diff --git a/drivers/gpu/drm/amd/amdgpu/gfx_v10_0.c b/drivers/gpu/drm/amd/amdgpu/gfx_v10_0.c
index 0597aeb..327b1f8 100644
--- a/drivers/gpu/drm/amd/amdgpu/gfx_v10_0.c
+++ b/drivers/gpu/drm/amd/amdgpu/gfx_v10_0.c
@@ -6871,8 +6871,12 @@ static int gfx_v10_0_kiq_init_register(struct amdgpu_ring *ring)
 	if (ring->use_doorbell) {
 		WREG32_SOC15(GC, 0, mmCP_MEC_DOORBELL_RANGE_LOWER,
 			(adev->doorbell_index.kiq * 2) << 2);
+		/* If GC has entered CGPG, ringing doorbell > first page doesn't
+		 * wakeup GC. Enlarge CP_MEC_DOORBELL_RANGE_UPPER to workaround
+		 * this issue.
+		 */
 		WREG32_SOC15(GC, 0, mmCP_MEC_DOORBELL_RANGE_UPPER,
-			(adev->doorbell_index.userqueue_end * 2) << 2);
+			(adev->doorbell.size - 4));
 	}
 
 	WREG32_SOC15(GC, 0, mmCP_HQD_PQ_DOORBELL_CONTROL,
diff --git a/drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c b/drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c
index 516467e..c09225d 100644
--- a/drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c
+++ b/drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c
@@ -3673,8 +3673,12 @@ static int gfx_v9_0_kiq_init_register(struct amdgpu_ring *ring)
 	if (ring->use_doorbell) {
 		WREG32_SOC15(GC, 0, mmCP_MEC_DOORBELL_RANGE_LOWER,
 					(adev->doorbell_index.kiq * 2) << 2);
+		/* If GC has entered CGPG, ringing doorbell > first page doesn't
+		 * wakeup GC. Enlarge CP_MEC_DOORBELL_RANGE_UPPER to workaround
+		 * this issue.
+		 */
 		WREG32_SOC15(GC, 0, mmCP_MEC_DOORBELL_RANGE_UPPER,
-					(adev->doorbell_index.userqueue_end * 2) << 2);
+					(adev->doorbell.size - 4));
 	}
 
 	WREG32_SOC15_RLC(GC, 0, mmCP_HQD_PQ_DOORBELL_CONTROL,