAMClockChangeSupport[0] != dml_dram_clock_change_unsupported;
 		if (in_dc->config.use_default_clock_table &&
diff --git a/drivers/gpu/drm/amd/display/dc/dml2/dml2_wrapper.h b/drivers/gpu/drm/amd/display/dc/dml2/dml2_wrapper.h
index 20b3970c0857..79bf2d757804 100644
--- a/drivers/gpu/drm/amd/display/dc/dml2/dml2_wrapper.h
+++ b/drivers/gpu/drm/amd/display/dc/dml2/dml2_wrapper.h
@@ -237,6 +237,8 @@ struct dml2_configuration_options {
 	bool use_clock_dc_limits;
 	bool gpuvm_enable;
 	struct dml2_soc_bb *bb_from_dmub;
+	int max_frac_urgent_for_min_fclk_x1000;
+	int min_fclk_for_urgent_workaround_khz;
 };
 
 /*
diff --git a/drivers/gpu/drm/amd/display/dc/resource/dcn35/dcn35_resource.c b/drivers/gpu/drm/amd/display/dc/resource/dcn35/dcn35_resource.c
index 67ab8c1962ff..1ce0f9ecff9c 100644
--- a/drivers/gpu/drm/amd/display/dc/resource/dcn35/dcn35_resource.c
+++ b/drivers/gpu/drm/amd/display/dc/resource/dcn35/dcn35_resource.c
@@ -2152,8 +2152,9 @@ static bool dcn35_resource_construct(
 	dc->dml2_options.callbacks.can_support_mclk_switch_using_fw_based_vblank_stretch = &dcn30_can_support_mclk_switch_using_fw_based_vblank_stretch;
 
 	dc->dml2_options.max_segments_per_hubp = 24;
-
 	dc->dml2_options.det_segment_size = DCN3_2_DET_SEG_SIZE;/*todo*/
+	dc->dml2_options.max_frac_urgent_for_min_fclk_x1000 = 900;
+	dc->dml2_options.min_fclk_for_urgent_workaround_khz = 400 * 1000;
 
 	if (dc->config.sdpif_request_limit_words_per_umc == 0)
 		dc->config.sdpif_request_limit_words_per_umc = 16;/*todo*/