From: Lukas Wunner <lukas@wunner.de>
To: Florian Fainelli <f.fainelli@gmail.com>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>,
"David S. Miller" <davem@davemloft.net>,
Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
Eric Dumazet <edumazet@google.com>,
netdev@vger.kernel.org, linux-usb@vger.kernel.org,
Steve Glendinning <steve.glendinning@shawell.net>,
UNGLinuxDriver@microchip.com, Oliver Neukum <oneukum@suse.com>,
Andre Edich <andre.edich@microchip.com>,
Oleksij Rempel <linux@rempel-privat.de>,
Martyn Welch <martyn.welch@collabora.com>,
Gabriel Hojda <ghojda@yo2urs.ro>,
Christoph Fritz <chf.fritz@googlemail.com>,
Lino Sanfilippo <LinoSanfilippo@gmx.de>,
Philipp Rosenberger <p.rosenberger@kunbus.com>,
Heiner Kallweit <hkallweit1@gmail.com>,
Andrew Lunn <andrew@lunn.ch>,
Russell King <linux@armlinux.org.uk>,
Ferry Toth <fntoth@gmail.com>,
Krzysztof Kozlowski <krzk@kernel.org>,
'Linux Samsung SOC' <linux-samsung-soc@vger.kernel.org>
Subject: Re: [PATCH net-next v3 5/7] usbnet: smsc95xx: Forward PHY interrupts to PHY driver to avoid polling
Date: Fri, 23 Sep 2022 06:20:37 +0200 [thread overview]
Message-ID: <20220923042037.GA10101@wunner.de> (raw)
In-Reply-To: <adb2de4e-0ad0-a94a-93e6-572f58a2141b@gmail.com>
On Sun, Sep 18, 2022 at 03:11:47PM -0700, Florian Fainelli wrote:
> On 9/18/2022 1:55 PM, Lukas Wunner wrote:
> > On Sun, Sep 18, 2022 at 01:41:13PM -0700, Florian Fainelli wrote:
> > > On 9/18/2022 12:13 PM, Lukas Wunner wrote:
> > > > On Mon, Aug 29, 2022 at 01:40:05PM +0200, Marek Szyprowski wrote:
> > > > > I've finally traced what has happened. I've double checked and indeed
> > > > > the 1758bde2e4aa commit fixed the issue on next-20220516 kernel and as
> > > > > such it has been merged to linus tree. Then the commit 744d23c71af3
> > > > > ("net: phy: Warn about incorrect mdio_bus_phy_resume() state") has been
> > > > > merged to linus tree, which triggers a new warning during the
> > > > > suspend/resume cycle with smsc95xx driver. Please note, that the
> > > > > smsc95xx still works fine regardless that warning. However it look that
> > > > > the commit 1758bde2e4aa only hide a real problem, which the commit
> > > > > 744d23c71af3 warns about.
> > > > >
> > > > > Probably a proper fix for smsc95xx driver is to call phy_stop/start
> > > > > during suspend/resume cycle, like in similar patches for other drivers:
> > > > >
> > > > > https://lore.kernel.org/all/20220825023951.3220-1-f.fainelli@gmail.com/
> > > >
> > > > No, smsc95xx.c relies on mdio_bus_phy_{suspend,resume}() and there's
> > > > no need to call phy_{stop,start}() >
> > > > 744d23c71af3 was flawed and 6dbe852c379f has already fixed a portion
> > > > of the fallout.
> > > >
> > > > However the WARN() condition still seems too broad and causes false
> > > > positives such as in your case. In particular, mdio_bus_phy_suspend()
> > > > may leave the device in PHY_UP state, so that's a legal state that
> > > > needs to be exempted from the WARN().
> > >
> > > How is that a legal state when the PHY should be suspended? Even if we are
> > > interrupt driven, the state machine should be stopped, does not mean that
> > > Wake-on-LAN or other activity interrupts should be disabled.
> >
> > mdio_bus_phy_suspend()
> > phy_stop_machine()
> > phydev->state = PHY_UP # if (phydev->state >= PHY_UP)
> >
> > So apparently PHY_UP is a legal state for a suspended PHY.
>
> It is not clear to me why, however. Sure it does ensure that when we resume
> we set needs_aneg = true but this feels like a hack in the sense that we are
> setting the PHY in a provisional state in anticipation for what might come
> next.
I've just submitted a fix so that at least v6.0 doesn't get released
with a false-positive WARN splat on resume:
https://lore.kernel.org/netdev/8128fdb51eeebc9efbf3776a4097363a1317aaf1.1663905575.git.lukas@wunner.de/
I guess we can look into making the state setting more logical in a
separate step.
> > > If you allow PHY_UP, then the warning becomes effectively useless, so I
> > > don't believe this is quite what you want to do here.
> >
> > Hm, maybe the WARN() should be dropped altogether?
>
> And then be left with debugging similar problems that prompted me to submit
> the patch in the first place, no thank you. I guess I would rather accept
> that PHY_UP needs to be special cased then.
I've interpreted that as an Acked-by for exempting PHY_UP.
If that was not what you wanted, please speak up.
Thanks,
Lukas
next prev parent reply other threads:[~2022-09-23 4:20 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-05-12 8:42 [PATCH net-next v3 0/7] Polling be gone on LAN95xx Lukas Wunner
2022-05-12 8:42 ` [PATCH net-next v3 1/7] usbnet: Run unregister_netdev() before unbind() again Lukas Wunner
2022-05-12 8:42 ` [PATCH net-next v3 2/7] usbnet: smsc95xx: Don't clear read-only PHY interrupt Lukas Wunner
2022-05-12 11:57 ` Lukas Wunner
2022-05-12 8:42 ` [PATCH net-next v3 3/7] usbnet: smsc95xx: Don't reset PHY behind PHY driver's back Lukas Wunner
2022-05-12 12:12 ` Lukas Wunner
2022-05-12 8:42 ` [PATCH net-next v3 4/7] usbnet: smsc95xx: Avoid link settings race on interrupt reception Lukas Wunner
2022-05-12 12:15 ` Lukas Wunner
2022-05-12 8:42 ` [PATCH net-next v3 5/7] usbnet: smsc95xx: Forward PHY interrupts to PHY driver to avoid polling Lukas Wunner
[not found] ` <CGME20220517101846eucas1p2c132f7e7032ed00996e222e9cc6cdf99@eucas1p2.samsung.com>
2022-05-17 10:18 ` Marek Szyprowski
2022-05-19 19:08 ` Lukas Wunner
2022-05-19 21:22 ` Marek Szyprowski
2022-05-23 9:43 ` Lukas Wunner
2022-05-23 11:38 ` Marek Szyprowski
2022-05-23 12:34 ` Andrew Lunn
2022-05-23 13:47 ` Lukas Wunner
2022-05-24 0:52 ` Andrew Lunn
2022-05-24 1:08 ` Andrew Lunn
2022-05-24 6:16 ` Marek Szyprowski
2022-05-24 12:03 ` Andrew Lunn
2022-05-26 13:55 ` Lukas Wunner
2022-05-24 12:13 ` Lukas Wunner
2022-06-06 1:28 ` Andrew Lunn
2022-08-26 6:51 ` Marek Szyprowski
2022-08-26 7:19 ` Lukas Wunner
2022-08-26 7:41 ` Marek Szyprowski
2022-08-26 7:53 ` Lukas Wunner
2022-08-26 8:29 ` Marek Szyprowski
2022-08-29 11:40 ` Marek Szyprowski
2022-09-18 19:13 ` Lukas Wunner
2022-09-18 20:41 ` Florian Fainelli
2022-09-18 20:55 ` Lukas Wunner
2022-09-18 22:11 ` Florian Fainelli
2022-09-23 4:20 ` Lukas Wunner [this message]
2022-09-22 13:21 ` Marek Szyprowski
2022-05-12 8:42 ` [PATCH net-next v3 6/7] net: phy: smsc: Cache interrupt mask Lukas Wunner
2022-05-12 12:17 ` Lukas Wunner
2022-05-12 8:42 ` [PATCH net-next v3 7/7] net: phy: smsc: Cope with hot-removal in interrupt handler Lukas Wunner
2022-05-12 12:19 ` Lukas Wunner
2022-05-13 10:40 ` [PATCH net-next v3 0/7] Polling be gone on LAN95xx patchwork-bot+netdevbpf
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