drm/amd/amdgpu: Add rev_id workaround logic for SRIOV setup

- When we are under SRIOV setup, the rev_id cannot be read
  properly. Therefore, we will return default value for it
Signed-off-by: Bokun Zhang <Bokun.Zhang@amd.com>
Reviewed-by: Monk Liu <monk.liu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/nbio_v2_3.c

@@ -53,8 +53,17 @@ static void nbio_v2_3_remap_hdp_registers(struct amdgpu_device *adev)
 
 static u32 nbio_v2_3_get_rev_id(struct amdgpu_device *adev)
 {
-	u32 tmp = RREG32_SOC15(NBIO, 0, mmRCC_DEV0_EPF0_STRAP0);
+	u32 tmp;
 
+	/*
+	 * guest vm gets 0xffffffff when reading RCC_DEV0_EPF0_STRAP0,
+	 * therefore we force rev_id to 0 (which is the default value)
+	 */
+	if (amdgpu_sriov_vf(adev)) {
+		return 0;
+	}
+
+	tmp = RREG32_SOC15(NBIO, 0, mmRCC_DEV0_EPF0_STRAP0);
 	tmp &= RCC_DEV0_EPF0_STRAP0__STRAP_ATI_REV_ID_DEV0_F0_MASK;
 	tmp >>= RCC_DEV0_EPF0_STRAP0__STRAP_ATI_REV_ID_DEV0_F0__SHIFT;