Re: Issue with RTL8111 NIC after upgrade to kernel 4.19

[Marc Dionne]

On Wed, Nov 21, 2018 at 6:28 PM Heiner Kallweit <hkallweit1@xxxxxxxxx> wrote:
>
> On 21.11.2018 22:53, Marc Dionne wrote:
> > On Wed, Nov 21, 2018 at 4:52 PM Heiner Kallweit <hkallweit1@xxxxxxxxx> 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.

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

Marc