RE: [PATCH] net: stmmac: fix MAC not working when system resume back with WoL enabled

[Joakim Zhang <qiangqing.zhang@nxp.com>]

Hi Heiner,

> -----Original Message-----
> From: Heiner Kallweit <hkallweit1@gmail.com>
> Sent: 2021年9月1日 23:40
> To: Joakim Zhang <qiangqing.zhang@nxp.com>; Russell King
> <linux@armlinux.org.uk>
> Cc: peppe.cavallaro@st.com; alexandre.torgue@foss.st.com;
> joabreu@synopsys.com; davem@davemloft.net; kuba@kernel.org;
> mcoquelin.stm32@gmail.com; netdev@vger.kernel.org; andrew@lunn.ch;
> f.fainelli@gmail.com; dl-linux-imx <linux-imx@nxp.com>
> Subject: Re: [PATCH] net: stmmac: fix MAC not working when system resume
> back with WoL enabled
> 
> On 01.09.2021 12:21, Joakim Zhang wrote:
> >
> > Hi Russell,
> >
> >> -----Original Message-----
> >> From: Russell King <linux@armlinux.org.uk>
> >> Sent: 2021年9月1日 17:14
> >> To: Joakim Zhang <qiangqing.zhang@nxp.com>
> >> Cc: peppe.cavallaro@st.com; alexandre.torgue@foss.st.com;
> >> joabreu@synopsys.com; davem@davemloft.net; kuba@kernel.org;
> >> mcoquelin.stm32@gmail.com; netdev@vger.kernel.org; andrew@lunn.ch;
> >> f.fainelli@gmail.com; hkallweit1@gmail.com; dl-linux-imx
> >> <linux-imx@nxp.com>
> >> Subject: Re: [PATCH] net: stmmac: fix MAC not working when system
> >> resume back with WoL enabled
> >>
> >> On Wed, Sep 01, 2021 at 05:02:28PM +0800, Joakim Zhang wrote:
> >>> We can reproduce this issue with below steps:
> >>> 1) enable WoL on the host
> >>> 2) host system suspended
> >>> 3) remote client send out wakeup packets We can see that host system
> >>> resume back, but can't work, such as ping failed.
> >>>
> >>> After a bit digging, this issue is introduced by the commit
> >>> 46f69ded988d
> >>> ("net: stmmac: Use resolved link config in mac_link_up()"), which
> >>> use the finalised link parameters in mac_link_up() rather than the
> >>> parameters in mac_config().
> >>>
> >>> There are two scenarios for MAC suspend/resume:
> >>>
> >>> 1) MAC suspend with WoL disabled, stmmac_suspend() call
> >>> phylink_mac_change() to notify phylink machine that a change in MAC
> >>> state, then .mac_link_down callback would be invoked. Further, it
> >>> will call phylink_stop() to stop the phylink instance. When MAC
> >>> resume back, firstly phylink_start() is called to start the phylink
> >>> instance, then call phylink_mac_change() which will finally trigger
> >>> phylink machine to invoke .mac_config and .mac_link_up callback. All
> >>> is fine since configuration in these two callbacks will be initialized.
> >>>
> >>> 2) MAC suspend with WoL enabled, phylink_mac_change() will put link
> >>> down, but there is no phylink_stop() to stop the phylink instance,
> >>> so it will link up again, that means .mac_config and .mac_link_up
> >>> would be invoked before system suspended. After system resume back,
> >>> it will do DMA initialization and SW reset which let MAC lost the
> >>> hardware setting (i.e MAC_Configuration register(offset 0x0) is
> >>> reset). Since link is up before system suspended, so .mac_link_up
> >>> would not be invoked after system resume back, lead to there is no
> >>> chance to initialize the configuration in .mac_link_up callback, as
> >>> a result, MAC can't work any longer.
> >>>
> >>> Above description is what I found when debug this issue, this patch
> >>> is just revert broken patch to workaround it, at least make MAC work
> >>> when system resume back with WoL enabled.
> >>>
> >>> Said this is a workaround, since it has not resolve the issue completely.
> >>> I just move the speed/duplex/pause etc into .mac_config callback,
> >>> there are other configurations in .mac_link_up callback which also
> >>> need to be initialized to work for specific functions.
> >>
> >> NAK. Please read the phylink documentation. speed/duplex/pause is
> >> undefined in .mac_config.
> >
> > Speed/duplex/pause also the field of " struct phylink_link_state", so
> > these can be refered in .mac_config, please see the link which stmmac did
> before:
> > https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Felix
> >
> ir.bootlin.com%2Flinux%2Fv5.4.143%2Fsource%2Fdrivers%2Fnet%2Fethernet%
> >
> 2Fstmicro%2Fstmmac%2Fstmmac_main.c%23L852&amp;data=04%7C01%7Cq
> iangqing
> > .zhang%40nxp.com%7C83fda179bf1d41fca42008d96d5ed3c3%7C686ea1d3b
> c2b4c6f
> >
> a92cd99c5c301635%7C0%7C0%7C637661076316192906%7CUnknown%7CTW
> FpbGZsb3d8
> >
> eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D
> %7C1
> >
> 000&amp;sdata=zM%2Fw1R%2BHkY067pg8wm2%2FS0zsLoBNQQ2TmdXWJat
> Ptes%3D&amp
> > ;reserved=0
> >
> >
> >> I think the problem here is that you're not calling phylink_stop()
> >> when WoL is enabled, which means phylink will continue to maintain
> >> the state as per the hardware state, and phylib will continue to run
> >> its state machine reporting the link state to phylink.
> >
> > Yes, I also tried do below code change, but the host would not be
> > wakeup, phylink_stop() would call phy_stop(), phylib would call
> > phy_suspend() finally, it will not suspend phy if it detect WoL enabled, so now
> I don't know why system can't be wakeup with this code change.
> >
> Follow-up question would be whether link breaks accidentally on suspend, or
> whether something fails on resume.When suspending, does the link break and
> link LEDs go off?

No, the LEDs is normal.

> Depending on LED configuration you may also see whether link speed is
> reduced on suspend.
> struct net_device has a member wol_enabled, does it make a difference if set
> it?

I have a try, there is no help. Have not clear why phylink_stop() will break WoL function,
lead it can't be waked up via magic packets.

Thanks.

Best Regards,
Joakim Zhang