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

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Date:   Tue, 10 Mar 2020 15:16:34 +0100
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     David Miller <davem@...emloft.net>,
        Florian Fainelli <f.fainelli@...il.com>
Cc:     netdev <netdev@...r.kernel.org>,
        Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
        Andrew Lunn <andrew@...n.ch>,
        Heiner Kallweit <hkallweit1@...il.com>,
        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

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.

Gr{oetje,eeting}s,

                        Geert


--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds