linux-kernel - Re: [PATCH net] net: phy: Avoid multiple suspends

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Date:   Tue, 10 Mar 2020 18:34:42 +0100
From:   Heiner Kallweit <hkallweit1@...il.com>
To:     Florian Fainelli <f.fainelli@...il.com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        David Miller <davem@...emloft.net>
Cc:     netdev <netdev@...r.kernel.org>,
        Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
        Andrew Lunn <andrew@...n.ch>,
        Russell King <linux@...linux.org.uk>, B38611@...escale.com,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>
Subject: Re: [PATCH net] net: phy: Avoid multiple suspends

On 10.03.2020 17:46, Florian Fainelli wrote:
> On 3/10/20 7:16 AM, Geert Uytterhoeven wrote:
>> Hi Florian, David,
>>
>> On Mon, Feb 24, 2020 at 5:59 AM David Miller <davem@...emloft.net> wrote:
>>> From: Florian Fainelli <f.fainelli@...il.com>
>>> Date: Thu, 20 Feb 2020 15:34:53 -0800
>>>
>>>> It is currently possible for a PHY device to be suspended as part of a
>>>> network device driver's suspend call while it is still being attached to
>>>> that net_device, either via phy_suspend() or implicitly via phy_stop().
>>>>
>>>> Later on, when the MDIO bus controller get suspended, we would attempt
>>>> to suspend again the PHY because it is still attached to a network
>>>> device.
>>>>
>>>> This is both a waste of time and creates an opportunity for improper
>>>> clock/power management bugs to creep in.
>>>>
>>>> Fixes: 803dd9c77ac3 ("net: phy: avoid suspending twice a PHY")
>>>> Signed-off-by: Florian Fainelli <f.fainelli@...il.com>
>>>
>>> Applied, and queued up for -stable, thanks Florian.
>>
>> This patch causes a regression on r8a73a4/ape6evm and sh73a0/kzm9g.
>> After resume from s2ram, Ethernet no longer works:
>>
>>         PM: suspend exit
>>         nfs: server aaa.bbb.ccc.ddd not responding, still trying
>>         ...
>>
>> Reverting commit 503ba7c6961034ff ("net: phy: Avoid multiple suspends")
>> fixes the issue.
>>
>> On both boards, an SMSC LAN9220 is connected to a power-managed local
>> bus.
>>
>> I added some debug code to check when the clock driving the local bus
>> is stopped and started, but I see no difference before/after.  Hence I
>> suspect the Ethernet chip is no longer reinitialized after resume.
> 
> Can you provide a complete log? Do you use the Generic PHY driver or a
> specialized one? Do you have a way to dump the registers at the time of
> failure and see if BMCR.PDOWN is still set somehow?
> 
Maybe reason for the misbehavior is that mdio_bus_phy_may_suspend() is
checked also in mdio_bus_phy_resume(), what's not very logical based
on the naming. The call to phy_resume() therefore may be skipped.


> Does the following help:
> 
> diff --git a/drivers/net/ethernet/smsc/smsc911x.c
> b/drivers/net/ethernet/smsc/smsc911x.c
> index 49a6a9167af4..df17190c76c0 100644
> --- a/drivers/net/ethernet/smsc/smsc911x.c
> +++ b/drivers/net/ethernet/smsc/smsc911x.c
> @@ -2618,6 +2618,7 @@ static int smsc911x_resume(struct device *dev)
>         if (netif_running(ndev)) {
>                 netif_device_attach(ndev);
>                 netif_start_queue(ndev);
> +               phy_resume(dev->phydev);
>         }
> 
>         return 0;
>