drm/i915: Allow more varied alternate fixed modes for panels

On some systems the panel reports alternate modes with
different blanking periods. If the EDID reports them and VBT
doesn't tell us otherwise then I can't really see why they
should be rejected. So allow their use for the purposes of
static DRRS.

For seamless DRRS we still require a much more exact match
of course. But that logic only kicks in when selecting the
downclock mode (or in the future when determining whether
we can do a seamless refresh rate change due to a user
modeset).

Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/6374Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220830212436.2021-1-ville.syrjala@linux.intel.comReviewed-by: Jani Nikula <jani.nikula@intel.com>

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

@@ -82,15 +82,14 @@ static bool is_alt_drrs_mode(const struct drm_display_mode *mode,
 		mode->clock != preferred_mode->clock;
 }
 
-static bool is_alt_vrr_mode(const struct drm_display_mode *mode,
-			    const struct drm_display_mode *preferred_mode)
+static bool is_alt_fixed_mode(const struct drm_display_mode *mode,
+			      const struct drm_display_mode *preferred_mode)
 {
 	return drm_mode_match(mode, preferred_mode,
 			      DRM_MODE_MATCH_FLAGS |
 			      DRM_MODE_MATCH_3D_FLAGS) &&
 		mode->hdisplay == preferred_mode->hdisplay &&
-		mode->vdisplay == preferred_mode->vdisplay &&
-		mode->clock != preferred_mode->clock;
+		mode->vdisplay == preferred_mode->vdisplay;
 }
 
 const struct drm_display_mode *
@@ -173,19 +172,7 @@ int intel_panel_compute_config(struct intel_connector *connector,
 	return 0;
 }
 
-static bool is_alt_fixed_mode(const struct drm_display_mode *mode,
-			      const struct drm_display_mode *preferred_mode,
-			      bool has_vrr)
-{
-	/* is_alt_drrs_mode() is a subset of is_alt_vrr_mode() */
-	if (has_vrr)
-		return is_alt_vrr_mode(mode, preferred_mode);
-	else
-		return is_alt_drrs_mode(mode, preferred_mode);
-}
-
-static void intel_panel_add_edid_alt_fixed_modes(struct intel_connector *connector,
-						 bool has_vrr)
+static void intel_panel_add_edid_alt_fixed_modes(struct intel_connector *connector)
 {
 	struct drm_i915_private *dev_priv = to_i915(connector->base.dev);
 	const struct drm_display_mode *preferred_mode =
@@ -193,7 +180,7 @@ static void intel_panel_add_edid_alt_fixed_modes(struct intel_connector *connect
 	struct drm_display_mode *mode, *next;
 
 	list_for_each_entry_safe(mode, next, &connector->base.probed_modes, head) {
-		if (!is_alt_fixed_mode(mode, preferred_mode, has_vrr))
+		if (!is_alt_fixed_mode(mode, preferred_mode))
 			continue;
 
 		drm_dbg_kms(&dev_priv->drm,
@@ -256,7 +243,7 @@ void intel_panel_add_edid_fixed_modes(struct intel_connector *connector,
 {
 	intel_panel_add_edid_preferred_mode(connector);
 	if (intel_panel_preferred_fixed_mode(connector) && (has_drrs || has_vrr))
-		intel_panel_add_edid_alt_fixed_modes(connector, has_vrr);
+		intel_panel_add_edid_alt_fixed_modes(connector);
 	intel_panel_destroy_probed_modes(connector);
 }