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    SubjectRe: Regression in v4.20 with net phy soft reset changes
    * Sekhar Nori <nsekhar@ti.com> [190110 11:52]:
    > On 10/01/19 3:06 AM, Tony Lindgren wrote:
    > > 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
    >
    > Will do.

    OK thanks!

    > I don't see the link problem if I shift to 100Mps prior to the
    > plug/unplug experiment using ethtool. So looks like the problem is
    > restricted to Gigabit link only. Are you using Gigabit link too?

    Yes this is a Gigabit link.

    > I think we should patch drivers/net/phy/micrel.c to solve the
    > regression. Not sure of the root cause though. In the errata pointed to
    > by Heiner, there is "Module 6" which comes close to what we are seeing,
    > except it talks of a scenario where auto-negotiation is turned off 100M
    > link is used and we see the issue even with auto-neg on and in gigabit
    > mode. "Module 5" is also related to link failure, but is already worked
    > around in kernel with ksz9031_center_flp_timing().
    >
    > >>> 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.
    >
    > I don't quite see this problem on the AM437x GP EVM. I have seen gigabit
    > link takes quite some time (sometimes more than 10 seconds) on x15 EVM.
    > Not sure if the problem you are facing is related to gigabit too. If you
    > are using gigabit link, can you downgrade to 100MBps to check? Either
    > using a 100M only switch or by using ethtool on the EVM.
    >
    > $ ethtool -s eth0 speed 100 duplex full

    Yes this makes the 10 second resume latency go away on am437x-sk-evm
    here.

    Regards,

    Tony

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