From: Jisheng Zhang <jisheng.zh...@synaptics.com> Date: Mon, 27 Jul 2020 19:53:14 +0800
> @@ -3651,7 +3651,8 @@ static void mvneta_stop_dev(struct mvneta_port *pp) > > set_bit(__MVNETA_DOWN, &pp->state); > > - if (device_may_wakeup(&pp->dev->dev)) > + if (device_may_wakeup(&pp->dev->dev) && > + pp->pkt_size == MVNETA_RX_PKT_SIZE(pp->dev->mtu)) > phylink_speed_down(pp->phylink, false); > This is too much for me. You shouldn't have to shut down the entire device and take it back up again just to change the MTU. Unfortunately, this is a common pattern in many drivers and it is very dangerous to take this lazy path of just doing "stop/start" around the MTU change. It means you can't recover from partial failures properly, f.e. recovering from an inability to allocate queue resources for the new MTU. To solve this properly, you must restructure the MTU change such that is specifically stops the necessary and only the units of the chip necessary to change the MTU. It should next try to allocate the necessary resources to satisfy the MTU change, keeping the existing resources allocated in case of failure. Then, only is all resources are successfully allocated, it should commit the MTU change fully and without errors. Then none of these link flapping issues are even possible.
