From: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Date: Wed, 1 Nov 2017 16:04:33 +0100
Subject: drm/atomic: Try to preserve the crtc enabled state in
 drm_atomic_remove_fb, v2.
Git-commit: 846c7dfc1193eb2f9866fe2fa0ae7d45c72f95b9
Patch-mainline: v4.16-rc1
References: FATE#326289 FATE#326079 FATE#326049 FATE#322398 FATE#326166

This introduces a slight behavioral change to rmfb. Instead of
disabling a crtc when the primary plane is disabled, we try to
preserve it.

Apart from old versions of the vmwgfx xorg driver, there is
nothing depending on rmfb disabling a crtc.

Vmwgfx' and simple kms helper atomic implementation rejects CRTC
enabled without plane, so we can do this safely.

If the atomic commit is rejected by the driver then we will still
fall back to the old behavior and turn off the crtc.

Changes since v1:
- Restart completely when rmfb with crtc on fails (Sean Paul).

Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Sean Paul <seanpaul@chromium.org>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@ubuntu.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171101150433.10777-1-maarten.lankhorst@linux.intel.com
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Acked-by: Petr Tesarik <ptesarik@suse.com>
---
 drivers/gpu/drm/drm_framebuffer.c |   23 +++++++++++++++++------
 1 file changed, 17 insertions(+), 6 deletions(-)

--- a/drivers/gpu/drm/drm_framebuffer.c
+++ b/drivers/gpu/drm/drm_framebuffer.c
@@ -767,14 +767,18 @@ static int atomic_remove_fb(struct drm_f
 	struct drm_plane *plane;
 	struct drm_connector *conn;
 	struct drm_connector_state *conn_state;
-	int i, ret = 0;
+	int i, ret;
 	unsigned plane_mask;
+	bool disable_crtcs = false;
 
-	state = drm_atomic_state_alloc(dev);
-	if (!state)
-		return -ENOMEM;
-
+retry_disable:
 	drm_modeset_acquire_init(&ctx, 0);
+
+	state = drm_atomic_state_alloc(dev);
+	if (!state) {
+		ret = -ENOMEM;
+		goto out;
+	}
 	state->acquire_ctx = &ctx;
 
 retry:
@@ -795,7 +799,7 @@ retry:
 			goto unlock;
 		}
 
-		if (plane_state->crtc->primary == plane) {
+		if (disable_crtcs && plane_state->crtc->primary == plane) {
 			struct drm_crtc_state *crtc_state;
 
 			crtc_state = drm_atomic_get_existing_crtc_state(state, plane_state->crtc);
@@ -820,6 +824,7 @@ retry:
 		plane->old_fb = plane->fb;
 	}
 
+	/* This list is only filled when disable_crtcs is set. */
 	for_each_new_connector_in_state(state, conn, conn_state, i) {
 		ret = drm_atomic_set_crtc_for_connector(conn_state, NULL);
 
@@ -842,9 +847,15 @@ unlock:
 
 	drm_atomic_state_put(state);
 
+out:
 	drm_modeset_drop_locks(&ctx);
 	drm_modeset_acquire_fini(&ctx);
 
+	if (ret == -EINVAL && !disable_crtcs) {
+		disable_crtcs = true;
+		goto retry_disable;
+	}
+
 	return ret;
 }