[PATCH 2/2] drm/i915/intel_panel: Use highest refresh rate mode for seamless VRR changes

[Ankit Nautiyal <ankit.k.nautiyal@intel.com>]

intel_panel_fixed_mode() intends to choose a fixed mode at or above the
requested refresh rate for VRR panels, so the requested refresh can be
reached by extending vblank.

This is called in compute config to find the 'best' fixed mode for a
requested mode and also called during mode valid phase to prune the
unsupported fixed modes.

For Non-VRR panels there is no issue:
- When a user wants to do a full modeset (sets DRM_MODE_ALLOW_MODESET
  flag) with a custom mode, the intel_panel_fixed_mode() gives the mode
  with refresh rate nearest to the requested mode.
- Seamless switch to a lower mode is only possible if the platform has
  support for Double buffered MN and the sink is Seamless-DRRS capable.
  In this case the user sets a lower refresh rate mode and doesn't set
  the DRM_MODE_ALLOW_MODESET flag the intel_panel_fixed_mode() returns
  again the fixed mode whose refresh rate is nearest to the requested
  mode.
- Since Duble buffered MN is not supported on LNL+, the seamless switch
  is not possible for such panels from LNL+.

For VRR panels the current logic has some issues:
- For VRR panels intel_panel_fixed_mode() intends to choose a fixed mode
  at or above the requested refresh rate so the requested refresh can be
  reached by extending vblank.
- However, as per the current logic the helper can return a lower refresh
  rate mode, if the lower refresh rate mode is first in the list of fixed
  mode. Later, if the selected fixed mode's refresh rate < the requested
  mode's refresh rate, then the requested rate is matched by extending
  the vblank. 
- In case of a full modeset request with a custom mode this is not a
  problem. But for the seamless switch features like LRR (Lower Refresh
  Rate) and the Seamless-DRRS this creates a problem as this results in
  change in vsync_start/end and resulting in a full modeset.
- Furthermore, as with the Non-VRR panel case, the Seamless-DRRS is not
  supported on LNL+, but for VRR panels, the vblank can be extended
  similar to LRR case. But due to the above mentioned problem in the
  intel_panel_fixed_mode() this also results in full modeset.

To solve these problems for the VRR panels, identify if the user wants a
full modeset or expects seamless switch. If seamless switch to a lower
mode is desired, make intel_panel_fixed_mode() return the highest
refresh rate mode, provided the requested rate is in vrr range. This
will then be modified to extend the vblank to provide the desired
refresh rate.

This is particularly needed for DRRS panels on platforms without the
double buffered M/N support (display version 20+), where seamless clock
changes are not possible.

To understand the user requirement for full modeset/seamless switch, the
intel_panel_fixed_mode() and intel_panel_compute_config() need access to
the connector state to check the allow_modeset flag.

Add a nullable conn_state parameter to both. The mode_valid callers pass
NULL since they have no atomic state and the compute_config callers pass
their conn_state.

Also remove the VRR check from is_best_fixed_mode() since the selection is
handled upfront in intel_panel_fixed_mode().

Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
---
 drivers/gpu/drm/i915/display/icl_dsi.c     |  2 +-
 drivers/gpu/drm/i915/display/intel_dp.c    |  6 ++--
 drivers/gpu/drm/i915/display/intel_dsi.c   |  2 +-
 drivers/gpu/drm/i915/display/intel_dvo.c   |  6 ++--
 drivers/gpu/drm/i915/display/intel_lvds.c  |  4 +--
 drivers/gpu/drm/i915/display/intel_panel.c | 35 +++++++++++-----------
 drivers/gpu/drm/i915/display/intel_panel.h |  6 ++--
 drivers/gpu/drm/i915/display/intel_sdvo.c  |  8 ++---
 drivers/gpu/drm/i915/display/vlv_dsi.c     |  2 +-
 9 files changed, 37 insertions(+), 34 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/icl_dsi.c b/drivers/gpu/drm/i915/display/icl_dsi.c
index afbaa0465842..1efe81404d01 100644
--- a/drivers/gpu/drm/i915/display/icl_dsi.c
+++ b/drivers/gpu/drm/i915/display/icl_dsi.c
@@ -1671,7 +1671,7 @@ static int gen11_dsi_compute_config(struct intel_encoder *encoder,
 	pipe_config->sink_format = INTEL_OUTPUT_FORMAT_RGB;
 	pipe_config->output_format = INTEL_OUTPUT_FORMAT_RGB;
 
-	ret = intel_panel_compute_config(intel_connector, adjusted_mode);
+	ret = intel_panel_compute_config(intel_connector, adjusted_mode, conn_state);
 	if (ret)
 		return ret;
 
diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
index 35b8fb5740aa..f014ce28e69f 100644
--- a/drivers/gpu/drm/i915/display/intel_dp.c
+++ b/drivers/gpu/drm/i915/display/intel_dp.c
@@ -1588,7 +1588,7 @@ intel_dp_mode_valid(struct drm_connector *_connector,
 	if (intel_dp_hdisplay_bad(display, mode->hdisplay))
 		return MODE_H_ILLEGAL;
 
-	fixed_mode = intel_panel_fixed_mode(connector, mode);
+	fixed_mode = intel_panel_fixed_mode(connector, mode, NULL);
 	if (intel_dp_is_edp(intel_dp) && fixed_mode) {
 		status = intel_panel_mode_valid(connector, mode);
 		if (status != MODE_OK)
@@ -3577,9 +3577,9 @@ intel_dp_compute_config(struct intel_encoder *encoder,
 	struct intel_connector *connector = intel_dp->attached_connector;
 	int ret = 0, link_bpp_x16;
 
-	fixed_mode = intel_panel_fixed_mode(connector, adjusted_mode);
+	fixed_mode = intel_panel_fixed_mode(connector, adjusted_mode, conn_state);
 	if (intel_dp_is_edp(intel_dp) && fixed_mode) {
-		ret = intel_panel_compute_config(connector, adjusted_mode);
+		ret = intel_panel_compute_config(connector, adjusted_mode, conn_state);
 		if (ret)
 			return ret;
 	}
diff --git a/drivers/gpu/drm/i915/display/intel_dsi.c b/drivers/gpu/drm/i915/display/intel_dsi.c
index 9005c1f5d857..a480bb79dca7 100644
--- a/drivers/gpu/drm/i915/display/intel_dsi.c
+++ b/drivers/gpu/drm/i915/display/intel_dsi.c
@@ -64,7 +64,7 @@ enum drm_mode_status intel_dsi_mode_valid(struct drm_connector *connector,
 	struct intel_display *display = to_intel_display(connector->dev);
 	struct intel_connector *intel_connector = to_intel_connector(connector);
 	const struct drm_display_mode *fixed_mode =
-		intel_panel_fixed_mode(intel_connector, mode);
+		intel_panel_fixed_mode(intel_connector, mode, NULL);
 	int max_dotclk = display->cdclk.max_dotclk_freq;
 	enum drm_mode_status status;
 
diff --git a/drivers/gpu/drm/i915/display/intel_dvo.c b/drivers/gpu/drm/i915/display/intel_dvo.c
index 405b33aca9dd..0ec25d895777 100644
--- a/drivers/gpu/drm/i915/display/intel_dvo.c
+++ b/drivers/gpu/drm/i915/display/intel_dvo.c
@@ -224,7 +224,7 @@ intel_dvo_mode_valid(struct drm_connector *_connector,
 	struct intel_connector *connector = to_intel_connector(_connector);
 	struct intel_dvo *intel_dvo = intel_attached_dvo(connector);
 	const struct drm_display_mode *fixed_mode =
-		intel_panel_fixed_mode(connector, mode);
+		intel_panel_fixed_mode(connector, mode, NULL);
 	int max_dotclk = display->cdclk.max_dotclk_freq;
 	int target_clock = mode->clock;
 	enum drm_mode_status status;
@@ -259,7 +259,7 @@ static int intel_dvo_compute_config(struct intel_encoder *encoder,
 	struct intel_connector *connector = to_intel_connector(conn_state->connector);
 	struct drm_display_mode *adjusted_mode = &pipe_config->hw.adjusted_mode;
 	const struct drm_display_mode *fixed_mode =
-		intel_panel_fixed_mode(intel_dvo->attached_connector, adjusted_mode);
+		intel_panel_fixed_mode(intel_dvo->attached_connector, adjusted_mode, conn_state);
 
 	/*
 	 * If we have timings from the BIOS for the panel, put them in
@@ -270,7 +270,7 @@ static int intel_dvo_compute_config(struct intel_encoder *encoder,
 	if (fixed_mode) {
 		int ret;
 
-		ret = intel_panel_compute_config(connector, adjusted_mode);
+		ret = intel_panel_compute_config(connector, adjusted_mode, conn_state);
 		if (ret)
 			return ret;
 	}
diff --git a/drivers/gpu/drm/i915/display/intel_lvds.c b/drivers/gpu/drm/i915/display/intel_lvds.c
index cc6d4bfcff10..2e30bc3f1e62 100644
--- a/drivers/gpu/drm/i915/display/intel_lvds.c
+++ b/drivers/gpu/drm/i915/display/intel_lvds.c
@@ -396,7 +396,7 @@ intel_lvds_mode_valid(struct drm_connector *_connector,
 	struct intel_display *display = to_intel_display(_connector->dev);
 	struct intel_connector *connector = to_intel_connector(_connector);
 	const struct drm_display_mode *fixed_mode =
-		intel_panel_fixed_mode(connector, mode);
+		intel_panel_fixed_mode(connector, mode, NULL);
 	int max_pixclk = display->cdclk.max_dotclk_freq;
 	enum drm_mode_status status;
 
@@ -460,7 +460,7 @@ static int intel_lvds_compute_config(struct intel_encoder *encoder,
 	 * with the panel scaling set up to source from the H/VDisplay
 	 * of the original mode.
 	 */
-	ret = intel_panel_compute_config(connector, adjusted_mode);
+	ret = intel_panel_compute_config(connector, adjusted_mode, conn_state);
 	if (ret)
 		return ret;
 
diff --git a/drivers/gpu/drm/i915/display/intel_panel.c b/drivers/gpu/drm/i915/display/intel_panel.c
index 5e918ee0c8ea..65d017371d78 100644
--- a/drivers/gpu/drm/i915/display/intel_panel.c
+++ b/drivers/gpu/drm/i915/display/intel_panel.c
@@ -59,24 +59,13 @@ intel_panel_preferred_fixed_mode(struct intel_connector *connector)
 					struct drm_display_mode, head);
 }
 
-static bool is_best_fixed_mode(struct intel_connector *connector,
-			       int vrefresh, int fixed_mode_vrefresh,
+static bool is_best_fixed_mode(int vrefresh, int fixed_mode_vrefresh,
 			       const struct drm_display_mode *best_mode)
 {
 	/* we want to always return something */
 	if (!best_mode)
 		return true;
 
-	/*
-	 * With VRR always pick a mode with equal/higher than requested
-	 * vrefresh, which we can then reduce to match the requested
-	 * vrefresh by extending the vblank length.
-	 */
-	if (intel_vrr_is_in_range(connector, vrefresh) &&
-	    intel_vrr_is_in_range(connector, fixed_mode_vrefresh) &&
-	    fixed_mode_vrefresh < vrefresh)
-		return false;
-
 	/* pick the fixed_mode that is closest in terms of vrefresh */
 	return abs(fixed_mode_vrefresh - vrefresh) <
 		abs(drm_mode_vrefresh(best_mode) - vrefresh);
@@ -84,15 +73,26 @@ static bool is_best_fixed_mode(struct intel_connector *connector,
 
 const struct drm_display_mode *
 intel_panel_fixed_mode(struct intel_connector *connector,
-		       const struct drm_display_mode *mode)
+		       const struct drm_display_mode *mode,
+		       const struct drm_connector_state *conn_state)
 {
 	const struct drm_display_mode *fixed_mode, *best_mode = NULL;
 	int vrefresh = drm_mode_vrefresh(mode);
 
+	/*
+	 * With VRR always pick the highest refresh rate mode,
+	 * which we can then reduce to match the requested
+	 * vrefresh by extending the vblank length.
+	 */
+	if (conn_state && !conn_state->state->allow_modeset &&
+	    intel_vrr_is_capable(connector) &&
+	    intel_vrr_is_in_range(connector, vrefresh))
+		return intel_panel_highest_vrefresh_mode(connector);
+
 	list_for_each_entry(fixed_mode, &connector->panel.fixed_modes, head) {
 		int fixed_mode_vrefresh = drm_mode_vrefresh(fixed_mode);
 
-		if (is_best_fixed_mode(connector, vrefresh,
+		if (is_best_fixed_mode(vrefresh,
 				       fixed_mode_vrefresh, best_mode))
 			best_mode = fixed_mode;
 	}
@@ -213,10 +213,11 @@ enum drrs_type intel_panel_drrs_type(struct intel_connector *connector)
 }
 
 int intel_panel_compute_config(struct intel_connector *connector,
-			       struct drm_display_mode *adjusted_mode)
+			       struct drm_display_mode *adjusted_mode,
+			       const struct drm_connector_state *conn_state)
 {
 	const struct drm_display_mode *fixed_mode =
-		intel_panel_fixed_mode(connector, adjusted_mode);
+		intel_panel_fixed_mode(connector, adjusted_mode, conn_state);
 	int vrefresh, fixed_mode_vrefresh;
 	bool is_vrr;
 
@@ -414,7 +415,7 @@ intel_panel_mode_valid(struct intel_connector *connector,
 		       const struct drm_display_mode *mode)
 {
 	const struct drm_display_mode *fixed_mode =
-		intel_panel_fixed_mode(connector, mode);
+		intel_panel_fixed_mode(connector, mode, NULL);
 
 	if (!fixed_mode)
 		return MODE_OK;
diff --git a/drivers/gpu/drm/i915/display/intel_panel.h b/drivers/gpu/drm/i915/display/intel_panel.h
index 2f7a317995ea..c1189a20c8b2 100644
--- a/drivers/gpu/drm/i915/display/intel_panel.h
+++ b/drivers/gpu/drm/i915/display/intel_panel.h
@@ -32,7 +32,8 @@ const struct drm_display_mode *
 intel_panel_preferred_fixed_mode(struct intel_connector *connector);
 const struct drm_display_mode *
 intel_panel_fixed_mode(struct intel_connector *connector,
-		       const struct drm_display_mode *mode);
+		       const struct drm_display_mode *mode,
+		       const struct drm_connector_state *conn_state);
 const struct drm_display_mode *
 intel_panel_downclock_mode(struct intel_connector *connector,
 			   const struct drm_display_mode *adjusted_mode);
@@ -47,7 +48,8 @@ enum drm_mode_status
 intel_panel_mode_valid(struct intel_connector *connector,
 		       const struct drm_display_mode *mode);
 int intel_panel_compute_config(struct intel_connector *connector,
-			       struct drm_display_mode *adjusted_mode);
+			       struct drm_display_mode *adjusted_mode,
+			       const struct drm_connector_state *conn_state);
 void intel_panel_add_edid_fixed_modes(struct intel_connector *connector,
 				      bool use_alt_fixed_modes);
 void intel_panel_add_vbt_lfp_fixed_mode(struct intel_connector *connector);
diff --git a/drivers/gpu/drm/i915/display/intel_sdvo.c b/drivers/gpu/drm/i915/display/intel_sdvo.c
index 2e1af9e869de..e07c1070a3ec 100644
--- a/drivers/gpu/drm/i915/display/intel_sdvo.c
+++ b/drivers/gpu/drm/i915/display/intel_sdvo.c
@@ -797,7 +797,7 @@ intel_sdvo_create_preferred_input_timing(struct intel_sdvo *intel_sdvo,
 
 	if (IS_LVDS(intel_sdvo_connector)) {
 		const struct drm_display_mode *fixed_mode =
-			intel_panel_fixed_mode(&intel_sdvo_connector->base, mode);
+			intel_panel_fixed_mode(&intel_sdvo_connector->base, mode, NULL);
 
 		if (fixed_mode->hdisplay != args.width ||
 		    fixed_mode->vdisplay != args.height)
@@ -1396,11 +1396,11 @@ static int intel_sdvo_compute_config(struct intel_encoder *encoder,
 		pipe_config->sdvo_tv_clock = true;
 	} else if (IS_LVDS(intel_sdvo_connector)) {
 		const struct drm_display_mode *fixed_mode =
-			intel_panel_fixed_mode(&intel_sdvo_connector->base, mode);
+			intel_panel_fixed_mode(&intel_sdvo_connector->base, mode, conn_state);
 		int ret;
 
 		ret = intel_panel_compute_config(&intel_sdvo_connector->base,
-						 adjusted_mode);
+						 adjusted_mode, conn_state);
 		if (ret)
 			return ret;
 
@@ -1562,7 +1562,7 @@ static void intel_sdvo_pre_enable(struct intel_atomic_state *state,
 	/* lvds has a special fixed output timing. */
 	if (IS_LVDS(intel_sdvo_connector)) {
 		const struct drm_display_mode *fixed_mode =
-			intel_panel_fixed_mode(&intel_sdvo_connector->base, mode);
+			intel_panel_fixed_mode(&intel_sdvo_connector->base, mode, conn_state);
 
 		intel_sdvo_get_dtd_from_mode(&output_dtd, fixed_mode);
 	} else {
diff --git a/drivers/gpu/drm/i915/display/vlv_dsi.c b/drivers/gpu/drm/i915/display/vlv_dsi.c
index 76e8cd0f65a4..bfe465443d20 100644
--- a/drivers/gpu/drm/i915/display/vlv_dsi.c
+++ b/drivers/gpu/drm/i915/display/vlv_dsi.c
@@ -280,7 +280,7 @@ static int intel_dsi_compute_config(struct intel_encoder *encoder,
 	pipe_config->sink_format = INTEL_OUTPUT_FORMAT_RGB;
 	pipe_config->output_format = INTEL_OUTPUT_FORMAT_RGB;
 
-	ret = intel_panel_compute_config(intel_connector, adjusted_mode);
+	ret = intel_panel_compute_config(intel_connector, adjusted_mode, conn_state);
 	if (ret)
 		return ret;
 
-- 
2.45.2