drm/amd/display: Add symclk workaround during disable link output

[Why & How]
This is originally a change (9c75891) in DCN32 because of the lack
of interface to set TX while keeping symclk on. Adding this workaround
to DCN314 will resolve the current issue.

Fixes: 9c75891 ("drm/amd/display: rework recent update PHY state commit")
Reviewed-by: Nicholas Kazlauskas <Nicholas.Kazlauskas@amd.com>
Acked-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: Leo Chen <sancchen@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/dcn314/dcn314_hwseq.c

@@ -423,3 +423,68 @@ void dcn314_hubp_pg_control(struct dce_hwseq *hws, unsigned int hubp_inst, bool
 
 	PERF_TRACE();
 }
+static void apply_symclk_on_tx_off_wa(struct dc_link *link)
+{
+	/* There are use cases where SYMCLK is referenced by OTG. For instance
+	 * for TMDS signal, OTG relies SYMCLK even if TX video output is off.
+	 * However current link interface will power off PHY when disabling link
+	 * output. This will turn off SYMCLK generated by PHY. The workaround is
+	 * to identify such case where SYMCLK is still in use by OTG when we
+	 * power off PHY. When this is detected, we will temporarily power PHY
+	 * back on and move PHY's SYMCLK state to SYMCLK_ON_TX_OFF by calling
+	 * program_pix_clk interface. When OTG is disabled, we will then power
+	 * off PHY by calling disable link output again.
+	 *
+	 * In future dcn generations, we plan to rework transmitter control
+	 * interface so that we could have an option to set SYMCLK ON TX OFF
+	 * state in one step without this workaround
+	 */
+
+	struct dc *dc = link->ctx->dc;
+	struct pipe_ctx *pipe_ctx = NULL;
+	uint8_t i;
+
+	if (link->phy_state.symclk_ref_cnts.otg > 0) {
+		for (i = 0; i < MAX_PIPES; i++) {
+			pipe_ctx = &dc->current_state->res_ctx.pipe_ctx[i];
+			if (pipe_ctx->stream && pipe_ctx->stream->link == link && pipe_ctx->top_pipe == NULL) {
+				pipe_ctx->clock_source->funcs->program_pix_clk(
+						pipe_ctx->clock_source,
+						&pipe_ctx->stream_res.pix_clk_params,
+						dc->link_srv->dp_get_encoding_format(
+								&pipe_ctx->link_config.dp_link_settings),
+						&pipe_ctx->pll_settings);
+				link->phy_state.symclk_state = SYMCLK_ON_TX_OFF;
+				break;
+			}
+		}
+	}
+}
+
+void dcn314_disable_link_output(struct dc_link *link,
+		const struct link_resource *link_res,
+		enum signal_type signal)
+{
+	struct dc *dc = link->ctx->dc;
+	const struct link_hwss *link_hwss = get_link_hwss(link, link_res);
+	struct dmcu *dmcu = dc->res_pool->dmcu;
+
+	if (signal == SIGNAL_TYPE_EDP &&
+			link->dc->hwss.edp_backlight_control)
+		link->dc->hwss.edp_backlight_control(link, false);
+	else if (dmcu != NULL && dmcu->funcs->lock_phy)
+		dmcu->funcs->lock_phy(dmcu);
+
+	link_hwss->disable_link_output(link, link_res, signal);
+	link->phy_state.symclk_state = SYMCLK_OFF_TX_OFF;
+	/*
+	 * Add the logic to extract BOTH power up and power down sequences
+	 * from enable/disable link output and only call edp panel control
+	 * in enable_link_dp and disable_link_dp once.
+	 */
+	if (dmcu != NULL && dmcu->funcs->lock_phy)
+		dmcu->funcs->unlock_phy(dmcu);
+	dc->link_srv->dp_trace_source_sequence(link, DPCD_SOURCE_SEQ_AFTER_DISABLE_LINK_PHY);
+
+	apply_symclk_on_tx_off_wa(link);
+}

drivers/gpu/drm/amd/display/dc/dcn314/dcn314_hwseq.h

@@ -45,4 +45,6 @@ void dcn314_hubp_pg_control(struct dce_hwseq *hws, unsigned int hubp_inst, bool
 
 void dcn314_dpp_root_clock_control(struct dce_hwseq *hws, unsigned int dpp_inst, bool clock_on);
 
+void dcn314_disable_link_output(struct dc_link *link, const struct link_resource *link_res, enum signal_type signal);
+
 #endif /* __DC_HWSS_DCN314_H__ */

drivers/gpu/drm/amd/display/dc/dcn314/dcn314_init.c

@@ -105,7 +105,7 @@ static const struct hw_sequencer_funcs dcn314_funcs = {
 	.enable_lvds_link_output = dce110_enable_lvds_link_output,
 	.enable_tmds_link_output = dce110_enable_tmds_link_output,
 	.enable_dp_link_output = dce110_enable_dp_link_output,
-	.disable_link_output = dce110_disable_link_output,
+	.disable_link_output = dcn314_disable_link_output,
 	.z10_restore = dcn31_z10_restore,
 	.z10_save_init = dcn31_z10_save_init,
 	.set_disp_pattern_generator = dcn30_set_disp_pattern_generator,