[PATCH] RFC: WIP: drm/i915/fbc: Resize CFB full in non-full modeset paths

[José Roberto de Souza]

A simple page flip can cause the CFB required sized to increase and
if it is bigger than the currently allocated CFB it needs to be
resize to activate FBC again.

Until now this case was not being handled but CI is starting to
get some of this errors.

So here it will free the old CFB and a try to allocate the required
CFB in the schedule activation work, it will happen after one vblank
so is guarantee that FBC was completed disabled and is not using CFB.

Signed-off-by: José Roberto de Souza <jose.souza at intel.com>
---
 drivers/gpu/drm/i915/i915_drv.h  |  1 +
 drivers/gpu/drm/i915/intel_fbc.c | 49 ++++++++++++++++++++++++++--------------
 2 files changed, 33 insertions(+), 17 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 5373b171bb96..5405b0b0f1c0 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -566,6 +566,7 @@ struct intel_fbc {
 	} work;
 
 	const char *no_fbc_reason;
+	bool try_resize_cfb;
 };
 
 /*
diff --git a/drivers/gpu/drm/i915/intel_fbc.c b/drivers/gpu/drm/i915/intel_fbc.c
index 707d49c12638..ced11dd5747a 100644
--- a/drivers/gpu/drm/i915/intel_fbc.c
+++ b/drivers/gpu/drm/i915/intel_fbc.c
@@ -41,6 +41,11 @@
 #include "intel_drv.h"
 #include "i915_drv.h"
 
+#define NO_FBC_REASON_NOT_ENOUGH_STOLEN_MEM "not enough stolen memory"
+
+static void __intel_fbc_cleanup_cfb(struct drm_i915_private *dev_priv);
+static int intel_fbc_alloc_cfb(struct intel_crtc *crtc);
+
 static inline bool fbc_supported(struct drm_i915_private *dev_priv)
 {
 	return HAS_FBC(dev_priv);
@@ -446,6 +451,14 @@ static void intel_fbc_work_fn(struct work_struct *__work)
 		goto retry;
 	}
 
+	if (fbc->try_resize_cfb) {
+		__intel_fbc_cleanup_cfb(dev_priv);
+		if (intel_fbc_alloc_cfb(crtc)) {
+			fbc->no_fbc_reason = NO_FBC_REASON_NOT_ENOUGH_STOLEN_MEM;
+			goto out;
+		}
+	}
+
 	intel_fbc_hw_activate(dev_priv);
 
 	work->scheduled = false;
@@ -843,22 +856,6 @@ static bool intel_fbc_can_activate(struct intel_crtc *crtc)
 		return false;
 	}
 
-	/* It is possible for the required CFB size change without a
-	 * crtc->disable + crtc->enable since it is possible to change the
-	 * stride without triggering a full modeset. Since we try to
-	 * over-allocate the CFB, there's a chance we may keep FBC enabled even
-	 * if this happens, but if we exceed the current CFB size we'll have to
-	 * disable FBC. Notice that it would be possible to disable FBC, wait
-	 * for a frame, free the stolen node, then try to reenable FBC in case
-	 * we didn't get any invalidate/deactivate calls, but this would require
-	 * a lot of tracking just for a specific case. If we conclude it's an
-	 * important case, we can implement it later. */
-	if (intel_fbc_calculate_cfb_size(dev_priv, &fbc->state_cache) >
-	    fbc->compressed_fb.size * fbc->threshold) {
-		fbc->no_fbc_reason = "CFB requirements changed";
-		return false;
-	}
-
 	/*
 	 * Work around a problem on GEN9+ HW, where enabling FBC on a plane
 	 * having a Y offset that isn't divisible by 4 causes FIFO underrun
@@ -870,6 +867,24 @@ static bool intel_fbc_can_activate(struct intel_crtc *crtc)
 		return false;
 	}
 
+	/* It is possible for the required CFB size change without a
+	 * crtc->disable + crtc->enable since it is possible to change the
+	 * stride without triggering a full modeset. Since we try to
+	 * over-allocate the CFB, there's a chance we may keep FBC enabled even
+	 * if this happens, but if we exceed the current CFB size we'll have to
+	 * resize CFB.
+	 */
+	if (!drm_mm_node_allocated(&fbc->compressed_fb)) {
+		fbc->try_resize_cfb = true;
+		DRM_DEBUG_KMS("Previous try to resize failed, trying again in the next schedule activation");
+	} else if (intel_fbc_calculate_cfb_size(dev_priv, &fbc->state_cache) >
+		   fbc->compressed_fb.size * fbc->threshold) {
+		fbc->try_resize_cfb = true;
+		DRM_DEBUG_KMS("CFB requirements changed, next schedule activation will try to resize it");
+	} else {
+		fbc->try_resize_cfb = false;
+	}
+
 	return true;
 }
 
@@ -1192,7 +1207,7 @@ void intel_fbc_enable(struct intel_crtc *crtc,
 
 	intel_fbc_update_state_cache(crtc, crtc_state, plane_state);
 	if (intel_fbc_alloc_cfb(crtc)) {
-		fbc->no_fbc_reason = "not enough stolen memory";
+		fbc->no_fbc_reason = NO_FBC_REASON_NOT_ENOUGH_STOLEN_MEM;
 		goto out;
 	}
 
-- 
2.16.3