linux-kernel - Re: [PATCH net-next v4 4/9] net: dsa: microchip: ksz9477: add Wake on LAN support

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Message-ID: <20231017061909.GB3539182@pengutronix.de>
Date:   Tue, 17 Oct 2023 08:19:09 +0200
From:   Oleksij Rempel <o.rempel@...gutronix.de>
To:     Florian Fainelli <f.fainelli@...il.com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Andrew Lunn <andrew@...n.ch>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Vladimir Oltean <olteanv@...il.com>,
        Woojung Huh <woojung.huh@...rochip.com>,
        Arun Ramadoss <arun.ramadoss@...rochip.com>,
        Conor Dooley <conor+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Rob Herring <robh+dt@...nel.org>, kernel@...gutronix.de,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        UNGLinuxDriver@...rochip.com,
        "Russell King (Oracle)" <linux@...linux.org.uk>,
        devicetree@...r.kernel.org
Subject: Re: [PATCH net-next v4 4/9] net: dsa: microchip: ksz9477: add Wake
 on LAN support

On Mon, Oct 16, 2023 at 08:37:50AM -0700, Florian Fainelli wrote:
> [snip]
> > +void ksz9477_get_wol(struct ksz_device *dev, int port,
> > +		     struct ethtool_wolinfo *wol)
> > +{
> > +	u8 pme_ctrl, pme_conf;
> > +	int ret;
> > +
> > +	ret = ksz_read8(dev, REG_SW_PME_CTRL, &pme_conf);
> > +	if (ret)
> > +		return;
> > +
> > +	if (!(pme_conf & PME_ENABLE))
> > +		return;
> 
> I suppose this works beause you have separate enable bits for WOL_LINKUP,
> WOL_ENERGY and WOL_MAGICPKT, you could have also left the setting of the
> PME_ENABLE bit to the set_wol() routine provided that wol->wolopts is
> non-zero.

Setting the PME_ENABLE bit in the set_wol() function might imply that it
should also be cleared within set_wol(), necessitating refcounting due
to its global bit nature.

As an alternative, the reading of the REG_SW_PME_CTRL register could be
replaced by checking the wakeup_source variable, which might result in
some optimization.

Regards,
Oleksij
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