drm/i915/fbdev: Extract intel_fbdev_fb_prefer_stolen()

Consolidate the "should we allocate fbdev fb in stolen?"
check into a helper function. Makes it easier to change the
heuristics without having to change so many places.

v2: rebase related changes and consolidate all the prefer
    stolen conditions into a single function (Vinod)

v3: avoid including intel_display_core.h (Jani)

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Vinod Govindapillai <vinod.govindapillai@intel.com>
Reviewed-by: Uma Shankar <uma.shankar@intel.com>
Acked-by: Mika Kahola <mika.kahola@intel.com>
Link: https://patch.msgid.link/20260220170908.201422-4-vinod.govindapillai@intel.com

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

@@ -17,6 +17,22 @@ u32 intel_fbdev_fb_pitch_align(u32 stride)
 	return ALIGN(stride, 64);
 }
 
+bool intel_fbdev_fb_prefer_stolen(struct drm_device *drm, unsigned int size)
+{
+	struct drm_i915_private *i915 = to_i915(drm);
+
+	/* Skip stolen on MTL as Wa_22018444074 mitigation. */
+	if (IS_METEORLAKE(i915))
+		return false;
+
+	/*
+	 * If the FB is too big, just don't use it since fbdev is not very
+	 * important and we should probably use that space with FBC or other
+	 * features.
+	 */
+	return i915->dsm.usable_size >= size * 2;
+}
+
 struct drm_gem_object *intel_fbdev_fb_bo_create(struct drm_device *drm, int size)
 {
 	struct drm_i915_private *i915 = to_i915(drm);
@@ -28,14 +44,7 @@ struct drm_gem_object *intel_fbdev_fb_bo_create(struct drm_device *drm, int size
 						  I915_BO_ALLOC_CONTIGUOUS |
 						  I915_BO_ALLOC_USER);
 	} else {
-		/*
+		if (intel_fbdev_fb_prefer_stolen(drm, size))
-		 * If the FB is too big, just don't use it since fbdev is not very
-		 * important and we should probably use that space with FBC or other
-		 * features.
-		 *
-		 * Also skip stolen on MTL as Wa_22018444074 mitigation.
-		 */
-		if (!IS_METEORLAKE(i915) && size * 2 < i915->dsm.usable_size)
 			obj = i915_gem_object_create_stolen(i915, size);
 		if (IS_ERR(obj))
 			obj = i915_gem_object_create_shmem(i915, size);

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

@@ -19,5 +19,6 @@ struct drm_gem_object *intel_fbdev_fb_bo_create(struct drm_device *drm, int size
 void intel_fbdev_fb_bo_destroy(struct drm_gem_object *obj);
 int intel_fbdev_fb_fill_info(struct drm_device *drm, struct fb_info *info,
 			     struct drm_gem_object *obj, struct i915_vma *vma);
+bool intel_fbdev_fb_prefer_stolen(struct drm_device *drm, unsigned int size);
 
 #endif

drivers/gpu/drm/i915/i915_initial_plane.c

@@ -9,6 +9,7 @@
 #include "display/intel_crtc.h"
 #include "display/intel_display_types.h"
 #include "display/intel_fb.h"
+#include "display/intel_fbdev_fb.h"
 #include "gem/i915_gem_lmem.h"
 #include "gem/i915_gem_region.h"
 
@@ -116,7 +117,7 @@ initial_plane_vma(struct drm_i915_private *i915,
 	 */
 	if (IS_ENABLED(CONFIG_FRAMEBUFFER_CONSOLE) &&
 	    mem == i915->mm.stolen_region &&
-	    size * 2 > i915->dsm.usable_size) {
+	    !intel_fbdev_fb_prefer_stolen(&i915->drm, size)) {
 		drm_dbg_kms(&i915->drm, "Initial FB size exceeds half of stolen, discarding\n");
 		return NULL;
 	}