netdev - RE: [PATCH 1/2] net: phylink: add sync flag mac_ready to fix resume issue with WoL enabled

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Date:   Wed, 30 Nov 2022 12:00:55 +0000
From:   Clark Wang <xiaoning.wang@....com>
To:     Russell King <linux@...linux.org.uk>
CC:     "peppe.cavallaro@...com" <peppe.cavallaro@...com>,
        "alexandre.torgue@...s.st.com" <alexandre.torgue@...s.st.com>,
        "joabreu@...opsys.com" <joabreu@...opsys.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "edumazet@...gle.com" <edumazet@...gle.com>,
        "kuba@...nel.org" <kuba@...nel.org>,
        "pabeni@...hat.com" <pabeni@...hat.com>,
        "mcoquelin.stm32@...il.com" <mcoquelin.stm32@...il.com>,
        "andrew@...n.ch" <andrew@...n.ch>,
        "hkallweit1@...il.com" <hkallweit1@...il.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-stm32@...md-mailman.stormreply.com" 
        <linux-stm32@...md-mailman.stormreply.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 1/2] net: phylink: add sync flag mac_ready to fix resume
 issue with WoL enabled


> -----Original Message-----
> From: Russell King <linux@...linux.org.uk>
> Sent: 2022年11月30日 19:51
> To: Clark Wang <xiaoning.wang@....com>
> Cc: peppe.cavallaro@...com; alexandre.torgue@...s.st.com;
> joabreu@...opsys.com; davem@...emloft.net; edumazet@...gle.com;
> kuba@...nel.org; pabeni@...hat.com; mcoquelin.stm32@...il.com;
> andrew@...n.ch; hkallweit1@...il.com; netdev@...r.kernel.org;
> linux-stm32@...md-mailman.stormreply.com;
> linux-arm-kernel@...ts.infradead.org; linux-kernel@...r.kernel.org
> Subject: Re: [PATCH 1/2] net: phylink: add sync flag mac_ready to fix resume
> issue with WoL enabled
> 
> On Wed, Nov 30, 2022 at 11:32:09AM +0000, Clark Wang wrote:
> > Hi Russell,
> >
> > > -----Original Message-----
> > > From: Russell King <linux@...linux.org.uk>
> > > Sent: 2022年11月30日 19:24
> > > To: Clark Wang <xiaoning.wang@....com>
> > > Cc: peppe.cavallaro@...com; alexandre.torgue@...s.st.com;
> > > joabreu@...opsys.com; davem@...emloft.net;
> edumazet@...gle.com;
> > > kuba@...nel.org; pabeni@...hat.com; mcoquelin.stm32@...il.com;
> > > andrew@...n.ch; hkallweit1@...il.com; netdev@...r.kernel.org;
> > > linux-stm32@...md-mailman.stormreply.com;
> > > linux-arm-kernel@...ts.infradead.org; linux-kernel@...r.kernel.org
> > > Subject: Re: [PATCH 1/2] net: phylink: add sync flag mac_ready to fix
> resume
> > > issue with WoL enabled
> > >
> > > On Wed, Nov 30, 2022 at 07:11:47PM +0800, Clark Wang wrote:
> > > > Issue we met:
> > > > On some platforms, mac cannot work after resumed from the suspend
> with
> > > > WoL enabled.
> > > >
> > > > The cause of the issue:
> > > > 1. phylink_resolve() is in a workqueue which will not be executed
> immediately.
> > > >    This is the call sequence:
> > > >
> phylink_resolve()->phylink_link_up()->pl->mac_ops->mac_link_up()
> > > >    For stmmac driver, mac_link_up() will set the correct
> speed/duplex...
> > > >    values which are from link_state.
> > > > 2. In stmmac_resume(), it will call stmmac_hw_setup() after called the
> > > >    phylink_resume(). stmmac_core_init() is called in function
> > > > stmmac_hw_setup(),
> > >
> > > ... and that is where the problem is. Don't call phylink_resume() before
> your
> > > hardware is ready to see a link-up event.
> >
> > Thank you very much for your reply!
> >
> > You are right.
> >
> > However, stmmac requires RXC to have a clock input when performing a
> reset(in stmmac_hw_setup()). On our board, RXC is provided by the phy.
> >
> > In WoL mode, this is not a problem, because the phy will not be down
> when suspend. RXC will keep output. But in normal suspend(without WoL),
> the phy will be down, which does not guarantee the output of the RXC of the
> phy. Therefore, the previous code will call phylink_resume() before
> stmmac_hw_setup().
> 
> I think we need phylink_phy_resume() which stmmac can use to resume the
> PHY without resuming phylink, assuming that will output the RXC. Which
> PHY driver(s) are used with stmmac?

Yes, that will be a better way! 
For now, we use AR8031 in drivers/net/phy/at803x.c and
RTL8211F/RTL8211F-VD in drivers/net/phy/realtek.c with stmmac.


Best Regards,
Clark Wang

> 
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