[PATCH 3/3] drm/atomic: Try to preserve the crtc enabled state in drm_atomic_remove_fb.

[Maarten Lankhorst <maarten.lankhorst@linux.intel.com>]

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. Since vmwgfx is
a legacy driver we can safely only disable the plane with atomic.
In the conversion to atomic the driver will reject the config
without primary plane.

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

Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
---
 drivers/gpu/drm/drm_atomic.c | 22 ++++++++++++++++++++--
 1 file changed, 20 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
index 285e1c23e8c9..0d5b0065208e 100644
--- a/drivers/gpu/drm/drm_atomic.c
+++ b/drivers/gpu/drm/drm_atomic.c
@@ -2070,7 +2070,7 @@ int drm_atomic_remove_fb(struct drm_framebuffer *fb)
 	struct drm_connector *conn;
 	struct drm_connector_state *conn_state;
 	int i, ret = 0;
-	unsigned plane_mask;
+	unsigned plane_mask, disable_crtcs = false;
 
 	state = drm_atomic_state_alloc(dev);
 	if (!state)
@@ -2097,7 +2097,13 @@ int drm_atomic_remove_fb(struct drm_framebuffer *fb)
 			goto unlock;
 		}
 
-		if (plane_state->crtc->primary == plane) {
+		/*
+		 * Some drivers do not support keeping crtc active with the
+		 * primary plane disabled. If we fail to commit with -EINVAL
+		 * then we will try to perform the same commit but with all
+		 * crtc's disabled for primary planes as well.
+		 */
+		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);
@@ -2122,6 +2128,7 @@ int drm_atomic_remove_fb(struct drm_framebuffer *fb)
 		plane->old_fb = plane->fb;
 	}
 
+	/* This list is only not empty when disable_crtcs is set. */
 	for_each_connector_in_state(state, conn, conn_state, i) {
 		ret = drm_atomic_set_crtc_for_connector(conn_state, NULL);
 
@@ -2143,6 +2150,17 @@ int drm_atomic_remove_fb(struct drm_framebuffer *fb)
 
 	drm_atomic_state_put(state);
 
+	if (ret == -EINVAL && !disable_crtcs) {
+		disable_crtcs = true;
+
+		state = drm_atomic_state_alloc(dev);
+		if (state) {
+			state->acquire_ctx = &ctx;
+			goto retry;
+		}
+		ret = -ENOMEM;
+	}
+
 	drm_modeset_drop_locks(&ctx);
 	drm_modeset_acquire_fini(&ctx);
 
-- 
2.7.4

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