drm/amdgpu: Fix variable 'mca_funcs' dereferenced before NULL check in 'amdgpu_mca_smu_get_mca_entry()'

Fixes the below:

drivers/gpu/drm/amd/amdgpu/amdgpu_mca.c:377 amdgpu_mca_smu_get_mca_entry() warn: variable dereferenced before check 'mca_funcs' (see line 368)

357 int amdgpu_mca_smu_get_mca_entry(struct amdgpu_device *adev,
				     enum amdgpu_mca_error_type type,
358                                  int idx, struct mca_bank_entry *entry)
359 {
360         const struct amdgpu_mca_smu_funcs *mca_funcs =
						adev->mca.mca_funcs;
361         int count;
362
363         switch (type) {
364         case AMDGPU_MCA_ERROR_TYPE_UE:
365                 count = mca_funcs->max_ue_count;

mca_funcs is dereferenced here.

366                 break;
367         case AMDGPU_MCA_ERROR_TYPE_CE:
368                 count = mca_funcs->max_ce_count;

mca_funcs is dereferenced here.

369                 break;
370         default:
371                 return -EINVAL;
372         }
373
374         if (idx >= count)
375                 return -EINVAL;
376
377         if (mca_funcs && mca_funcs->mca_get_mca_entry)
	        ^^^^^^^^^

Checked too late!

Cc: Yang Wang <kevinyang.wang@amd.com>
Cc: Hawking Zhang <Hawking.Zhang@amd.com>
Cc: Christian König <christian.koenig@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Srinivasan Shanmugam <srinivasan.shanmugam@amd.com>
Reviewed-by: Yang Wang <kevinyang.wang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

Author: srishanm

drivers/gpu/drm/amd/amdgpu/amdgpu_mca.c

@@ -360,6 +360,9 @@ int amdgpu_mca_smu_get_mca_entry(struct amdgpu_device *adev, enum amdgpu_mca_err
 	const struct amdgpu_mca_smu_funcs *mca_funcs = adev->mca.mca_funcs;
 	int count;
 
+	if (!mca_funcs || !mca_funcs->mca_get_mca_entry)
+		return -EOPNOTSUPP;
+
 	switch (type) {
 	case AMDGPU_MCA_ERROR_TYPE_UE:
 		count = mca_funcs->max_ue_count;
@@ -374,10 +377,7 @@ int amdgpu_mca_smu_get_mca_entry(struct amdgpu_device *adev, enum amdgpu_mca_err
 	if (idx >= count)
 		return -EINVAL;
 
-	if (mca_funcs && mca_funcs->mca_get_mca_entry)
-		return mca_funcs->mca_get_mca_entry(adev, type, idx, entry);
-
-	return -EOPNOTSUPP;
+	return mca_funcs->mca_get_mca_entry(adev, type, idx, entry);
 }
 
 #if defined(CONFIG_DEBUG_FS)