From 2ae9e3653f09121c224a1fbff617921d08b839ae Mon Sep 17 00:00:00 2001
From: Daniel Vetter <daniel.vetter@ffwll.ch>
Date: Fri, 11 Aug 2017 09:23:27 +0200
Subject: [PATCH] drm/i915/fbc: only update no_fbc_reason when active
Git-commit: 2ae9e3653f09121c224a1fbff617921d08b839ae
Patch-mainline: v4.14-rc1
References: FATE#322643 bsc#1055900

In our snb farm in CI we have plenty of underruns, but not enough
stolen memory to enable fbc. Which means every time there's an
underrun the no_fbc_reason swichtes to something that makes
kms_frontbuffer_tracking fail instead of skip, adding massive amounts
of additional noise to igt test runs.

Make sure we don't try to disable fbc when it's off already.

V2: Squash in additional WARN_ON suggestion from Chris.

Cc: Paulo Zanoni <paulo.r.zanoni@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20170811072327.4335-1-daniel.vetter@ffwll.ch
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/gpu/drm/i915/intel_fbc.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/drivers/gpu/drm/i915/intel_fbc.c
+++ b/drivers/gpu/drm/i915/intel_fbc.c
@@ -461,6 +461,8 @@ static void intel_fbc_schedule_activatio
 	struct intel_fbc_work *work = &fbc->work;
 
 	WARN_ON(!mutex_is_locked(&fbc->lock));
+	if (WARN_ON(!fbc->enabled))
+		return;
 
 	if (drm_crtc_vblank_get(&crtc->base)) {
 		DRM_ERROR("vblank not available for FBC on pipe %c\n",
@@ -1216,7 +1218,7 @@ static void intel_fbc_underrun_work_fn(s
 	mutex_lock(&fbc->lock);
 
 	/* Maybe we were scheduled twice. */
-	if (fbc->underrun_detected)
+	if (fbc->underrun_detected || !fbc->enabled)
 		goto out;
 
 	DRM_DEBUG_KMS("Disabling FBC due to FIFO underrun.\n");