netdev - Re: Regression in v4.20 with net phy soft reset changes

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Date:   Wed, 9 Jan 2019 22:54:57 +0100
From:   Heiner Kallweit <hkallweit1@...il.com>
To:     Tony Lindgren <tony@...mide.com>, Sekhar Nori <nsekhar@...com>
Cc:     Florian Fainelli <f.fainelli@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Andrew Lunn <andrew@...n.ch>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Chris Healy <cphealy@...il.com>,
        Clemens Gruber <clemens.gruber@...ruber.com>,
        Grygorii Strashko <grygorii.strashko@...com>,
        Ivan Khoronzhuk <ivan.khoronzhuk@...aro.org>,
        Keerthy <j-keerthy@...com>,
        Murali Karicheri <m-karicheri2@...com>,
        Rex Chang <rchang@...com>, Tero Kristo <t-kristo@...com>,
        WingMan Kwok <w-kwok2@...com>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-omap@...r.kernel.org
Subject: Re: Regression in v4.20 with net phy soft reset changes

On 09.01.2019 22:36, Tony Lindgren wrote:
> Hi,
> 
> * Heiner Kallweit <hkallweit1@...il.com> [190109 19:28]:
>> On 09.01.2019 20:06, Tony Lindgren wrote:
>>> Commit 6e2d85ec0559 ("net: phy: Stop with excessive soft reset") caused
>>> a regression where suspend resume cycle fails to bring up Ethernet on at
>>> least cpsw on am437x-sk-evm.
>>>
>> What kind of PHY and which PHY driver is used with this board?
>> I found one schematics of am437x where a KSZ9031RN PHY is used.
>> Is it the same on your board?
> 
> Yes that's the phy.
> 
>> As described in the commit message of this commit you would have
>> the option to implement the soft_reset callback in the PHY driver.
>> Can you try to add .soft_reset = genphy_soft_reset to the
>> KSZ9031 driver config in drivers/net/phy/micrel.c and check whether
>> it fixes the issue?
> 
> Yes that seems to work based on a quick test of five suspend
> resume cycles.
> 
> I wonder what all hardware this issue affects though?
> 
As one of few vendors Microchip publishes errata documentation
like this one for KSZ9031RNX:
http://ww1.microchip.com/downloads/en/DeviceDoc/80000692D.pdf
I wonder whether this is applicable for the PHY in our case and
whether the need for an extra soft reset is caused by one of
the mentioned issues.

> It's probably best that the network folks check what all
> hardare needs patching.
> 
> For TI hardware, Sekhar and TI network folks, can you guys
> please check the various TI SoCs for multiple suspend resume
> cycles with v5.0-rc1 and patch accordingly? See also below
> for something else to check, 10 seconds to resume a phy
> seems very long to me :)
> 
>>> Keerthy noticed this may not happen on the first resume, but usually
>>> happens after few suspend resume cycles. The most working suspend resume
>>> cycles I've seen with the commit above is three.
> ...
>>> Note that unrelated to the commit above, there may be other issues too
>>> as the cpsw phy LED seems to come on only after about five seconds with
>>> about total of 10 seconds before the Ethernet is up again.
> 
> Regards,
> 
> Tony
> 
Heiner