netdev - Re: Issue with RTL8111 NIC after upgrade to kernel 4.19

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Message-ID: <d38a9ed9-b801-5622-1d3a-1b9620ed9d8d@gmail.com>
Date:   Thu, 22 Nov 2018 19:17:19 +0100
From:   Heiner Kallweit <hkallweit1@...il.com>
To:     Marc Dionne <marc.c.dionne@...il.com>
Cc:     andrew@...n.ch, norbert.jurkeit@....de, nic_swsd@...ltek.com,
        Florian Fainelli <f.fainelli@...il.com>,
        David Miller <davem@...emloft.net>,
        netdev <netdev@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        michael.wiktowy@...il.com, jcline@...hat.com
Subject: Re: Issue with RTL8111 NIC after upgrade to kernel 4.19

On 22.11.2018 00:13, Marc Dionne wrote:
> On Wed, Nov 21, 2018 at 6:28 PM Heiner Kallweit <hkallweit1@...il.com> wrote:
>>
>> On 21.11.2018 22:53, Marc Dionne wrote:
>>> On Wed, Nov 21, 2018 at 4:52 PM Heiner Kallweit <hkallweit1@...il.com> wrote:
>>>>
>>>> On 21.11.2018 21:49, Heiner Kallweit wrote:
>>>>> On 21.11.2018 21:32, Heiner Kallweit wrote:
>>>>>> On 21.11.2018 21:20, Andrew Lunn wrote:
>>>>>>>> request_module() is supposed to be synchronous, however after some
>>>>>>>> reading this may not be 100% guaranteed. Maybe the module init
>>>>>>>> function on some systems isn't finished yet when request_module()
>>>>>>>> returns. As a result the genphy driver may be used instead of
>>>>>>>> the PHY version-specific driver.
>>>>>>>
>>>>>>> Hi Heiner
>>>>>>>
>>>>>>> That would be true for all PHYs i think. We would of noticed this
>>>>>>> problem with other systems using other PHY drivers.
>>>>>>>
>>>>>>>     Andrew
>>>>>>>
>>>>>> It could be a timing issue affecting certain systems only. At least
>>>>>> for now I don't have a good explanation why loading the module via
>>>>>> request_module() and loading it upfront manually makes a difference.
>>>>>>
>>>>>> One affected user just reported the PHY to be a RTL8211B. This is
>>>>>> what I expected, because this PHY crashes when writing to the MMD
>>>>>> registers (the MMD registers are used otherwise by this PHY).
>>>>>> See also commit 0231b1a074c6 ("net: phy: realtek: Use the dummy
>>>>>> stubs for MMD register access for rtl8211b").
>>>>>>
>>>>>> Let's see whether the other affected systems use the same PHY
>>>>>> version.
>>>>>>
>>>>> Next report is also about a RTL8211B and as I assumed:
>>>>> - W/o manually loading the realtek module the genphy driver is used
>>>>>   and network fails.
>>>>> - W/ manually loading the realtek module the proper RTL8211B PHY
>>>>>   driver is used and network works.
>>>>>
>>>>> So it seems that even after request_module() the PHY driver isn't
>>>>> yet available when device and driver are matched.
>>>>>
>>>>> If further reports support this (pre-)analysis, then indeed it
>>>>> seems to be a timing issue and a proper fix most likely is
>>>>> difficult. As a workaround I could imagine to add a delay loop
>>>>> after request_module() checking for a Realtek PHY driver via
>>>>> driver_find(). When adding one small delay after this we should
>>>>> be sufficiently sure that all Realtek PHY drivers are registered.
>>>>>
>>>> Uups, no. We talk about phylib here, not about the r8169 driver.
>>>> So we need a different solution.
>>>>
>>>>>> Heiner
>>>
>>> Thanks for the explanation, better than my crude attempt at
>>> understanding what was going on.
>>>
>>> If you have any proposed fixes or diagnostic patches based on current
>>> mainline I can quickly compile and test them here on an affected
>>> system.  It doesn't fail consistently for me (as others have
>>> reported), but that could be because it depends on the timing.
>>>
>>
>> Thanks for the offer. Can you try the following diagnostic patch
>> and check whether it helps?
>>
>> diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
>> index 55202a0ac..84f417f8b 100644
>> --- a/drivers/net/phy/phy_device.c
>> +++ b/drivers/net/phy/phy_device.c
>> @@ -607,6 +607,8 @@ struct phy_device *phy_device_create(struct mii_bus *bus, int addr, int phy_id,
>>          */
>>         request_module(MDIO_MODULE_PREFIX MDIO_ID_FMT, MDIO_ID_ARGS(phy_id));
>>
>> +       msleep(1000);
>> +
>>         device_initialize(&mdiodev->dev);
>>
>>         return dev;
> 
> I was not able to get it to fail with that extra delay; hard to be
> 100% sure but the network starts even when switching over from the
> distro kernel after a boot where network failed to start.
> 
Thanks a lot for testing. Could you please test also the following
as an alternative to the delay?

diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
index 55202a0ac..aeccb2323 100644
--- a/drivers/net/phy/phy_device.c
+++ b/drivers/net/phy/phy_device.c
@@ -2254,6 +2254,7 @@ int phy_driver_register(struct phy_driver *new_driver, struct module *owner)
        new_driver->mdiodrv.driver.probe = phy_probe;
        new_driver->mdiodrv.driver.remove = phy_remove;
        new_driver->mdiodrv.driver.owner = owner;
+       new_driver->mdiodrv.driver.probe_type = PROBE_FORCE_SYNCHRONOUS;

        retval = driver_register(&new_driver->mdiodrv.driver);
        if (retval) {

> There's a side issue that network startup is taking a full minute
> longer than it should, but that's possibly unrelated.
> 
> Marc
> 
Thanks, Heiner