linux-kernel - Re: [PATCH v1 0/5] Enable fw

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Date:   Mon, 21 Dec 2020 10:48:23 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Saravana Kannan <saravanak@...gle.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        "Cc: Android Kernel" <kernel-team@...roid.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Jisheng Zhang <Jisheng.Zhang@...aptics.com>,
        Kevin Hilman <khilman@...libre.com>,
        John Stultz <john.stultz@...aro.org>,
        Nicolas Saenz Julienne <nsaenzjulienne@...e.de>,
        Marc Zyngier <maz@...nel.org>
Subject: Re: [PATCH v1 0/5] Enable fw_devlink=on by default

On Fri, Dec 18, 2020 at 4:17 AM Saravana Kannan <saravanak@...gle.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?

Honestly, I'd rather not (but it's up to Greg).

This is a new series posted during the merge window, so it should not
be looked at even according to the rules.

Personally, I don't have the time to look at it now.

> 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.

So it should be posted right after -rc1 and spend a whole cycle in linux-next.

> If we do end up have to revert anything, it'll just be Patch 5/5 (a one
> liner).

Which totally doesn't matter IMV.