[Intel-gfx] [PATCH 1/9] 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>
---
With this patch, the rest of this series now runs without problems on Jani's
system where the regressions were originally reported.

Chris pointed out that this might also fix some of the other bugzillas we have
on older platforms where there's a GPU hang on failed FB takeover.  I don't
think I have any platforms that can reproduce those types of problems to
verify, but he listed candidate bugs as:

        https://bugs.freedesktop.org/show_bug.cgi?id=89319
        https://bugs.freedesktop.org/show_bug.cgi?id=87677
        https://bugs.freedesktop.org/show_bug.cgi?id=89146
        https://bugs.freedesktop.org/show_bug.cgi?id=91653

 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 4b21d5e..d03a235 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