netdev - Re: [PATCH net-next v2 0/2] net: phy: improve PHY suspend/resume

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Message-ID: <20180523220418.GB5128@lunn.ch>
Date:   Thu, 24 May 2018 00:04:18 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Heiner Kallweit <hkallweit1@...il.com>
Cc:     Florian Fainelli <f.fainelli@...il.com>,
        David Miller <davem@...emloft.net>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next v2 0/2] net: phy: improve PHY suspend/resume

On Wed, May 23, 2018 at 10:15:29PM +0200, Heiner Kallweit wrote:
> I have the issue that suspending the MAC-integrated PHY gives an
> error during system suspend. The sequence is:
> 
> 1. unconnected PHY/MAC are runtime-suspended already
> 2. system suspend commences
> 3. mdio_bus_phy_suspend is called
> 4. suspend callback of the network driver is called (implicitly
>    MAC/PHY are runtime-resumed before)
> 5. suspend callback suspends MAC/PHY
> 
> The problem occurs in step 3. phy_suspend() fails because the MDIO
> bus isn't accessible due to the chip being runtime-suspended.

I think you are fixing the wrong problem. I've had the same with the
FEC driver. I fixed it by making the MDIO operations runtime-suspend
aware:

commit 8fff755e9f8d0f70a595e79f248695ce6aef5cc3
Author: Andrew Lunn <andrew@...n.ch>
Date:   Sat Jul 25 22:38:02 2015 +0200

    net: fec: Ensure clocks are enabled while using mdio bus
    
    When a switch is attached to the mdio bus, the mdio bus can be used
    while the interface is not open. If the IPG clock is not enabled, MDIO
    reads/writes will simply time out.
    
    Add support for runtime PM to control this clock. Enable/disable this
    clock using runtime PM, with open()/close() and mdio read()/write()
    function triggering runtime PM operations. Since PM is optional, the
    IPG clock is enabled at probe and is no longer modified by
    fec_enet_clk_enable(), thus if PM is not enabled in the kernel, it is
    guaranteed the clock is running when MDIO operations are performed.

Don't copy this patch 1:1. I introduced a few bugs which took a while
to be shaken out :-(

   Andrew