[Intel-gfx] [PATCH] drm/i915/gem: Don't try to map and fence 8K/bigjoiner scanout buffers

[Vivek Kasireddy <vivek.kasireddy@intel.com>]

On platforms capable of allowing 8K (7680 x 4320) modes, pinning 2 or
more framebuffers/scanout buffers results in only one that is mappable/
fenceable. Therefore, pageflipping between these 2 FBs where only one
is mappable/fenceable creates latencies large enough to miss alternate
vblanks thereby producing less optimal framerate.

This mainly happens because when i915_gem_object_pin_to_display_plane()
is called to pin one of the FB objs, the associated vma is identified
as misplaced and therefore i915_vma_unbind() is called which unbinds and
evicts it. This misplaced vma gets subseqently pinned only when
i915_gem_object_ggtt_pin_ww() is called without the mappable flag. This
results in a latency of ~10ms and happens every other vblank/repaint cycle.

Testcase:
Running Weston and weston-simple-egl on an Alderlake_S (ADLS) platform
with a 8K@60 mode results in only ~40 FPS. Since upstream Weston submits
a frame ~7ms before the next vblank, the latencies seen between atomic
commit and flip event is 7, 24 (7 + 16.66), 7, 24..... suggesting that
it misses the vblank every other frame.

Here is the ftrace snippet that shows the source of the ~10ms latency:
              i915_gem_object_pin_to_display_plane() {
0.102 us   |    i915_gem_object_set_cache_level();
                i915_gem_object_ggtt_pin_ww() {
0.390 us   |      i915_vma_instance();
0.178 us   |      i915_vma_misplaced();
                  i915_vma_unbind() {
                  __i915_active_wait() {
0.082 us   |        i915_active_acquire_if_busy();
0.475 us   |      }
                  intel_runtime_pm_get() {
0.087 us   |        intel_runtime_pm_acquire();
0.259 us   |      }
                  __i915_active_wait() {
0.085 us   |        i915_active_acquire_if_busy();
0.240 us   |      }
                  __i915_vma_evict() {
                    ggtt_unbind_vma() {
                      gen8_ggtt_clear_range() {
10507.255 us |        }
10507.689 us |      }
10508.516 us |   }

Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Cc: Manasi Navare <manasi.d.navare@intel.com>
Signed-off-by: Vivek Kasireddy <vivek.kasireddy@intel.com>
---
 drivers/gpu/drm/i915/display/intel_fb_pin.c  | 11 +++++++++--
 drivers/gpu/drm/i915/display/intel_overlay.c | 11 ++++++++---
 drivers/gpu/drm/i915/gem/i915_gem_domain.c   |  6 ++++--
 drivers/gpu/drm/i915/gem/i915_gem_object.h   |  3 ++-
 4 files changed, 23 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_fb_pin.c b/drivers/gpu/drm/i915/display/intel_fb_pin.c
index 3f77f3013584..53c156d9a9f9 100644
--- a/drivers/gpu/drm/i915/display/intel_fb_pin.c
+++ b/drivers/gpu/drm/i915/display/intel_fb_pin.c
@@ -144,7 +144,7 @@ intel_pin_and_fence_fb_obj(struct drm_framebuffer *fb,
 
 	if (!ret) {
 		vma = i915_gem_object_pin_to_display_plane(obj, &ww, alignment,
-							   view, pinctl);
+							   view, pinctl, uses_fence);
 		if (IS_ERR(vma)) {
 			ret = PTR_ERR(vma);
 			goto err_unpin;
@@ -218,9 +218,16 @@ int intel_plane_pin_fb(struct intel_plane_state *plane_state)
 		INTEL_INFO(dev_priv)->display.cursor_needs_physical;
 
 	if (!intel_fb_uses_dpt(fb)) {
+		struct intel_crtc *crtc = to_intel_crtc(plane_state->hw.crtc);
+		struct intel_crtc_state *crtc_state =
+					to_intel_crtc_state(crtc->base.state);
+		bool uses_fence = intel_plane_uses_fence(plane_state);
+		bool is_bigjoiner = crtc_state->bigjoiner ||
+				    crtc_state->bigjoiner_slave;
+
 		vma = intel_pin_and_fence_fb_obj(fb, phys_cursor,
 						 &plane_state->view.gtt,
-						 intel_plane_uses_fence(plane_state),
+						 uses_fence && !is_bigjoiner,
 						 &plane_state->flags);
 		if (IS_ERR(vma))
 			return PTR_ERR(vma);
diff --git a/drivers/gpu/drm/i915/display/intel_overlay.c b/drivers/gpu/drm/i915/display/intel_overlay.c
index 7e3f5c6ca484..e9563b40b911 100644
--- a/drivers/gpu/drm/i915/display/intel_overlay.c
+++ b/drivers/gpu/drm/i915/display/intel_overlay.c
@@ -755,10 +755,14 @@ static u32 overlay_cmd_reg(struct drm_intel_overlay_put_image *params)
 	return cmd;
 }
 
-static struct i915_vma *intel_overlay_pin_fb(struct drm_i915_gem_object *new_bo)
+static struct i915_vma *intel_overlay_pin_fb(struct drm_i915_gem_object *new_bo,
+					     struct intel_overlay *overlay)
 {
 	struct i915_gem_ww_ctx ww;
 	struct i915_vma *vma;
+	const struct intel_plane_state *plane_state =
+		to_intel_plane_state(overlay->crtc->base.primary->state);
+	bool uses_fence = intel_plane_uses_fence(plane_state);
 	int ret;
 
 	i915_gem_ww_ctx_init(&ww, true);
@@ -766,7 +770,8 @@ static struct i915_vma *intel_overlay_pin_fb(struct drm_i915_gem_object *new_bo)
 	ret = i915_gem_object_lock(new_bo, &ww);
 	if (!ret) {
 		vma = i915_gem_object_pin_to_display_plane(new_bo, &ww, 0,
-							   NULL, PIN_MAPPABLE);
+							   NULL, PIN_MAPPABLE,
+							   uses_fence);
 		ret = PTR_ERR_OR_ZERO(vma);
 	}
 	if (ret == -EDEADLK) {
@@ -802,7 +807,7 @@ static int intel_overlay_do_put_image(struct intel_overlay *overlay,
 
 	atomic_inc(&dev_priv->gpu_error.pending_fb_pin);
 
-	vma = intel_overlay_pin_fb(new_bo);
+	vma = intel_overlay_pin_fb(new_bo, overlay);
 	if (IS_ERR(vma)) {
 		ret = PTR_ERR(vma);
 		goto out_pin_section;
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_domain.c b/drivers/gpu/drm/i915/gem/i915_gem_domain.c
index b684a62bf3b0..b9108f13cc49 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_domain.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_domain.c
@@ -375,7 +375,8 @@ i915_gem_object_pin_to_display_plane(struct drm_i915_gem_object *obj,
 				     struct i915_gem_ww_ctx *ww,
 				     u32 alignment,
 				     const struct i915_ggtt_view *view,
-				     unsigned int flags)
+				     unsigned int flags,
+				     bool uses_fence)
 {
 	struct drm_i915_private *i915 = to_i915(obj->base.dev);
 	struct i915_vma *vma;
@@ -411,7 +412,8 @@ i915_gem_object_pin_to_display_plane(struct drm_i915_gem_object *obj,
 	 */
 	vma = ERR_PTR(-ENOSPC);
 	if ((flags & PIN_MAPPABLE) == 0 &&
-	    (!view || view->type == I915_GGTT_VIEW_NORMAL))
+	    (!view || view->type == I915_GGTT_VIEW_NORMAL) &&
+	    uses_fence)
 		vma = i915_gem_object_ggtt_pin_ww(obj, ww, view, 0, alignment,
 						  flags | PIN_MAPPABLE |
 						  PIN_NONBLOCK);
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_object.h b/drivers/gpu/drm/i915/gem/i915_gem_object.h
index a5479ac7a4ad..e83564fa57ca 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_object.h
+++ b/drivers/gpu/drm/i915/gem/i915_gem_object.h
@@ -534,7 +534,8 @@ i915_gem_object_pin_to_display_plane(struct drm_i915_gem_object *obj,
 				     struct i915_gem_ww_ctx *ww,
 				     u32 alignment,
 				     const struct i915_ggtt_view *view,
-				     unsigned int flags);
+				     unsigned int flags,
+				     bool uses_fence);
 
 void i915_gem_object_make_unshrinkable(struct drm_i915_gem_object *obj);
 void i915_gem_object_make_shrinkable(struct drm_i915_gem_object *obj);
-- 
2.31.1