drm/amd/display: Add w/a to reset PHY before link training in verify_link_cap

[Why]
PHY will sometimes be in bad state on hotplugging display from USB-C
dongle.

[How]
Add additional calls to disable and then enable PHY before link training
starts during verify_link_cap.
Signed-off-by: George Shen <george.shen@amd.com>
Reviewed-by: Tony Cheng <Tony.Cheng@amd.com>
Acked-by: Harry Wentland <harry.wentland@amd.com>
Acked-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c

@@ -1892,6 +1892,16 @@ bool dp_verify_link_cap(
 	/* disable PHY done possible by BIOS, will be done by driver itself */
 	dp_disable_link_phy(link, link->connector_signal);
 
+	/* Temporary Renoir-specific workaround for SWDEV-215184;
+	 * PHY will sometimes be in bad state on hotplugging display from certain USB-C dongle,
+	 * so add extra cycle of enabling and disabling the PHY before first link training.
+	 */
+	if (link->link_enc->features.flags.bits.DP_IS_USB_C &&
+			link->dc->debug.usbc_combo_phy_reset_wa) {
+		dp_enable_link_phy(link, link->connector_signal, dp_cs_id, cur);
+		dp_disable_link_phy(link, link->connector_signal);
+	}
+
 	dp_cs_id = get_clock_source_id(link);
 
 	/* link training starts with the maximum common settings

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

@@ -421,6 +421,7 @@ struct dc_debug_options {
 	bool disable_dram_clock_change_vactive_support;
 	bool validate_dml_output;
 	bool enable_dmcub_surface_flip;
+	bool usbc_combo_phy_reset_wa;
 };
 
 struct dc_debug_data {

drivers/gpu/drm/amd/display/dc/dcn21/dcn21_resource.c

@@ -835,7 +835,8 @@ static const struct dc_debug_options debug_defaults_drv = {
 		.scl_reset_length10 = true,
 		.sanity_checks = true,
 		.disable_48mhz_pwrdwn = false,
-		.nv12_iflip_vm_wa = true
+		.nv12_iflip_vm_wa = true,
+		.usbc_combo_phy_reset_wa = true
 };
 
 static const struct dc_debug_options debug_defaults_diags = {