[PATCH stable-4.14 3/3] drm/i915: Fix deadlock in i830_disable_pipe()

[Ville Syrjala <ville.syrjala@linux.intel.com>]

From: Ville Syrjälä <ville.syrjala@linux.intel.com>

i830_disable_pipe() gets called from the power well code, and thus
we're already holding the power domain mutex. That means we can't
call plane->get_hw_state() as it will also try to grab the
same mutex and will thus deadlock.

Replace the assert_plane() calls (which calls ->get_hw_state()) with
just raw register reads in i830_disable_pipe(). As a bonus we can
now get a warning if plane C is enabled even though we don't even
expose it as a drm plane.

v2: Do a separate WARN_ON() for each plane (Chris)

Cc: <stable@vger.kernel.org> # 4.14
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Fixes: d87ce7640295 ("drm/i915: Add .get_hw_state() method for planes")
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171129125411.29055-1-ville.syrjala@linux.intel.com
(cherry picked from commit 5816d9cbc0a0fbf232fe297cefcb85361a3cde90)
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
(cherry picked from commit 4488496d58200c7511842e049a4cc891d928da56)
---
 drivers/gpu/drm/i915/intel_display.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 751b0f0582bc..46485692db48 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -14717,8 +14717,11 @@ void i830_disable_pipe(struct drm_i915_private *dev_priv, enum pipe pipe)
 	DRM_DEBUG_KMS("disabling pipe %c due to force quirk\n",
 		      pipe_name(pipe));
 
-	assert_planes_disabled(intel_get_crtc_for_pipe(dev_priv, PIPE_A));
-	assert_planes_disabled(intel_get_crtc_for_pipe(dev_priv, PIPE_B));
+	WARN_ON(I915_READ(DSPCNTR(PLANE_A)) & DISPLAY_PLANE_ENABLE);
+	WARN_ON(I915_READ(DSPCNTR(PLANE_B)) & DISPLAY_PLANE_ENABLE);
+	WARN_ON(I915_READ(DSPCNTR(PLANE_C)) & DISPLAY_PLANE_ENABLE);
+	WARN_ON(I915_READ(CURCNTR(PIPE_A)) & CURSOR_MODE);
+	WARN_ON(I915_READ(CURCNTR(PIPE_B)) & CURSOR_MODE);
 
 	I915_WRITE(PIPECONF(pipe), 0);
 	POSTING_READ(PIPECONF(pipe));
-- 
2.13.6