drm/msm/dpu: Fix variable dereferenced before check

Fixes the following smatch warning:

drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_wb.c:261
dpu_encoder_phys_wb_atomic_check() warn: variable dereferenced before check 'conn_state'

Fixes: d7d0e73f7de3 ("drm/msm/dpu: introduce the dpu_encoder_phys_* for writeback")
Signed-off-by: sunliming <sunliming@kylinos.cn>
Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Abhinav Kumar <quic_abhinavk@quicinc.com>
Patchwork: https://patchwork.freedesktop.org/patch/490850/
Link: https://lore.kernel.org/r/20220623012707.453972-1-sunliming@kylinos.cn
Signed-off-by: Abhinav Kumar <quic_abhinavk@quicinc.com>

diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_wb.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_wb.c
index 59da348..0ec809a 100644 (file)
--- a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_wb.c
+++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_wb.c
@@ -252,11 +252,6 @@ static int dpu_encoder_phys_wb_atomic_check(
        DPU_DEBUG("[atomic_check:%d, \"%s\",%d,%d]\n",
                        phys_enc->wb_idx, mode->name, mode->hdisplay, mode->vdisplay);
 
-       if (!conn_state->writeback_job || !conn_state->writeback_job->fb)
-               return 0;
-
-       fb = conn_state->writeback_job->fb;
-
        if (!conn_state || !conn_state->connector) {
                DPU_ERROR("invalid connector state\n");
                return -EINVAL;
@@ -267,6 +262,11 @@ static int dpu_encoder_phys_wb_atomic_check(
                return -EINVAL;
        }
 
+       if (!conn_state->writeback_job || !conn_state->writeback_job->fb)
+               return 0;
+
+       fb = conn_state->writeback_job->fb;
+
        DPU_DEBUG("[fb_id:%u][fb:%u,%u]\n", fb->base.id,
                        fb->width, fb->height);