drm/amd/display: Manually adjust strobe for DCN303

commit a9a1ac4 upstream.

why:
DCN303's 4 channel SOC BB causes problems at strobe

how:
workaround to manually adjust strobe calculation using FCLK
restrict.

Reviewed-by: Jun Lei <Jun.Lei@amd.com>
Acked-by: Agustin Gutierrez <agustin.gutierrez@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Martin Leung <Martin.Leung@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/gpu/drm/amd/display/dc/dcn303/dcn303_resource.c

@@ -1344,6 +1344,20 @@ void dcn303_update_bw_bounding_box(struct dc *dc, struct clk_bw_params *bw_param
 			dcn3_03_soc.clock_limits[i].phyclk_d18_mhz = dcn3_03_soc.clock_limits[0].phyclk_d18_mhz;
 			dcn3_03_soc.clock_limits[i].dscclk_mhz = dcn3_03_soc.clock_limits[0].dscclk_mhz;
 		}
+
+		// WA: patch strobe modes to compensate for DCN303 BW issue
+		if (dcn3_03_soc.num_chans <= 4) {
+			for (i = 0; i < dcn3_03_soc.num_states; i++) {
+				if (dcn3_03_soc.clock_limits[i].dram_speed_mts > 1700)
+					break;
+
+				if (dcn3_03_soc.clock_limits[i].dram_speed_mts >= 1500) {
+					dcn3_03_soc.clock_limits[i].dcfclk_mhz = 100;
+					dcn3_03_soc.clock_limits[i].fabricclk_mhz = 100;
+				}
+			}
+		}
+
 		/* re-init DML with updated bb */
 		dml_init_instance(&dc->dml, &dcn3_03_soc, &dcn3_03_ip, DML_PROJECT_DCN30);
 		if (dc->current_state)