drm/amd/display: Add support for toggling DFS bypass

[Why]

If the hardware supports DFS bypass it will always be enabled after
creation of the DCCG. DFS bypass should only be enabled when
the current stream consists of a single embedded panel and the
minimum display clock is below the DFS bypass threshold.

[How]

Add a function to the DCCG table that updates the DFS bypass state
when setting the bandwidth. If the DFS bypass state is changed, the
clock needs to be reprogrammed to reflect this before the DPREFCLK
is updated for audio endpoints. The existing display clock value
is used as the target display clock value when reprogramming since the
resulting change will be equal or larger to the current value.

These changes only specifically target dce110 but do offer a framework
for support on other applicable targets.

Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Reviewed-by: David Francis <David.Francis@amd.com>
Acked-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/dce/dce_clocks.c

@@ -255,13 +255,12 @@ static int dce_set_clock(
 	pxl_clk_params.target_pixel_clock = requested_clk_khz;
 	pxl_clk_params.pll_id = CLOCK_SOURCE_ID_DFS;
 
-	if (clk_dce->dfs_bypass_enabled)
+	if (clk_dce->dfs_bypass_active)
 		pxl_clk_params.flags.SET_DISPCLK_DFS_BYPASS = true;
 
 	bp->funcs->program_display_engine_pll(bp, &pxl_clk_params);
 
-	if (clk_dce->dfs_bypass_enabled) {
-
+	if (clk_dce->dfs_bypass_active) {
 		/* Cache the fixed display clock*/
 		clk_dce->dfs_bypass_disp_clk =
 			pxl_clk_params.dfs_bypass_display_clock;
@@ -677,6 +676,61 @@ static void dce_update_clocks(struct dccg *dccg,
 	}
 }
 
+static bool dce_update_dfs_bypass(
+       struct dccg *dccg,
+       struct dc *dc,
+       struct dc_state *context,
+       int requested_clock_khz)
+{
+       struct dce_dccg *clk_dce = TO_DCE_CLOCKS(dccg);
+       struct resource_context *res_ctx = &context->res_ctx;
+       enum signal_type signal_type = SIGNAL_TYPE_NONE;
+       bool was_active = clk_dce->dfs_bypass_active;
+       int i;
+
+       /* Disable DFS bypass by default. */
+       clk_dce->dfs_bypass_active = false;
+
+       /* Check that DFS bypass is available. */
+       if (!clk_dce->dfs_bypass_enabled)
+               goto update;
+
+       /* Check if the requested display clock is below the threshold. */
+       if (requested_clock_khz >= 400000)
+               goto update;
+
+       /* DFS-bypass should only be enabled on single stream setups */
+       if (context->stream_count != 1)
+               goto update;
+
+       /* Check that the stream's signal type is an embedded panel */
+       for (i = 0; i < dc->res_pool->pipe_count; i++) {
+               if (res_ctx->pipe_ctx[i].stream) {
+                       struct pipe_ctx *pipe_ctx = &res_ctx->pipe_ctx[i];
+
+                       signal_type = pipe_ctx->stream->sink->link->connector_signal;
+                       break;
+               }
+       }
+
+       if (signal_type == SIGNAL_TYPE_EDP ||
+               signal_type == SIGNAL_TYPE_LVDS)
+               clk_dce->dfs_bypass_active = true;
+
+update:
+       /* Update the clock state. We don't need to respect safe_to_lower
+        * because DFS bypass should always be greater than the current
+        * display clock frequency.
+        */
+       if (was_active != clk_dce->dfs_bypass_active) {
+               dccg->clks.dispclk_khz =
+                       dccg->funcs->set_dispclk(dccg, dccg->clks.dispclk_khz);
+               return true;
+       }
+
+       return false;
+}
+
 #ifdef CONFIG_DRM_AMD_DC_DCN1_0
 static const struct display_clock_funcs dcn1_funcs = {
 	.get_dp_ref_clk_frequency = dce12_get_dp_ref_freq_khz,
@@ -700,7 +754,8 @@ static const struct display_clock_funcs dce112_funcs = {
 static const struct display_clock_funcs dce110_funcs = {
 	.get_dp_ref_clk_frequency = dce_get_dp_ref_freq_khz,
 	.set_dispclk = dce_psr_set_clock,
-	.update_clocks = dce_update_clocks
+	.update_clocks = dce_update_clocks,
+	.update_dfs_bypass = dce_update_dfs_bypass
 };
 
 static const struct display_clock_funcs dce_funcs = {

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

@@ -78,6 +78,8 @@ struct dce_dccg {
 
 	/* Cache the status of DFS-bypass feature*/
 	bool dfs_bypass_enabled;
+	/* True if the DFS-bypass feature is enabled and active. */
+	bool dfs_bypass_active;
 	/* Cache the display clock returned by VBIOS if DFS-bypass is enabled.
 	 * This is basically "Crystal Frequency In KHz" (XTALIN) frequency */
 	int dfs_bypass_disp_clk;

drivers/gpu/drm/amd/display/dc/dce110/dce110_hw_sequencer.c

@@ -2566,6 +2566,7 @@ void dce110_set_bandwidth(
 		bool decrease_allowed)
 {
 	struct dc_clocks req_clks;
+	struct dccg *dccg = dc->res_pool->dccg;
 
 	req_clks.dispclk_khz = context->bw.dce.dispclk_khz;
 	req_clks.phyclk_khz = get_max_pixel_clock_for_all_paths(dc, context);
@@ -2575,8 +2576,15 @@ void dce110_set_bandwidth(
 	else
 		dce110_set_safe_displaymarks(&context->res_ctx, dc->res_pool);
 
-	dc->res_pool->dccg->funcs->update_clocks(
-			dc->res_pool->dccg,
+	if (dccg->funcs->update_dfs_bypass)
+		dccg->funcs->update_dfs_bypass(
+			dccg,
+			dc,
+			context,
+			req_clks.dispclk_khz);
+
+	dccg->funcs->update_clocks(
+			dccg,
 			&req_clks,
 			decrease_allowed);
 	pplib_apply_display_requirements(dc, context);

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

@@ -53,6 +53,11 @@ struct display_clock_funcs {
 		int requested_clock_khz);
 
 	int (*get_dp_ref_clk_frequency)(struct dccg *dccg);
+
+	bool (*update_dfs_bypass)(struct dccg *dccg,
+		struct dc *dc,
+		struct dc_state *context,
+		int requested_clock_khz);
 };
 
 #endif /* __DISPLAY_CLOCK_H__ */