[Intel-gfx] [PATCH] drm/i915: Disable primary plane if we fail to reconstruct BIOS fb

[Matt Roper]

If we fail to reconstruct the BIOS fb (e.g., because the FB is too
large), we'll be left with plane state that indicates the primary plane
is visible yet has a NULL fb.  This mismatch causes problems later on
(e.g., for the watermark code).  Since we've failed to reconstruct the
BIOS FB, the best solution is to just disable the primary plane and
pretend the BIOS never had it enabled.

Cc: Daniel Vetter <daniel at ffwll.ch>
Cc: Ville Syrjälä <ville.syrjala at intel.com>
Signed-off-by: Matt Roper <matthew.d.roper at intel.com>
---
Ville indicated that it might also be worth dropping the BIOS FB size test we
have today.  I'm not sure what the status of FBC is today (which I believe is
why we have the size check), so we should probably wait for Paulo to weigh in
on that part and potentially follow up with an additional patch.

 drivers/gpu/drm/i915/intel_display.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 68fb449..ed659e2 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -2597,6 +2597,8 @@ intel_find_initial_plane_obj(struct intel_crtc *intel_crtc,
 	struct drm_i915_gem_object *obj;
 	struct drm_plane *primary = intel_crtc->base.primary;
 	struct drm_plane_state *plane_state = primary->state;
+	struct drm_crtc_state *crtc_state = intel_crtc->base.state;
+	struct intel_plane *intel_plane = to_intel_plane(primary);
 	struct drm_framebuffer *fb;
 
 	if (!plane_config->fb)
@@ -2633,6 +2635,17 @@ intel_find_initial_plane_obj(struct intel_crtc *intel_crtc,
 		}
 	}
 
+	/*
+	 * We've failed to reconstruct the BIOS FB.  Current display state
+	 * indicates that the primary plane is visible, but has a NULL FB,
+	 * which will lead to problems later if we don't fix it up.  The
+	 * simplest solution is to just disable the primary plane now and
+	 * pretend the BIOS never had it enabled.
+	 */
+	to_intel_plane_state(plane_state)->visible = false;
+	crtc_state->plane_mask &= ~(1 << drm_plane_index(primary));
+	intel_plane->disable_plane(primary, &intel_crtc->base);
+
 	return;
 
 valid_fb:
-- 
2.1.4