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SubjectRe: How to fix WARN from drivers/base/dd.c in next-20200401 if CONFIG_MODULES=y?
Hi John,

On Thu, Apr 2, 2020 at 7:27 PM John Stultz <john.stultz@linaro.org> wrote:
> On Thu, Apr 2, 2020 at 3:17 AM Yoshihiro Shimoda
> <yoshihiro.shimoda.uh@renesas.com> wrote:
> >
> > I found an issue after applied the following patches:
> > ---
> > 64c775f driver core: Rename deferred_probe_timeout and make it global
> > 0e9f8d0 driver core: Remove driver_deferred_probe_check_state_continue()
> > bec6c0e pinctrl: Remove use of driver_deferred_probe_check_state_continue()
> > e2cec7d driver core: Set deferred_probe_timeout to a longer default if CONFIG_MODULES is set

Note that just setting deferred_probe_timeout = -1 like for the
CONFIG_MODULES=n case doesn't help.

> > c8c43ce driver core: Fix driver_deferred_probe_check_state() logic
> > ---
> >
> > Before these patches, on my environment [1], some device drivers
> > which has iommus property output the following message when probing:
> >
> > [ 3.222205] ravb e6800000.ethernet: ignoring dependency for device, assuming no driver
> > [ 3.257174] ravb e6800000.ethernet eth0: Base address at 0xe6800000, 2e:09:0a:02:eb:2d, IRQ 117.
> >
> > So, since ravb driver is probed within 4 seconds, we can use NFS rootfs correctly.
> >
> > However, after these patches are applied, since the patches are always waiting for 30 seconds
> > for of_iommu_configure() when IOMMU hardware is disabled, drivers/base/dd.c output WARN.
> > Also, since ravb cannot be probed for 30 seconds, we cannot use NFS rootfs anymore.
> > JFYI, I copied the kernel log to the end of this email.
>
> Hey,
> Terribly sorry for the trouble. So as Robin mentioned I have a patch
> to remove the WARN messages, but I'm a bit more concerned about why
> after the 30 second delay, the ethernet driver loads:
> [ 36.218666] ravb e6800000.ethernet eth0: Base address at
> 0xe6800000, 2e:09:0a:02:eb:2d, IRQ 117.
> but NFS fails.
>
> Is it just that the 30 second delay is too long and NFS gives up?

I added some debug code to mount_nfs_root(), which shows that the first
3 tries happen before ravb is instantiated, and the last 3 tries happen
after. So NFS root should work, if the network works.

However, it seems the Ethernet PHY is never initialized, hence the link
never becomes ready. Dmesg before/after:

ravb e6800000.ethernet eth0: Base address at 0xe6800000,
2e:09:0a:02:ea:ff, IRQ 108.

Good.

...
-gpio_rcar e6052000.gpio: sense irq = 11, type = 8

This is the GPIO the PHY IRQ is connected to.
Note that that GPIO controller has been instantiated before.

...
-Micrel KSZ9031 Gigabit PHY e6800000.ethernet-ffffffff:00:
attached PHY driver [Micrel KSZ9031 Gigabit PHY]
(mii_bus:phy_addr=e6800000.ethernet-ffffffff:00, irq=197)
...
-ravb e6800000.ethernet eth0: Link is Up - 1Gbps/Full - flow control off

Oops.

-Sending DHCP requests .., OK
-IP-Config: Got DHCP answer from ...
...
+VFS: Unable to mount root fs via NFS, trying floppy.
+VFS: Cannot open root device "nfs" or unknown-block(2,0): error -6

> Does booting with deferred_probe_timeout=0 work?

It does, as now everything using optional links (DMA and IOMMU) is now
instantiated on first try.

Gr{oetje,eeting}s,

Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds

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