drm/i915: Adjust seamless_m_n flag behaviour

Make the seamless_m_n flag more like the update_pipe fastset
flag, ie. the flag will only be set if we need to do the seamless
M/N update, and in all other cases the flag is cleared. Also
rename the flag to update_m_n to make it more clear it's similar
to update_pipe.

I believe special casing seamless_m_n like this makes sense
as it also affects eg. vblank evasion. We can potentially avoid
some vblank evasion tricks, simplify some checks, and hopefully
will help with the VRR vs. M/N mess.

Cc: Manasi Navare <navaremanasi@chromium.org>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230901130440.2085-6-ville.syrjala@linux.intel.comReviewed-by: Manasi Navare <navaremanasi@chromium.org>

drivers/gpu/drm/i915/display/intel_atomic.c

@@ -259,6 +259,7 @@ intel_crtc_duplicate_state(struct drm_crtc *crtc)
 		drm_property_blob_get(crtc_state->post_csc_lut);
 
 	crtc_state->update_pipe = false;
+	crtc_state->update_m_n = false;
 	crtc_state->disable_lp_wm = false;
 	crtc_state->disable_cxsr = false;
 	crtc_state->update_wm_pre = false;

drivers/gpu/drm/i915/display/intel_crtc.c

@@ -510,7 +510,7 @@ static void intel_crtc_vblank_evade_scanlines(struct intel_atomic_state *state,
 	 * M/N is double buffered on the transcoder's undelayed vblank,
 	 * so with seamless M/N we must evade both vblanks.
 	 */
-	if (new_crtc_state->seamless_m_n && intel_crtc_needs_fastset(new_crtc_state))
+	if (new_crtc_state->update_m_n)
 		*min -= adjusted_mode->crtc_vblank_start - adjusted_mode->crtc_vdisplay;
 }
 

drivers/gpu/drm/i915/display/intel_display.c

@@ -5170,7 +5170,7 @@ intel_pipe_config_compare(const struct intel_crtc_state *current_config,
 	PIPE_CONF_CHECK_X(lane_lat_optim_mask);
 
 	if (HAS_DOUBLE_BUFFERED_M_N(dev_priv)) {
-		if (!fastset || !pipe_config->seamless_m_n)
+		if (!fastset || !pipe_config->update_m_n)
 			PIPE_CONF_CHECK_M_N(dp_m_n);
 	} else {
 		PIPE_CONF_CHECK_M_N(dp_m_n);
@@ -5308,7 +5308,7 @@ intel_pipe_config_compare(const struct intel_crtc_state *current_config,
 	if (IS_G4X(dev_priv) || DISPLAY_VER(dev_priv) >= 5)
 		PIPE_CONF_CHECK_I(pipe_bpp);
 
-	if (!fastset || !pipe_config->seamless_m_n) {
+	if (!fastset || !pipe_config->update_m_n) {
 		PIPE_CONF_CHECK_I(hw.pipe_mode.crtc_clock);
 		PIPE_CONF_CHECK_I(hw.adjusted_mode.crtc_clock);
 	}
@@ -5434,6 +5434,7 @@ int intel_modeset_all_pipes(struct intel_atomic_state *state,
 
 		crtc_state->uapi.mode_changed = true;
 		crtc_state->update_pipe = false;
+		crtc_state->update_m_n = false;
 
 		ret = drm_atomic_add_affected_connectors(&state->base,
 							 &crtc->base);
@@ -5551,13 +5552,14 @@ static void intel_crtc_check_fastset(const struct intel_crtc_state *old_crtc_sta
 {
 	struct drm_i915_private *i915 = to_i915(old_crtc_state->uapi.crtc->dev);
 
-	if (!intel_pipe_config_compare(old_crtc_state, new_crtc_state, true)) {
+	if (!intel_pipe_config_compare(old_crtc_state, new_crtc_state, true))
 		drm_dbg_kms(&i915->drm, "fastset requirement not met, forcing full modeset\n");
+	else
+		new_crtc_state->uapi.mode_changed = false;
 
-		return;
-	}
+	if (intel_crtc_needs_modeset(new_crtc_state))
+		new_crtc_state->update_m_n = false;
 
-	new_crtc_state->uapi.mode_changed = false;
 	if (!intel_crtc_needs_modeset(new_crtc_state))
 		new_crtc_state->update_pipe = true;
 }
@@ -6272,6 +6274,7 @@ int intel_atomic_check(struct drm_device *dev,
 			if (intel_cpu_transcoders_need_modeset(state, BIT(master))) {
 				new_crtc_state->uapi.mode_changed = true;
 				new_crtc_state->update_pipe = false;
+				new_crtc_state->update_m_n = false;
 			}
 		}
 
@@ -6284,6 +6287,7 @@ int intel_atomic_check(struct drm_device *dev,
 			if (intel_cpu_transcoders_need_modeset(state, trans)) {
 				new_crtc_state->uapi.mode_changed = true;
 				new_crtc_state->update_pipe = false;
+				new_crtc_state->update_m_n = false;
 			}
 		}
 
@@ -6291,6 +6295,7 @@ int intel_atomic_check(struct drm_device *dev,
 			if (intel_pipes_need_modeset(state, new_crtc_state->bigjoiner_pipes)) {
 				new_crtc_state->uapi.mode_changed = true;
 				new_crtc_state->update_pipe = false;
+				new_crtc_state->update_m_n = false;
 			}
 		}
 	}
@@ -6469,7 +6474,7 @@ static void intel_pipe_fastset(const struct intel_crtc_state *old_crtc_state,
 	    IS_BROADWELL(dev_priv) || IS_HASWELL(dev_priv))
 		hsw_set_linetime_wm(new_crtc_state);
 
-	if (new_crtc_state->seamless_m_n)
+	if (new_crtc_state->update_m_n)
 		intel_cpu_transcoder_set_m1_n1(crtc, new_crtc_state->cpu_transcoder,
 					       &new_crtc_state->dp_m_n);
 }
@@ -6605,8 +6610,7 @@ static void intel_update_crtc(struct intel_atomic_state *state,
 	 *
 	 * FIXME Should be synchronized with the start of vblank somehow...
 	 */
-	if (vrr_enabling(old_crtc_state, new_crtc_state) ||
-	    (new_crtc_state->seamless_m_n && intel_crtc_needs_fastset(new_crtc_state)))
+	if (vrr_enabling(old_crtc_state, new_crtc_state) || new_crtc_state->update_m_n)
 		intel_crtc_update_active_timings(new_crtc_state,
 						 new_crtc_state->vrr.enable);
 

drivers/gpu/drm/i915/display/intel_display_types.h

@@ -1083,6 +1083,7 @@ struct intel_crtc_state {
 
 	unsigned fb_bits; /* framebuffers to flip */
 	bool update_pipe; /* can a fast modeset be performed? */
+	bool update_m_n; /* update M/N seamlessly during fastset? */
 	bool disable_cxsr;
 	bool update_wm_pre, update_wm_post; /* watermarks are updated */
 	bool fifo_changed; /* FIFO split is changed */
@@ -1195,7 +1196,6 @@ struct intel_crtc_state {
 	/* m2_n2 for eDP downclock */
 	struct intel_link_m_n dp_m2_n2;
 	bool has_drrs;
-	bool seamless_m_n;
 
 	/* PSR is supported but might not be enabled due the lack of enabled planes */
 	bool has_psr;

drivers/gpu/drm/i915/display/intel_dp.c

@@ -2536,7 +2536,7 @@ intel_dp_drrs_compute_config(struct intel_connector *connector,
 	int pixel_clock;
 
 	if (has_seamless_m_n(connector))
-		pipe_config->seamless_m_n = true;
+		pipe_config->update_m_n = true;
 
 	if (!can_enable_drrs(connector, pipe_config, downclock_mode)) {
 		if (intel_cpu_transcoder_has_m2_n2(i915, pipe_config->cpu_transcoder))