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From:   Saravana Kannan <saravanak@google.com>
Date:   Fri, 18 Dec 2020 13:11:13 -0800
Message-ID: <CAGETcx9K8f8c+AT_AVtbgDn3=N9YtytoThj-KX_JQO9KfvTr1Q@mail.gmail.com>
Subject: Re: [PATCH v1 0/5] Enable fw_devlink=on by default
To:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        "Rafael J. Wysocki" <rafael@kernel.org>
Cc:     Android Kernel Team <kernel-team@android.com>,
        LKML <linux-kernel@vger.kernel.org>,
        Jisheng Zhang <Jisheng.Zhang@synaptics.com>,
        Kevin Hilman <khilman@baylibre.com>,
        John Stultz <john.stultz@linaro.org>,
        Nicolas Saenz Julienne <nsaenzjulienne@suse.de>,
        Marc Zyngier <maz@kernel.org>
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On Thu, Dec 17, 2020 at 7:17 PM Saravana Kannan <saravanak@google.com> wrote:
>
> As discussed in LPC 2020, cyclic dependencies in firmware that couldn't
> be broken using logic was one of the last remaining reasons
> fw_devlink=on couldn't be set by default.
>
> This series changes fw_devlink so that when a cyclic dependency is found
> in firmware, the links between those devices fallback to permissive mode
> behavior. This way, the rest of the system still benefits from
> fw_devlink, but the ambiguous cases fallback to permissive mode.
>
> Setting fw_devlink=on by default brings a bunch of benefits (currently,
> only for systems with device tree firmware):
> * Significantly cuts down deferred probes.
> * Device probe is effectively attempted in graph order.
> * Makes it much easier to load drivers as modules without having to
>   worry about functional dependencies between modules (depmod is still
>   needed for symbol dependencies).
>
> Greg/Rafael,
>
> Can we get this pulled into 5.11-rc1 or -rc2 soon please? I expect to
> see some issues due to device drivers that aren't following best
> practices (they don't expose the device to driver core). Want to
> identify those early on and try to have them fixed before 5.11 release.
> See [1] for an example of such a case.
>
> If we do end up have to revert anything, it'll just be Patch 5/5 (a one
> liner).
>
> Marc,
>
> You had hit issues with fw_devlink=on before on some of your systems.
> Want to give this a shot?

Marc,

If you decide to test this, please also pull in this patch. It should
fix all your interrupt issues.

https://lore.kernel.org/lkml/20201218210750.3455872-1-saravanak@google.com/

-Saravana