[PATCH 2/2] drm/atomic-helper: log EINVAL cause in drm_atomic_helper_async_check()

[Simon Ser]

This can help figure out why the kernel returns EINVAL from
user-space.

Signed-off-by: Simon Ser <cont...@emersion.fr>
Cc: Daniel Vetter <daniel.vet...@ffwll.ch>
Cc: Lyude Paul <ly...@redhat.com>
---
 drivers/gpu/drm/drm_atomic_helper.c | 32 +++++++++++++++++++++++------
 1 file changed, 26 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/drm_atomic_helper.c 
b/drivers/gpu/drm/drm_atomic_helper.c
index fbdcca3047f2..63a0e1553408 100644
--- a/drivers/gpu/drm/drm_atomic_helper.c
+++ b/drivers/gpu/drm/drm_atomic_helper.c
@@ -1796,7 +1796,7 @@ int drm_atomic_helper_async_check(struct drm_device *dev,
        struct drm_plane_state *old_plane_state = NULL;
        struct drm_plane_state *new_plane_state = NULL;
        const struct drm_plane_helper_funcs *funcs;
-       int i, n_planes = 0;
+       int i, ret, n_planes = 0;
 
        for_each_new_crtc_in_state(state, crtc, crtc_state, i) {
                if (drm_atomic_crtc_needs_modeset(crtc_state))
@@ -1807,19 +1807,34 @@ int drm_atomic_helper_async_check(struct drm_device 
*dev,
                n_planes++;
 
        /* FIXME: we support only single plane updates for now */
-       if (n_planes != 1)
+       if (n_planes != 1) {
+               drm_dbg_atomic(dev,
+                              "only single plane async updates are 
supported\n");
                return -EINVAL;
+       }
 
        if (!new_plane_state->crtc ||
-           old_plane_state->crtc != new_plane_state->crtc)
+           old_plane_state->crtc != new_plane_state->crtc) {
+               drm_dbg_atomic(dev,
+                              "[PLANE:%d:%s] async update cannot change 
CRTC\n",
+                              plane->base.id, plane->name);
                return -EINVAL;
+       }
 
        funcs = plane->helper_private;
-       if (!funcs->atomic_async_update)
+       if (!funcs->atomic_async_update) {
+               drm_dbg_atomic(dev,
+                              "[PLANE:%d:%s] driver does not support async 
updates\n",
+                              plane->base.id, plane->name);
                return -EINVAL;
+       }
 
-       if (new_plane_state->fence)
+       if (new_plane_state->fence) {
+               drm_dbg_atomic(dev,
+                              "[PLANE:%d:%s] missing fence for async update\n",
+                              plane->base.id, plane->name);
                return -EINVAL;
+       }
 
        /*
         * Don't do an async update if there is an outstanding commit modifying
@@ -1834,7 +1849,12 @@ int drm_atomic_helper_async_check(struct drm_device *dev,
                return -EBUSY;
        }
 
-       return funcs->atomic_async_check(plane, state);
+       ret = funcs->atomic_async_check(plane, state);
+       if (ret != 0)
+               drm_dbg_atomic(dev,
+                              "[PLANE:%d:%s] driver async check failed",
+                              plane->base.id, plane->name);
+       return ret;
 }
 EXPORT_SYMBOL(drm_atomic_helper_async_check);
 
-- 
2.37.2