Re: [PATCH net] net: phy: Avoid multiple suspends

[Florian Fainelli]

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@xxxxxxxxxxxxx> wrote:
>> From: Florian Fainelli <f.fainelli@xxxxxxxxx>
>> 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@xxxxxxxxx>
>>
>> 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?

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;
-- 
Florian