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Date:   Mon, 13 Sep 2021 09:51:00 -0700
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Subject: Re: [RFC PATCH net 4/5] net: dsa: microchip: ksz8863: be compatible
 with masters which unregister on shutdown
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To:     Vladimir Oltean <vladimir.oltean@nxp.com>, netdev@vger.kernel.org
Cc:     Andrew Lunn <andrew@lunn.ch>,
        Vivien Didelot <vivien.didelot@gmail.com>,
        Vladimir Oltean <olteanv@gmail.com>,
        "David S. Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>,
        Kurt Kanzenbach <kurt@linutronix.de>,
        Hauke Mehrtens <hauke@hauke-m.de>,
        Woojung Huh <woojung.huh@microchip.com>,
        UNGLinuxDriver@microchip.com, Sean Wang <sean.wang@mediatek.com>,
        Landen Chao <Landen.Chao@mediatek.com>,
        DENG Qingfang <dqfext@gmail.com>,
        Matthias Brugger <matthias.bgg@gmail.com>,
        Claudiu Manoil <claudiu.manoil@nxp.com>,
        Alexandre Belloni <alexandre.belloni@bootlin.com>,
        Linus Walleij <linus.walleij@linaro.org>,
        George McCollister <george.mccollister@gmail.com>,
        Heiner Kallweit <hkallweit1@gmail.com>,
        Russell King <linux@armlinux.org.uk>,
        Oleksij Rempel <linux@rempel-privat.de>,
        Michael Grzeschik <m.grzeschik@pengutronix.de>,
        linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linux-mediatek@lists.infradead.org,
        Lino Sanfilippo <LinoSanfilippo@gmx.de>
References: <20210912120932.993440-1-vladimir.oltean@nxp.com>
 <20210912120932.993440-5-vladimir.oltean@nxp.com>
From:   Florian Fainelli <f.fainelli@gmail.com>
In-Reply-To: <20210912120932.993440-5-vladimir.oltean@nxp.com>
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On 9/12/2021 5:09 AM, Vladimir Oltean wrote:
> Since commit 2f1e8ea726e9 ("net: dsa: link interfaces with the DSA
> master to get rid of lockdep warnings"), DSA gained a requirement which
> it did not fulfill, which is to unlink itself from the DSA master at
> shutdown time.
> 
> Since the Microchip sub-driver for KSZ8863 was introduced after the bad
> commit, it has never worked with DSA masters which decide to unregister
> their net_device on shutdown, effectively hanging the reboot process.
> To fix that, we need to call dsa_switch_shutdown.
> 
> Since this driver expects the MDIO bus to be backed by mdio_bitbang, I
> don't think there is currently any MDIO bus driver which implements its
> ->shutdown by redirecting it to ->remove, but in any case, to be
> compatible with that pattern, it is necessary to implement an "if this
> then not that" scheme, to avoid ->remove and ->shutdown from being
> called both for the same struct device.
> 
> Fixes: 60a364760002 ("net: dsa: microchip: Add Microchip KSZ8863 SMI based driver support")
> Link: https://lore.kernel.org/netdev/20210909095324.12978-1-LinoSanfilippo@gmx.de/
> Reported-by: Lino Sanfilippo <LinoSanfilippo@gmx.de>
> Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>

Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
-- 
Florian