drm/amdgpu:No action when VCN PG state is unchanged

When VCN PG state is unchanged, it is unnecessary to reset power
gate state
Signed-off-by: NJames Zhu <James.Zhu@amd.com>
Acked-by: NAlex Deucher <alexander.deucher@amd.com>
Acked-by: NChristian König <christian.koenig@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/amdgpu_vcn.h

@@ -69,6 +69,7 @@ struct amdgpu_vcn {
 	struct amdgpu_ring	ring_jpeg;
 	struct amdgpu_irq_src	irq;
 	unsigned		num_enc_rings;
+	enum amd_powergating_state cur_state;
 };
 
 int amdgpu_vcn_sw_init(struct amdgpu_device *adev);

drivers/gpu/drm/amd/amdgpu/vcn_v1_0.c

@@ -1633,12 +1633,20 @@ static int vcn_v1_0_set_powergating_state(void *handle,
 	 * revisit this when there is a cleaner line between
 	 * the smc and the hw blocks
 	 */
+	int ret;
 	struct amdgpu_device *adev = (struct amdgpu_device *)handle;
 
+	if(state == adev->vcn.cur_state)
+		return 0;
+
 	if (state == AMD_PG_STATE_GATE)
-		return vcn_v1_0_stop(adev);
+		ret = vcn_v1_0_stop(adev);
 	else
-		return vcn_v1_0_start(adev);
+		ret = vcn_v1_0_start(adev);
+
+	if(!ret)
+		adev->vcn.cur_state = state;
+	return ret;
 }
 
 static const struct amd_ip_funcs vcn_v1_0_ip_funcs = {