[bug report] drm/msm/dpu: Skip trigger flush and start for CWB

[Dan Carpenter]

Hello Jessica Zhang,

This is a semi-automatic email about new static checker warnings.

Commit 8144d17a81d9 ("drm/msm/dpu: Skip trigger flush and start for
CWB") from Feb 14, 2025, leads to the following Smatch complaint:

    drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c:1672 _dpu_encoder_trigger_start()
    warn: variable dereferenced before check 'phys' (see line 1670)

drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
  1669	{
  1670		struct dpu_encoder_virt *dpu_enc = to_dpu_encoder_virt(phys->parent);
                                                                       ^^^^^^^^^^^^
Dereference

  1671	
  1672		if (!phys) {
                    ^^^^^

  1673			DPU_ERROR("invalid argument(s)\n");
  1674			return;

drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c:1814 _dpu_encoder_kickoff_phys()
error: we previously assumed 'dpu_enc->cur_master' could be null (see line 1807)

drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
  1805  
  1806          /* for split flush, combine pending flush masks and send to master */
  1807          if (pending_flush && dpu_enc->cur_master) {
                                     ^^^^^^^^^^^^^^^^^^^
Check for NULL

  1808                  _dpu_encoder_trigger_flush(
  1809                                  &dpu_enc->base,
  1810                                  dpu_enc->cur_master,
  1811                                  pending_flush);
  1812          }
  1813  
  1814          _dpu_encoder_trigger_start(dpu_enc->cur_master);
                                           ^^^^^^^^^^^^^^^^^^^
Unchecked dereference.  Although, I guess this will go away if we
fix the first warning.

  1815  

regards,
dan carpenter