linux-kernel - Re: [PATCH v1] of: property: Don't retry device_link

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Date:   Fri, 17 Apr 2020 13:30:05 -0700
From:   Saravana Kannan <saravanak@...gle.com>
To:     Rob Herring <robh+dt@...nel.org>
Cc:     Frank Rowand <frowand.list@...il.com>,
        Nicolas Saenz Julienne <nsaenzjulienne@...e.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Android Kernel Team <kernel-team@...roid.com>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1] of: property: Don't retry device_link_add() upon failure

On Fri, Apr 17, 2020 at 11:16 AM Rob Herring <robh+dt@...nel.org> wrote:
>
> On Thu, Apr 16, 2020 at 3:58 PM Saravana Kannan <saravanak@...gle.com> wrote:
> >
> > When of_link_to_phandle() was implemented initially, there was no way to
> > tell if device_link_add() was failing because the supplier device hasn't
> > been parsed yet, hasn't been added yet, the links were creating a cycle,
> > etc. Some of these were transient errors that'd go away at a later
> > point.
> >
> > However, with the current set of improved checks, if device_link_add()
> > fails, it'll only be for permanent errors like cycles or out-of-memory
> > errors.
>
> What improved checks? The series from Nicolas?
>

Checking for OF_POPULATED and getting the device using get_dev_from_fwnode().
OF_POPULATED ensures the node has been parsed. get_dev_from_fwnode()
ensures the device has been added to driver core.

> Is there a dependency between this and Nicolas' series?

No.

> Should this go to stable?

Kind of a grey area. I mean, if of/fw_devlink is already letting a
platform boot all the way, this doesn't fix anything. I doubt anyone
in a stable kernel is turning on this feature if it affects device
probing. I'd say the same for Nicolas' series too. It allows more
platforms to work, but if a platform is fully working, it doesn't
improve anything.

Long story short, your call for stable.

-Saravana