From: Shirish S <shirish.s@amd.com>
Date: Wed, 28 Feb 2018 12:14:58 +0530
Subject: drm/amd/display: disable CRTCs with NULL FB on their primary plane
 (V2)
Git-commit: 36cc549d59864b7161f0e23d710c1c4d1b9cf022
Patch-mainline: v4.16-rc5
References: FATE#326289 FATE#326079 FATE#326049 FATE#322398 FATE#326166

The below commit

"drm/atomic: Try to preserve the crtc enabled state in drm_atomic_remove_fb, v2"

introduces a slight behavioral change to rmfb. Instead of disabling a crtc
when the primary plane is disabled, it now preserves it.

This change leads to BUG hit while performing atomic commit on amd driver.

As a fix this patch ensures that we disable the CRTC's with NULL FB by returning
-EINVAL and hence triggering fall back to the old behavior and turning off the
crtc in atomic_remove_fb().

V2: Added error check for plane_state and removed sanity check for crtc.

Signed-off-by: Shirish S <shirish.s@amd.com>
Signed-off-by: Pratik Vishwakarma <Pratik.Vishwakarma@amd.com>
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Acked-by: Petr Tesarik <ptesarik@suse.com>
---
 drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c |   28 ++++++++++++++++++++++
 1 file changed, 28 insertions(+)

--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -4746,6 +4746,30 @@ static int dm_update_planes_state(struct
 	return ret;
 }
 
+static int dm_atomic_check_plane_state_fb(struct drm_atomic_state *state,
+					  struct drm_crtc *crtc)
+{
+	struct drm_plane *plane;
+	struct drm_crtc_state *crtc_state;
+
+	WARN_ON(!drm_atomic_get_new_crtc_state(state, crtc));
+
+	drm_for_each_plane_mask(plane, state->dev, crtc->state->plane_mask) {
+		struct drm_plane_state *plane_state =
+			drm_atomic_get_plane_state(state, plane);
+
+		if (IS_ERR(plane_state))
+			return -EDEADLK;
+
+		crtc_state = drm_atomic_get_crtc_state(plane_state->state, crtc);
+		if (crtc->primary == plane && crtc_state->active) {
+			if (!plane_state->fb)
+				return -EINVAL;
+		}
+	}
+	return 0;
+}
+
 static int amdgpu_dm_atomic_check(struct drm_device *dev,
 				  struct drm_atomic_state *state)
 {
@@ -4769,6 +4793,10 @@ static int amdgpu_dm_atomic_check(struct
 		goto fail;
 
 	for_each_oldnew_crtc_in_state(state, crtc, old_crtc_state, new_crtc_state, i) {
+		ret = dm_atomic_check_plane_state_fb(state, crtc);
+		if (ret)
+			goto fail;
+
 		if (!drm_atomic_crtc_needs_modeset(new_crtc_state) &&
 		    !new_crtc_state->color_mgmt_changed)
 			continue;