netdev - Re: [Intel-wired-lan] [PATCH] e1000e: Make speed detection on hotplugging cable more reliable

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Date:   Mon, 15 Jul 2019 17:21:04 +0800
From:   Kai Heng Feng <kai.heng.feng@...onical.com>
To:     Paul Menzel <pmenzel@...gen.mpg.de>
Cc:     Jeff Kirsher <jeffrey.t.kirsher@...el.com>, netdev@...r.kernel.org,
        intel-wired-lan@...ts.osuosl.org, linux-kernel@...r.kernel.org
Subject: Re: [Intel-wired-lan] [PATCH] e1000e: Make speed detection on
 hotplugging cable more reliable

at 5:06 PM, Paul Menzel <pmenzel@...gen.mpg.de> wrote:

> Dear Kai Heng,
>
>
> (with or without hyphen?)
>
> On 7/15/19 11:00 AM, Kai Heng Feng wrote:
>> at 4:52 PM, Paul Menzel <pmenzel@...gen.mpg.de> wrote:
>
>>> On 7/15/19 10:43 AM, Kai-Heng Feng wrote:
>>>> After hotplugging an 1Gbps ethernet cable with 1Gbps link partner, the
>>>> MII_BMSR may reports 10Mbps, renders the network rather slow.
>>>
>>> s/may reports/may report/
>>> s/renders/rendering/
>>
>> Apparently English isn’t my mother tongue ;)
>
> No problem. Mine neither.
>
>>>> The issue has much lower fail rate after commit 59653e6497d1 ("e1000e:
>>>> Make watchdog use delayed work"), which esssentially introduces some
>>>
>>> essentially
>>
>> Ok.
>>
>>>> delay before running the watchdog task.
>>>>
>>>> But there's still a chance that the hotplugging event and the queued
>>>> watchdog task gets run at the same time, then the original issue can be
>>>> observed once again.
>>>>
>>>> So let's use mod_delayed_work() to add a deterministic 1 second delay
>>>> before running watchdog task, after an interrupt.
>>>
>>> I am not clear about the effects for the user. Could you elaborate
>>> please? Does the link now come up up to one second later?
>>
>> Yes, the link will be up on a fixed one second later.
>>
>> The delay varies between 0 to 2 seconds without this patch.
>
> Is there no other fix? Regarding booting a system fast (less than six
> seconds), a fixed one second delay is quite a regression on systems where
> it worked before.

This only affects when ethernet cable is hot plugged.

Kai-Heng

>
>>>> Signed-off-by: Kai-Heng Feng <kai.heng.feng@...onical.com>
>>>
>>> Any bug URL?
>>
>> If maintainers think it’s necessary then I’ll file one.
>
> Not necessary, if there is none. I thought you had one in Launchpad or so.
>
>
> Kind regards,
>
> Paul