drm/i915/fbc: dirty rect support for FBC

Dirty rectangle feature allows FBC to recompress a subsection
of a frame. When this feature is enabled, display will read
the scan lines between dirty rectangle start line and dirty
rectangle end line in subsequent frames.

Use the merged damage clip stored in the plane state to
configure the FBC dirty rect areas.

v2: - Move dirty rect handling to fbc state (Ville)

v3: - Use intel_fbc_dirty_rect_update_noarm (Ville)
    - Split plane damage collection and dirty rect preparation
    - Handle case where dirty rect fall outside the visible region

v4: - A state variable to check if we need to update dirty rect
    registers in case intel_fbc_can_flip_nuke() (Ville)

v5: - No need to use a separate valid flag, updates to the
      conditions for prepare damage rect (Ville)
    - Usage of locks in fbc dirty rect related functions (Ville)

v6: - updates dirty rect handling (Ville)

v7: - Loop through all planes in atomic state is good enough (Ville)

Bspec: 68881, 71675, 73424
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Vinod Govindapillai <vinod.govindapillai@intel.com>
Signed-off-by: Mika Kahola <mika.kahola@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250228093802.27091-8-vinod.govindapillai@intel.com

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

@@ -818,6 +818,9 @@ void intel_plane_update_noarm(struct intel_dsb *dsb,
 
 	trace_intel_plane_update_noarm(plane_state, crtc);
 
+	if (plane->fbc)
+		intel_fbc_dirty_rect_update_noarm(dsb, plane);
+
 	if (plane->update_noarm)
 		plane->update_noarm(dsb, plane, crtc_state, plane_state);
 }

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

@@ -7272,6 +7272,8 @@ static void intel_atomic_commit_tail(struct intel_atomic_state *state)
 
 	intel_atomic_prepare_plane_clear_colors(state);
 
+	intel_fbc_prepare_dirty_rect(state);
+
 	for_each_new_intel_crtc_in_state(state, crtc, new_crtc_state, i)
 		intel_atomic_dsb_finish(state, crtc);
 

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

@@ -88,6 +88,7 @@ struct intel_fbc_state {
 	u16 override_cfb_stride;
 	u16 interval;
 	s8 fence_id;
+	struct drm_rect dirty_rect;
 };
 
 struct intel_fbc {
@@ -523,6 +524,9 @@ static void ilk_fbc_deactivate(struct intel_fbc *fbc)
 	struct intel_display *display = fbc->display;
 	u32 dpfc_ctl;
 
+	if (HAS_FBC_DIRTY_RECT(display))
+		intel_de_write(display, XE3_FBC_DIRTY_CTL(fbc->id), 0);
+
 	/* Disable compression */
 	dpfc_ctl = intel_de_read(display, ILK_DPFC_CONTROL(fbc->id));
 	if (dpfc_ctl & DPFC_CTL_EN) {
@@ -665,6 +669,10 @@ static void ivb_fbc_activate(struct intel_fbc *fbc)
 	if (DISPLAY_VER(display) >= 20)
 		intel_de_write(display, ILK_DPFC_CONTROL(fbc->id), dpfc_ctl);
 
+	if (HAS_FBC_DIRTY_RECT(display))
+		intel_de_write(display, XE3_FBC_DIRTY_CTL(fbc->id),
+			       FBC_DIRTY_RECT_EN);
+
 	intel_de_write(display, ILK_DPFC_CONTROL(fbc->id),
 		       DPFC_CTL_EN | dpfc_ctl);
 }
@@ -1196,6 +1204,82 @@ static bool tiling_is_valid(const struct intel_plane_state *plane_state)
 		return i8xx_fbc_tiling_valid(plane_state);
 }
 
+static void
+intel_fbc_dirty_rect_update(struct intel_dsb *dsb, struct intel_fbc *fbc)
+{
+	struct intel_display *display = fbc->display;
+	const struct drm_rect *fbc_dirty_rect = &fbc->state.dirty_rect;
+
+	lockdep_assert_held(&fbc->lock);
+
+	intel_de_write_dsb(display, dsb, XE3_FBC_DIRTY_RECT(fbc->id),
+			   FBC_DIRTY_RECT_START_LINE(fbc_dirty_rect->y1) |
+			   FBC_DIRTY_RECT_END_LINE(fbc_dirty_rect->y2 - 1));
+}
+
+void
+intel_fbc_dirty_rect_update_noarm(struct intel_dsb *dsb,
+				  struct intel_plane *plane)
+{
+	struct intel_display *display = to_intel_display(plane);
+	struct intel_fbc *fbc = plane->fbc;
+
+	if (!HAS_FBC_DIRTY_RECT(display))
+		return;
+
+	mutex_lock(&fbc->lock);
+
+	if (fbc->state.plane == plane)
+		intel_fbc_dirty_rect_update(dsb, fbc);
+
+	mutex_unlock(&fbc->lock);
+}
+
+static void
+__intel_fbc_prepare_dirty_rect(const struct intel_plane_state *plane_state)
+{
+	struct intel_plane *plane = to_intel_plane(plane_state->uapi.plane);
+	struct intel_fbc *fbc = plane->fbc;
+	struct drm_rect *fbc_dirty_rect = &fbc->state.dirty_rect;
+	int width = drm_rect_width(&plane_state->uapi.src) >> 16;
+	const struct drm_rect *damage = &plane_state->damage;
+	int y_offset = plane_state->view.color_plane[0].y;
+
+	lockdep_assert_held(&fbc->lock);
+
+	if (drm_rect_visible(damage))
+		*fbc_dirty_rect = *damage;
+	else
+		/* dirty rect must cover at least one line */
+		*fbc_dirty_rect = DRM_RECT_INIT(0, y_offset, width, 1);
+}
+
+void
+intel_fbc_prepare_dirty_rect(struct intel_atomic_state *state)
+{
+	struct intel_display *display = to_intel_display(state);
+	struct intel_plane_state *plane_state;
+	struct intel_plane *plane;
+	int i;
+
+	if (!HAS_FBC_DIRTY_RECT(display))
+		return;
+
+	for_each_new_intel_plane_in_state(state, plane, plane_state, i) {
+		struct intel_fbc *fbc = plane->fbc;
+
+		if (!fbc)
+			continue;
+
+		mutex_lock(&fbc->lock);
+
+		if (fbc->state.plane == plane)
+			__intel_fbc_prepare_dirty_rect(plane_state);
+
+		mutex_unlock(&fbc->lock);
+	}
+}
+
 static void intel_fbc_update_state(struct intel_atomic_state *state,
 				   struct intel_crtc *crtc,
 				   struct intel_plane *plane)

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

@@ -13,6 +13,7 @@ struct intel_atomic_state;
 struct intel_crtc;
 struct intel_crtc_state;
 struct intel_display;
+struct intel_dsb;
 struct intel_fbc;
 struct intel_plane;
 struct intel_plane_state;
@@ -47,5 +48,8 @@ void intel_fbc_handle_fifo_underrun_irq(struct intel_display *display);
 void intel_fbc_reset_underrun(struct intel_display *display);
 void intel_fbc_crtc_debugfs_add(struct intel_crtc *crtc);
 void intel_fbc_debugfs_register(struct intel_display *display);
+void intel_fbc_prepare_dirty_rect(struct intel_atomic_state *state);
+void intel_fbc_dirty_rect_update_noarm(struct intel_dsb *dsb,
+				       struct intel_plane *plane);
 
 #endif /* __INTEL_FBC_H__ */