BUG: amdgpu: NULL pointer dereference introduced in 5.9-rc1

[Dirk Gouders]

Commit c1cf79ca5ced46 (drm/amdgpu: use IP discovery table for renoir)
introduced a NULL pointer dereference when booting with
amdgpu.discovery=0.

For amdgpu.discovery=0 that commit effectively removed the call of
vega10_reg_base_init(adev), so I tested the correctness of the bisect
session by restoring that function call for amdgpu_discovery == 0 and with
that change, the NULL pointer dereference does not occur:

diff --git a/drivers/gpu/drm/amd/amdgpu/soc15.c b/drivers/gpu/drm/amd/amdgpu/soc15.c
index 84d811b6e48b..2e93c5e1e7e6 100644
--- a/drivers/gpu/drm/amd/amdgpu/soc15.c
+++ b/drivers/gpu/drm/amd/amdgpu/soc15.c
@@ -699,7 +699,8 @@ static void soc15_reg_base_init(struct amdgpu_device *adev)
                                         "fallback to legacy init method\n");
                                vega10_reg_base_init(adev);
                        }
-               }
+               } else
+                       vega10_reg_base_init(adev);
                break;
        case CHIP_VEGA20:
                vega20_reg_base_init(adev);

Dirk