[Intel-gfx] [PATCH] drm/i915: Do not attempt to re-enable an unconnected primary plane

[Chris Wilson]

Due to user fudging (for instance using video=VGA-1:e with FBDEV=n) we can
attempt to reset an inconsistent CRTC that is marked as active but has
no assigned fb. It would be wise to fix this earlier, but the long
term plan is to have primary and secondary planes associated with a
CRTC, in which crtc->fb being NULL will be expected. So for a quick
short term fix with pretensions of grandeur, just check for a NULL fb
during GPU reset and ignore the plane restoration.

This fixes a potential hard hang (a panic in the panic handler)
following a GPU hang.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
---
 drivers/gpu/drm/i915/intel_display.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 61d48bcf6174..e7d6f55d45de 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -2243,7 +2243,7 @@ void intel_display_handle_reset(struct drm_device *dev)
 		struct intel_crtc *intel_crtc = to_intel_crtc(crtc);
 
 		mutex_lock(&crtc->mutex);
-		if (intel_crtc->active)
+		if (intel_crtc->active && crtc->fb)
 			dev_priv->display.update_plane(crtc, crtc->fb,
 						       crtc->x, crtc->y);
 		mutex_unlock(&crtc->mutex);
-- 
1.8.4.4