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Subject: Re: How to fix WARN from drivers/base/dd.c in next-20200401 if
 CONFIG_MODULES=y?
To:     Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>,
        "john.stultz@linaro.org" <john.stultz@linaro.org>
Cc:     "gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>,
        "iommu@lists.linux-foundation.org" <iommu@lists.linux-foundation.org>,
        LKML <linux-kernel@vger.kernel.org>,
        "rafael@kernel.org" <rafael@kernel.org>
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From:   Robin Murphy <robin.murphy@arm.com>
Message-ID: <b0dea497-b272-e74a-ac9c-3a3cd653a9f9@arm.com>
Date:   Thu, 2 Apr 2020 14:20:03 +0100
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On 2020-04-02 11:16 am, Yoshihiro Shimoda wrote:
> Hi John,
> 
> 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.
> 
> I guess the patches will be merged into v5.7-rc1 because the patches are contained from
> next-20200316, I'd like to fix the issue in v5.7-rcN cycle somehow.

This already came up in a different context, and there's a proposal from 
John here:

https://lore.kernel.org/lkml/20200330202715.86609-1-john.stultz@linaro.org/

Robin.