drm/amd/display: On clock init, maintain DISPCLK freq

[Description]
- On init if a display is connected, we need to maintain the DISPCLK
  frequency
- Even though DPG_EN=1, the display still requires the correct
  timing or it could cause audio corruption (if DISPCLK freq
  is reduced)
- Read the current DISPCLK freq and request the same value to ensure
  the timing is valid and unchanged
- However, add option to do a full pipe power down (including link)
  which will also avoid audio related issues
	- Disabled for the time being on dcn32

Reviewed-by: Jun Lei <Jun.Lei@amd.com>
Acked-by: Qingqing Zhuo <qingqing.zhuo@amd.com>
Signed-off-by: Alvin Lee <Alvin.Lee2@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/clk_mgr/dcn32/dcn32_clk_mgr.c

@@ -399,6 +399,23 @@ static void dcn32_update_clocks_update_dentist(
 
 }
 
+static int dcn32_get_dispclk_from_dentist(struct clk_mgr *clk_mgr_base)
+{
+	struct clk_mgr_internal *clk_mgr = TO_CLK_MGR_INTERNAL(clk_mgr_base);
+	uint32_t dispclk_wdivider;
+	int disp_divider;
+
+	REG_GET(DENTIST_DISPCLK_CNTL, DENTIST_DISPCLK_WDIVIDER, &dispclk_wdivider);
+	disp_divider = dentist_get_divider_from_did(dispclk_wdivider);
+
+	/* Return DISPCLK freq in Khz */
+	if (disp_divider)
+		return (DENTIST_DIVIDER_RANGE_SCALE_FACTOR * clk_mgr->base.dentist_vco_freq_khz) / disp_divider;
+
+	return 0;
+}
+
+
 static void dcn32_update_clocks(struct clk_mgr *clk_mgr_base,
 			struct dc_state *context,
 			bool safe_to_lower)
@@ -852,6 +869,7 @@ static struct clk_mgr_funcs dcn32_funcs = {
 		.are_clock_states_equal = dcn32_are_clock_states_equal,
 		.enable_pme_wa = dcn32_enable_pme_wa,
 		.is_smu_present = dcn32_is_smu_present,
+		.get_dispclk_from_dentist = dcn32_get_dispclk_from_dentist,
 };
 
 void dcn32_clk_mgr_construct(

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

@@ -877,6 +877,7 @@ struct dc_debug_options {
 	bool support_eDP1_5;
 	uint32_t fpo_vactive_margin_us;
 	bool disable_fpo_vactive;
+	bool disable_boot_optimizations;
 };
 
 struct gpu_info_soc_bounding_box_v1_0;

drivers/gpu/drm/amd/display/dc/dcn32/dcn32_hwseq.c

@@ -721,10 +721,19 @@ static void dcn32_initialize_min_clocks(struct dc *dc)
 	clocks->socclk_khz = dc->clk_mgr->bw_params->clk_table.entries[0].socclk_mhz * 1000;
 	clocks->dramclk_khz = dc->clk_mgr->bw_params->clk_table.entries[0].memclk_mhz * 1000;
 	clocks->dppclk_khz = dc->clk_mgr->bw_params->clk_table.entries[0].dppclk_mhz * 1000;
-	clocks->dispclk_khz = dc->clk_mgr->bw_params->clk_table.entries[0].dispclk_mhz * 1000;
-	clocks->ref_dtbclk_khz = dc->clk_mgr->bw_params->clk_table.entries[0].dtbclk_mhz * 1000;
-	clocks->fclk_p_state_change_support = true;
-	clocks->p_state_change_support = true;
+	if (dc->debug.disable_boot_optimizations) {
+		clocks->dispclk_khz = dc->clk_mgr->bw_params->clk_table.entries[0].dispclk_mhz * 1000;
+	} else {
+		/* Even though DPG_EN = 1 for the connected display, it still requires the
+		 * correct timing so we cannot set DISPCLK to min freq or it could cause
+		 * audio corruption. Read current DISPCLK from DENTIST and request the same
+		 * freq to ensure that the timing is valid and unchanged.
+		 */
+		clocks->dispclk_khz = dc->clk_mgr->funcs->get_dispclk_from_dentist(dc->clk_mgr);
+		clocks->ref_dtbclk_khz = dc->clk_mgr->bw_params->clk_table.entries[0].dtbclk_mhz * 1000;
+		clocks->fclk_p_state_change_support = true;
+		clocks->p_state_change_support = true;
+	}
 
 	dc->clk_mgr->funcs->update_clocks(
 			dc->clk_mgr,
@@ -823,7 +832,14 @@ void dcn32_init_hw(struct dc *dc)
 	 * everything down.
 	 */
 	if (dcb->funcs->is_accelerated_mode(dcb) || !dc->config.seamless_boot_edp_requested) {
-		hws->funcs.init_pipes(dc, dc->current_state);
+		/* Disable boot optimizations means power down everything including PHY, DIG,
+		 * and OTG (i.e. the boot is not optimized because we do a full power down).
+		 */
+		if (dc->hwss.enable_accelerated_mode && dc->debug.disable_boot_optimizations)
+			dc->hwss.enable_accelerated_mode(dc, dc->current_state);
+		else
+			hws->funcs.init_pipes(dc, dc->current_state);
+
 		if (dc->res_pool->hubbub->funcs->allow_self_refresh_control)
 			dc->res_pool->hubbub->funcs->allow_self_refresh_control(dc->res_pool->hubbub,
 					!dc->res_pool->hubbub->ctx->dc->debug.disable_stutter);

drivers/gpu/drm/amd/display/dc/dcn32/dcn32_resource.c

@@ -728,6 +728,7 @@ static const struct dc_debug_options debug_defaults_drv = {
 	.disable_fpo_optimizations = false,
 	.fpo_vactive_margin_us = 2000, // 2000us
 	.disable_fpo_vactive = true,
+	.disable_boot_optimizations = false,
 };
 
 static const struct dc_debug_options debug_defaults_diags = {

drivers/gpu/drm/amd/display/dc/dcn321/dcn321_resource.c

@@ -726,6 +726,7 @@ static const struct dc_debug_options debug_defaults_drv = {
 	.disable_fpo_optimizations = false,
 	.fpo_vactive_margin_us = 2000, // 2000us
 	.disable_fpo_vactive = true,
+	.disable_boot_optimizations = false,
 };
 
 static const struct dc_debug_options debug_defaults_diags = {

drivers/gpu/drm/amd/display/dc/inc/hw/clk_mgr.h

@@ -293,6 +293,9 @@ struct clk_mgr_funcs {
 
 	/* Get SMU present */
 	bool (*is_smu_present)(struct clk_mgr *clk_mgr);
+
+	int (*get_dispclk_from_dentist)(struct clk_mgr *clk_mgr_base);
+
 };
 
 struct clk_mgr {