netdev - Re: [PATCH net-next 1/1] net: phy: marvell10g: Add WAKE

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Date:   Mon, 16 Aug 2021 09:18:12 +0100
From:   "Russell King (Oracle)" <linux@...linux.org.uk>
To:     "Song, Yoong Siang" <yoong.siang.song@...el.com>
Cc:     Andrew Lunn <andrew@...n.ch>,
        Marek Behún <kabel@...nel.org>,
        Heiner Kallweit <hkallweit1@...il.com>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net-next 1/1] net: phy: marvell10g: Add WAKE_PHY support
 to WOL event

On Mon, Aug 16, 2021 at 08:03:59AM +0000, Song, Yoong Siang wrote:
> Thanks for your explanation. I understand your concern better now.
> 
> In the case of WoL hasn't been enabled through a set_wol call, the PHY will
> be suspended, so we no need worry the link change interrupt will create
> an undesired WoL event. 
> 
> In the case of set_wol is called to disable WAKE_PHY event, we can keep
> the link change interrupt enable, so that it won't affect the interrupt
> support.

I think you're missing the point. In your get_wol method for this
PHY:

+       ret = phy_read_mmd(phydev, MDIO_MMD_PCS, MV_PCS_INTR_ENABLE);
+       if (ret < 0)
+               return;
+
+       if (ret & MV_PCS_INTR_ENABLE_LSC)
+               wol->wolopts |= WAKE_PHY;

If the link change interrupt is enabled because we want to use
interrupt support, the above code has the effect of reporting to
userspace that WoL is enabled, even when nothing has requested WoL
to be enabled.

This also has the effect of preventing the PHY being suspended (see
phy_suspend()) and in effect means that WoL is enabled, even though
set_wol() was not called.

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