Subject: Re: [PATCH net-next] net: dsa: mv88e6xxx: Add suspend/resume callbacks

From: Andrew Lunn <[email-masked]>
Date: Wed, 16 Jan 2019 16:56:51 +0100

On Wed, Jan 16, 2019 at 04:34:19PM +0100, Miquel Raynal wrote:
> Bring S2RAM support to the mv88e6xxx DSA driver.
> 
> The content of the *_irq_poll() helper is moved in *_do_irq_poll() so
> that that the function can be called from the ->resume() callback
> without using the *work pointer.
> 
> +static int __maybe_unused mv88e6xxx_suspend(struct device *dev)
> +{
> +	struct dsa_switch *ds = dev_get_drvdata(dev);
> +	struct mv88e6xxx_chip *chip = ds->priv;
> +
> +	kthread_cancel_delayed_work_sync(&chip->irq_poll_work);
> +
> +	return dsa_switch_suspend(ds);
> +}

Hi Miquel

I don't think this is sufficient. You are leaving the switch itself
running. It will still be forwarding frames. And since the host is
shutdown, there is nothing doing spanning tree protocol. So you are
likely to cause loops in your network.

Take a look at bcm_sf2:

static int bcm_sf2_sw_suspend(struct dsa_switch *ds)
{
        struct bcm_sf2_priv *priv = bcm_sf2_to_priv(ds);
        unsigned int port;

        bcm_sf2_intr_disable(priv);

        /* Disable all ports physically present including the IMP
         * port, the other ones have already been disabled during
         * bcm_sf2_sw_setup
         */
        for (port = 0; port < DSA_MAX_PORTS; port++) {
                if (dsa_is_user_port(ds, port) || dsa_is_cpu_port(ds, port))
                        bcm_sf2_port_disable(ds, port, NULL);
        }

        return 0;
}

qca8k does something similar.

	Andrew