[bug report] drm: zte: add overlay plane support

[Dan Carpenter]

Hello Shawn Guo,

The patch 4e986d3705df: "drm: zte: add overlay plane support" from
Nov 16, 2016, leads to the following static checker warning:

	drivers/gpu/drm/zte/zx_plane.c:170 zx_vl_rsz_setup()
	warn: always true condition '(fmt >= 0) => (0-u32max >= 0)'

drivers/gpu/drm/zte/zx_plane.c
   156  static void zx_vl_rsz_setup(struct zx_plane *zplane, uint32_t format,
   157                              u32 src_w, u32 src_h, u32 dst_w, u32 dst_h)
   158  {
   159          void __iomem *rsz = zplane->rsz;
   160          u32 src_chroma_w = src_w;
   161          u32 src_chroma_h = src_h;
   162          u32 fmt;
                ^^^^^^^
   163  
   164          /* Set up source and destination resolution */
   165          zx_writel(rsz + RSZ_SRC_CFG, RSZ_VER(src_h - 1) | RSZ_HOR(src_w - 1));
   166          zx_writel(rsz + RSZ_DEST_CFG, RSZ_VER(dst_h - 1) | RSZ_HOR(dst_w - 1));
   167  
   168          /* Configure data format for VL RSZ */
   169          fmt = zx_vl_rsz_get_fmt(format);
                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
If fmt is -EINVAL then don't we just want to return anyway?

   170          if (fmt >= 0)
   171                  zx_writel_mask(rsz + RSZ_VL_CTRL_CFG, RSZ_VL_FMT_MASK, fmt);
   172  
   173          /* Calculate Chroma height and width */
   174          if (fmt == RSZ_VL_FMT_YCBCR420) {
   175                  src_chroma_w = src_w >> 1;
   176                  src_chroma_h = src_h >> 1;
   177          } else if (fmt == RSZ_VL_FMT_YCBCR422) {
   178                  src_chroma_w = src_w >> 1;
   179          }
   180  
   181          /* Set up Luma and Chroma step registers */
   182          zx_writel(rsz + RSZ_VL_LUMA_HOR, rsz_step_value(src_w, dst_w));
   183          zx_writel(rsz + RSZ_VL_LUMA_VER, rsz_step_value(src_h, dst_h));
   184          zx_writel(rsz + RSZ_VL_CHROMA_HOR, rsz_step_value(src_chroma_w, dst_w));
   185          zx_writel(rsz + RSZ_VL_CHROMA_VER, rsz_step_value(src_chroma_h, dst_h));
   186  
   187          zx_vl_rsz_set_update(zplane);
   188  }

regards,
dan carpenter