drm/amdgpu/gmc10: remove dummy read workaround for newer chips

Sienna Cichlid and newer have a hw fix so no longer require
the workaround.
Reviewed-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Hawking Zhang <Hawking.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/gmc_v10_0.c

@@ -107,7 +107,8 @@ static int gmc_v10_0_process_interrupt(struct amdgpu_device *adev,
 		 * be updated to avoid reading an incorrect value due to
 		 * the new fast GRBM interface.
 		 */
-		if (entry->vmid_src == AMDGPU_GFXHUB_0)
+		if ((entry->vmid_src == AMDGPU_GFXHUB_0) &&
+		    (adev->asic_type < CHIP_SIENNA_CICHLID))
 			RREG32(hub->vm_l2_pro_fault_status);
 
 		status = RREG32(hub->vm_l2_pro_fault_status);
@@ -232,7 +233,8 @@ static void gmc_v10_0_flush_vm_hub(struct amdgpu_device *adev, uint32_t vmid,
 	 * Issue a dummy read to wait for the ACK register to be cleared
 	 * to avoid a false ACK due to the new fast GRBM interface.
 	 */
-	if (vmhub == AMDGPU_GFXHUB_0)
+	if ((vmhub == AMDGPU_GFXHUB_0) &&
+	    (adev->asic_type < CHIP_SIENNA_CICHLID))
 		RREG32_NO_KIQ(hub->vm_inv_eng0_req + hub->eng_distance * eng);
 
 	/* Wait for ACK with a delay.*/