[bug report] drm/msm/a6xx: Fix llcc configuration for a660 gpu

[Dan Carpenter]

[ Nathan, it turns out that Smatch has been broken with regards to
  uninitialized variables for a while so I'm going through my backlog
  of warnings.  No idea if you already reported this one.

  - dan]

Hello Akhil P Oommen,

The patch a6f24383f6c0: "drm/msm/a6xx: Fix llcc configuration for
a660 gpu" from Jul 30, 2021, leads to the following Smatch static
checker warning:

	drivers/gpu/drm/msm/adreno/a6xx_gpu.c:1480 a6xx_llc_activate()
	error: uninitialized symbol 'gpu_scid'.

drivers/gpu/drm/msm/adreno/a6xx_gpu.c
    1423 static void a6xx_llc_activate(struct a6xx_gpu *a6xx_gpu)
    1424 {
    1425         struct adreno_gpu *adreno_gpu = &a6xx_gpu->base;
    1426         struct msm_gpu *gpu = &adreno_gpu->base;
    1427         u32 gpu_scid, cntl1_regval = 0;
                 ^^^^^^^^^^^^

    1428 
    1429         if (IS_ERR(a6xx_gpu->llc_mmio))
    1430                 return;
    1431 
    1432         if (!llcc_slice_activate(a6xx_gpu->llc_slice)) {
    1433                 gpu_scid = llcc_get_slice_id(a6xx_gpu->llc_slice);
                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

    1434 
    1435                 gpu_scid &= 0x1f;
    1436                 cntl1_regval = (gpu_scid << 0) | (gpu_scid << 5) | (gpu_scid << 10) |
    1437                                (gpu_scid << 15) | (gpu_scid << 20);
    1438         }
    1439 
    1440         /*
    1441          * For targets with a MMU500, activate the slice but don't program the
    1442          * register.  The XBL will take care of that.
    1443          */
    1444         if (!llcc_slice_activate(a6xx_gpu->htw_llc_slice)) {
    1445                 if (!a6xx_gpu->have_mmu500) {
    1446                         u32 gpuhtw_scid = llcc_get_slice_id(a6xx_gpu->htw_llc_slice);
    1447 
    1448                         gpuhtw_scid &= 0x1f;
    1449                         cntl1_regval |= FIELD_PREP(GENMASK(29, 25), gpuhtw_scid);
    1450                 }
    1451         }
    1452 
    1453         if (!cntl1_regval)
    1454                 return;
    1455 
    1456         /*
    1457          * Program the slice IDs for the various GPU blocks and GPU MMU
    1458          * pagetables
    1459          */
    1460         if (!a6xx_gpu->have_mmu500) {
    1461                 a6xx_llc_write(a6xx_gpu,
    1462                         REG_A6XX_CX_MISC_SYSTEM_CACHE_CNTL_1, cntl1_regval);
    1463 
    1464                 /*
    1465                  * Program cacheability overrides to not allocate cache
    1466                  * lines on a write miss
    1467                  */
    1468                 a6xx_llc_rmw(a6xx_gpu,
    1469                         REG_A6XX_CX_MISC_SYSTEM_CACHE_CNTL_0, 0xF, 0x03);
    1470                 return;
    1471         }
    1472 
    1473         gpu_rmw(gpu, REG_A6XX_GBIF_SCACHE_CNTL1, GENMASK(24, 0), cntl1_regval);
    1474 
    1475         /* On A660, the SCID programming for UCHE traffic is done in
    1476          * A6XX_GBIF_SCACHE_CNTL0[14:10]
    1477          */
    1478         if (adreno_is_a660_family(adreno_gpu))
    1479                 gpu_rmw(gpu, REG_A6XX_GBIF_SCACHE_CNTL0, (0x1f << 10) |
--> 1480                         (1 << 8), (gpu_scid << 10) | (1 << 8));
                                            ^^^^^^^^^^^^^^
Uninitialized if llcc_slice_activate() failed.

    1481 }

regards,
dan carpenter