Re: [PATCH net-next v3 5/7] usbnet: smsc95xx: Forward PHY interrupts to PHY driver to avoid polling

From: Marek Szyprowski <m.szyprowski@samsung.com>
To: Lukas Wunner <lukas@wunner.de>
Cc: "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>,
	Florian Fainelli <f.fainelli@gmail.com>
Subject: Re: [PATCH net-next v3 5/7] usbnet: smsc95xx: Forward PHY interrupts to PHY driver to avoid polling
Date: Thu, 22 Sep 2022 15:21:52 +0200	[thread overview]
Message-ID: <373b0f34-8154-e4a3-208e-3b52e59cb932@samsung.com> (raw)
In-Reply-To: <20220918191333.GA2107@wunner.de>

On 18.09.2022 21:13, Lukas Wunner wrote:
> [cc += Florian]
>
> 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().
>
> Does the issue still appear even after 6dbe852c379f?
>
> If it does, could you test whether exempting PHY_UP silences the
> gratuitous WARN splat?  I.e.:
>
> -	WARN_ON(phydev->state != PHY_HALTED && phydev->state != PHY_READY);
> +	WARN_ON(phydev->state != PHY_HALTED && phydev->state != PHY_READY &&
> +		phydev->state != PHY_UP);

Yes, this hides this warning in my case. I've tested on linux 
next-20220921 with the above change.

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland