linux-kernel - 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 11:32:32 +0000
From:   "Russell King (Oracle)" <linux@...linux.org.uk>
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 11:23:42AM +0000, Russell King (Oracle) wrote:
> 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.

... and while that is being fixed, maybe the stupid code in
stmmac_resume() can also be fixed:

        rtnl_lock();
        if (device_may_wakeup(priv->device) && priv->plat->pmt) {
                phylink_resume(priv->phylink);
        } else {
                phylink_resume(priv->phylink);
                if (device_may_wakeup(priv->device))
                        phylink_speed_up(priv->phylink);
        }
        rtnl_unlock();

        rtnl_lock();

1. phylink_resume() is always called after that first rtnl_lock(), so
there's no point it being stupidly in each side of the if().

2. the rtnl_unlock() followed by rtnl_lock() is completely unnecessary.

Thanks.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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