Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Thu, 19 May 2022 17:32:35 +0200
From:   Andrew Lunn <andrew@lunn.ch>
To:     Vladimir Oltean <vladimir.oltean@nxp.com>
Cc:     "netdev@vger.kernel.org" <netdev@vger.kernel.org>,
        Jakub Kicinski <kuba@kernel.org>,
        "David S. Miller" <davem@davemloft.net>,
        Paolo Abeni <pabeni@redhat.com>,
        Eric Dumazet <edumazet@google.com>,
        Florian Fainelli <f.fainelli@gmail.com>,
        Vivien Didelot <vivien.didelot@gmail.com>,
        Vladimir Oltean <olteanv@gmail.com>,
        "devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Saravana Kannan <saravanak@google.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        "Rafael J. Wysocki" <rafael@kernel.org>,
        Robin Murphy <robin.murphy@arm.com>,
        Geert Uytterhoeven <geert+renesas@glider.be>,
        Rob Herring <robh+dt@kernel.org>,
        Frank Rowand <frowand.list@gmail.com>,
        John Stultz <jstultz@google.com>,
        Alvin =?utf-8?B?4pS8w6FpcHJhZ2E=?= <alsi@bang-olufsen.dk>,
        Russell King <rmk+kernel@armlinux.org.uk>,
        Heiner Kallweit <hkallweit1@gmail.com>
Subject: Re: [RFC PATCH net 0/2] Make phylink and DSA wait for PHY driver
 that defers probe
Message-ID: <YoZjE77QvIGifDnY@lunn.ch>
References: <20220513233640.2518337-1-vladimir.oltean@nxp.com>
 <Yn72l3O6yI7YstMf@lunn.ch>
 <20220519145936.3ofmmnrehydba7t6@skbuf>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20220519145936.3ofmmnrehydba7t6@skbuf>
Precedence: bulk

> > There is a very different approach, which might be simpler.
> > 
> > We know polling will always work. And it should be possible to
> > transition between polling and interrupt at any point, so long as the
> > phylock is held. So if you get -EPROBE_DEFFER during probe, mark some
> > state in phydev that there should be an irq, but it is not around yet.
> > When the phy is started, and phylib starts polling, look for the state
> > and try getting the IRQ again. If successful, swap to interrupts, if
> > not, keep polling. Maybe after 60 seconds of polling and trying, give
> > up trying to find the irq and stick with polling.
> 
> That doesn't sound like something that I'd backport to stable kernels.

> What motivates me to make these changes in the first place is the idea
> that current kernels should work with updated device trees.

By current, you mean old kernels, LTS etc. You want an LTS kernel to
work with a new DT blob? You want forward compatibility with a DT
blob. Do the stable rules say anything about that?

      Andrew