[bug report] drm: Add helpers to kick off self refresh mode in drivers

[Dan Carpenter]

Hello Sean Paul,

The patch 1452c25b0e60: "drm: Add helpers to kick off self refresh
mode in drivers" from Jun 12, 2019, leads to the following static
checker warning:

	drivers/gpu/drm/drm_self_refresh_helper.c:118 drm_self_refresh_helper_entry_work()
	error: we previously assumed 'state' could be null (see line 77)

drivers/gpu/drm/drm_self_refresh_helper.c
    60  static void drm_self_refresh_helper_entry_work(struct work_struct *work)
    61  {
    62          struct drm_self_refresh_data *sr_data = container_of(
    63                                  to_delayed_work(work),
    64                                  struct drm_self_refresh_data, entry_work);
    65          struct drm_crtc *crtc = sr_data->crtc;
    66          struct drm_device *dev = crtc->dev;
    67          struct drm_modeset_acquire_ctx ctx;
    68          struct drm_atomic_state *state;
    69          struct drm_connector *conn;
    70          struct drm_connector_state *conn_state;
    71          struct drm_crtc_state *crtc_state;
    72          int i, ret;
    73  
    74          drm_modeset_acquire_init(&ctx, 0);
    75  
    76          state = drm_atomic_state_alloc(dev);
    77          if (!state) {
    78                  ret = -ENOMEM;
    79                  goto out;
                        ^^^^^^^^
The allocation failed.

    80          }
    81  
    82  retry:
    83          state->acquire_ctx = &ctx;
    84  
    85          crtc_state = drm_atomic_get_crtc_state(state, crtc);
    86          if (IS_ERR(crtc_state)) {
    87                  ret = PTR_ERR(crtc_state);
    88                  goto out;
    89          }
    90  
    91          if (!crtc_state->enable)
    92                  goto out;
    93  
    94          ret = drm_atomic_add_affected_connectors(state, crtc);
    95          if (ret)
    96                  goto out;
    97  
    98          for_each_new_connector_in_state(state, conn, conn_state, i) {
    99                  if (!conn_state->self_refresh_aware)
   100                          goto out;
   101          }
   102  
   103          crtc_state->active = false;
   104          crtc_state->self_refresh_active = true;
   105  
   106          ret = drm_atomic_commit(state);
   107          if (ret)
   108                  goto out;
   109  
   110  out:
   111          if (ret == -EDEADLK) {
   112                  drm_atomic_state_clear(state);
   113                  ret = drm_modeset_backoff(&ctx);
   114                  if (!ret)
   115                          goto retry;
   116          }
   117  
   118          drm_atomic_state_put(state);
                                     ^^^^^
NULL dereference.

   119          drm_modeset_drop_locks(&ctx);
   120          drm_modeset_acquire_fini(&ctx);
   121  }

regards,
dan carpenter