linux-kernel - Re: How to fix WARN from drivers/base/dd.c in next-20200401 if CONFIG

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Date:   Thu, 2 Apr 2020 10:25:05 -0700
From:   John Stultz <john.stultz@...aro.org>
To:     Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>
Cc:     "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "rafael@...nel.org" <rafael@...nel.org>,
        "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: How to fix WARN from drivers/base/dd.c in next-20200401 if CONFIG_MODULES=y?

On Thu, Apr 2, 2020 at 3:17 AM Yoshihiro Shimoda
<yoshihiro.shimoda.uh@...esas.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
> 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?

Does booting with deferred_probe_timeout=0 work?

thanks
-john