netdev - Re: [PATCH v2] net: smsc911x: Quieten netif during suspend

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Date:   Wed, 13 Sep 2017 16:28:40 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Geert Uytterhoeven <geert+renesas@...der.be>,
        "David S . Miller" <davem@...emloft.net>,
        Steve Glendinning <steve.glendinning@...well.net>
Cc:     Andrew Lunn <andrew@...n.ch>, netdev@...r.kernel.org,
        linux-pm@...r.kernel.org, linux-renesas-soc@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] net: smsc911x: Quieten netif during suspend



On 09/13/2017 10:42 AM, Geert Uytterhoeven wrote:
> If the network interface is kept running during suspend, the net core
> may call net_device_ops.ndo_start_xmit() while the Ethernet device is
> still suspended, which may lead to a system crash.
> 
> E.g. on sh73a0/kzm9g and r8a73a4/ape6evm, the external Ethernet chip is
> driven by a PM controlled clock.  If the Ethernet registers are accessed
> while the clock is not running, the system will crash with an imprecise
> external abort.
> 
> As this is a race condition with a small time window, it is not so easy
> to trigger at will.  Using pm_test may increase your chances:
> 
>     # echo 0 > /sys/module/printk/parameters/console_suspend
>     # echo platform > /sys/power/pm_test
>     # echo mem > /sys/power/state
> 
> To fix this, make sure the network interface is quietened during
> suspend.
> 
> Signed-off-by: Geert Uytterhoeven <geert+renesas@...der.be>

Reviewed-by: Florian Fainelli <f.fainelli@...il.com>

You may want to take the opportunity to suspend the PHY device
(conversely resume it) if WoL is not enabled on this device.

Thanks!

> ---
> This is v2 of the series "[PATCH 0/2] net: Fix crashes due to activity
> during suspend", which degenerated into a single patch after commit
> ebc8254aeae34226 ("Revert "net: phy: Correctly process PHY_HALTED in
> phy_stop_machine()"") made "[PATCH 1/2] net: phy: Freeze PHY polling before
> suspending devices" no longer needed.
> 
> v2:
>   - Spelling s/quit/quiet/g.
> 
> No stacktrace is provided, as the imprecise external abort is usually
> reported from an innocent looking and unrelated function like
> __loop_delay(), cpu_idle_poll(), or arch_timer_read_counter_long().
> ---
>  drivers/net/ethernet/smsc/smsc911x.c | 15 ++++++++++++++-
>  1 file changed, 14 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/smsc/smsc911x.c b/drivers/net/ethernet/smsc/smsc911x.c
> index 0b6a39b003a4e188..012fb66eed8dd618 100644
> --- a/drivers/net/ethernet/smsc/smsc911x.c
> +++ b/drivers/net/ethernet/smsc/smsc911x.c
> @@ -2595,6 +2595,11 @@ static int smsc911x_suspend(struct device *dev)
>  	struct net_device *ndev = dev_get_drvdata(dev);
>  	struct smsc911x_data *pdata = netdev_priv(ndev);
>  
> +	if (netif_running(ndev)) {
> +		netif_stop_queue(ndev);
> +		netif_device_detach(ndev);
> +	}
> +
>  	/* enable wake on LAN, energy detection and the external PME
>  	 * signal. */
>  	smsc911x_reg_write(pdata, PMT_CTRL,
> @@ -2628,7 +2633,15 @@ static int smsc911x_resume(struct device *dev)
>  	while (!(smsc911x_reg_read(pdata, PMT_CTRL) & PMT_CTRL_READY_) && --to)
>  		udelay(1000);
>  
> -	return (to == 0) ? -EIO : 0;
> +	if (to == 0)
> +		return -EIO;
> +
> +	if (netif_running(ndev)) {
> +		netif_device_attach(ndev);
> +		netif_start_queue(ndev);
> +	}
> +
> +	return 0;
>  }
>  
>  static const struct dev_pm_ops smsc911x_pm_ops = {
> 

-- 
Florian