[bug report] drm/ingenic: Add support for the IPU

[dan.carpenter at oracle.com]

Hello Paul Cercueil,

The patch fc1acf317b01: "drm/ingenic: Add support for the IPU" from
Jul 16, 2020, leads to the following static checker warning:

	drivers/gpu/drm/ingenic/ingenic-drm-drv.c:232 ingenic_drm_crtc_atomic_check()
	error: potentially dereferencing uninitialized 'ipu_state'.

drivers/gpu/drm/ingenic/ingenic-drm-drv.c
   197  static int ingenic_drm_crtc_atomic_check(struct drm_crtc *crtc,
   198                                           struct drm_crtc_state *state)
   199  {
   200          struct ingenic_drm *priv = drm_crtc_get_priv(crtc);
   201          struct drm_plane_state *f1_state, *f0_state, *ipu_state;
   202          long rate;
   203  
   204          if (!drm_atomic_crtc_needs_modeset(state))
   205                  return 0;
   206  
   207          if (state->mode.hdisplay > priv->soc_info->max_width ||
   208              state->mode.vdisplay > priv->soc_info->max_height)
   209                  return -EINVAL;
   210  
   211          rate = clk_round_rate(priv->pix_clk,
   212                                state->adjusted_mode.clock * 1000);
   213          if (rate < 0)
   214                  return rate;
   215  
   216          if (priv->soc_info->has_osd) {
   217                  f1_state = drm_atomic_get_plane_state(state->state, &priv->f1);
   218                  f0_state = drm_atomic_get_plane_state(state->state, &priv->f0);
   219  
   220                  if (IS_ENABLED(CONFIG_DRM_INGENIC_IPU) && priv->ipu_plane) {

Do we need to check both the CONFIG and the priv->ipu_plane or would it
be sufficient to just check if (priv->ipu_plane) {?

   221                          ipu_state = drm_atomic_get_plane_state(state->state, priv->ipu_plane);
   222  
   223                          /* IPU and F1 planes cannot be enabled at the same time. */
   224                          if (f1_state->fb && ipu_state->fb) {
   225                                  dev_dbg(priv->dev, "Cannot enable both F1 and IPU\n");
   226                                  return -EINVAL;
   227                          }
   228                  }
   229  
   230                  /* If all the planes are disabled, we won't get a VBLANK IRQ */
   231                  priv->no_vblank = !f1_state->fb && !f0_state->fb &&
   232                                    !(priv->ipu_plane && ipu_state->fb);
                                            ^^^^^^^^^^^^^^^
Because here we're only checking "priv->ipu_plane".

   233          }
   234  
   235          return 0;
   236  }

regards,
dan carpenter