netdev - Re: [PATCH 0/3] Fix for KSZ DSA switch shutdown

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Message-ID: <20210913104400.oyib42rfq5x2vc56@skbuf>
Date:   Mon, 13 Sep 2021 13:44:00 +0300
From:   Vladimir Oltean <olteanv@...il.com>
To:     Lino Sanfilippo <LinoSanfilippo@....de>
Cc:     Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>,
        Saravana Kannan <saravanak@...gle.com>,
        "Rafael J. Wysocki" <rafael@...nel.org>, p.rosenberger@...bus.com,
        woojung.huh@...rochip.com, UNGLinuxDriver@...rochip.com,
        vivien.didelot@...il.com, davem@...emloft.net, kuba@...nel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/3] Fix for KSZ DSA switch shutdown

On Mon, Sep 13, 2021 at 12:32:14PM +0200, Lino Sanfilippo wrote:
> Hi,
> 
> > Gesendet: Sonntag, 12. September 2021 um 22:29 Uhr
> > Von: "Vladimir Oltean" <olteanv@...il.com>
> > An: "Lino Sanfilippo" <LinoSanfilippo@....de>
> > Cc: "Andrew Lunn" <andrew@...n.ch>, "Florian Fainelli" <f.fainelli@...il.com>, "Saravana Kannan" <saravanak@...gle.com>, "Rafael J. Wysocki" <rafael@...nel.org>, p.rosenberger@...bus.com, woojung.huh@...rochip.com, UNGLinuxDriver@...rochip.com, vivien.didelot@...il.com, davem@...emloft.net, kuba@...nel.org, netdev@...r.kernel.org, linux-kernel@...r.kernel.org
> > Betreff: Re: [PATCH 0/3] Fix for KSZ DSA switch shutdown
> >
> > On Sun, Sep 12, 2021 at 10:19:24PM +0200, Lino Sanfilippo wrote:
> > >
> > > Hi,
> > >
> > > On 10.09.21 at 16:58, Vladimir Oltean wrote:
> > > > On Fri, Sep 10, 2021 at 01:51:56PM +0200, Andrew Lunn wrote:
> > > >>> It does not really scale but we also don't have that many DSA masters to
> > > >>> support, I believe I can name them all: bcmgenet, stmmac, bcmsysport, enetc,
> > > >>> mv643xx_eth, cpsw, macb.
> > > >>
> > > >> fec, mvneta, mvpp2, i210/igb.
> > > >
> > > > I can probably double that list only with Freescale/NXP Ethernet
> > > > drivers, some of which are not even submitted to mainline. To name some
> > > > mainline drivers: gianfar, dpaa-eth, dpaa2-eth, dpaa2-switch, ucc_geth.
> > > > Also consider that DSA/switchdev drivers can also be DSA masters of
> > > > their own, we have boards doing that too.
> > > >
> > > > Anyway, I've decided to at least try and accept the fact that DSA
> > > > masters will unregister their net_device on shutdown, and attempt to do
> > > > something sane for all DSA switches in that case.
> > > >
> > > > Attached are two patches (they are fairly big so I won't paste them
> > > > inline, and I would like initial feedback before posting them to the
> > > > list).
> > > >
> > > > As mentioned in those patches, the shutdown ordering guarantee is still
> > > > very important, I still have no clue what goes on there, what we need to
> > > > do, etc.
> > > >
> > >
> > > I tested these patches with my 5.10 kernel (based on Gregs 5.10.27 stable
> > > kernel) and while I do not see the message "unregister_netdevice: waiting
> > > for eth0 to become free. Usage count = 2." any more the shutdown/reboot hangs, too.
> > > After a few attempts without any error messages on the console I was able to get a
> > >  stack trace. Something still seems to go wrong in bcm2835_spi_shutdown() (see attachment).
> > > I have not had the time yet to investigate this further (or to test the patches
> > >  with a newer kernel).
> >
> > Could you post the full kernel output? The picture you've posted is
> > truncated and only shows a WARN_ON in rpi_firmware_transaction and is
> > probably a symptom and not the issue (which is above and not shown).
> >
> 
> Unfortunately I dont see anything in the kernel log. The console output is all I get,
> thats why I made the photo.

To clarify, are you saying nothing above this line gets printed? Because
the part of the log you've posted in the picture is pretty much
unworkable:

[   99.375389] [<bf0dc56c>] (bcm2835_spi_shutdown [spi_bcm2835]) from [<c0863ca0>] (platform_drv_shutdown+0x2c/0x30)

How do you access the device's serial console? Use a program with a
scrollback buffer like GNU screen or something.