netdev - Re: [PATCH net-next v2 6/6] net: dsa: b53: remove eee_enabled/eee_active in b53_get_mac

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Message-ID: <20240206112024.3jxtcru3dupeirnj@skbuf>
Date: Tue, 6 Feb 2024 13:20:24 +0200
From: Vladimir Oltean <olteanv@...il.com>
To: "Russell King (Oracle)" <rmk+kernel@...linux.org.uk>,
	Florian Fainelli <florian.fainelli@...adcom.com>,
	Doug Berger <opendmb@...il.com>
Cc: Andrew Lunn <andrew@...n.ch>, Heiner Kallweit <hkallweit1@...il.com>,
	Alexandre Torgue <alexandre.torgue@...s.st.com>,
	bcm-kernel-feedback-list@...adcom.com,
	Byungho An <bh74.an@...sung.com>,
	Clark Wang <xiaoning.wang@....com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Jose Abreu <joabreu@...opsys.com>,
	Justin Chen <justin.chen@...adcom.com>,
	linux-arm-kernel@...ts.infradead.org,
	linux-stm32@...md-mailman.stormreply.com,
	Maxime Coquelin <mcoquelin.stm32@...il.com>, netdev@...r.kernel.org,
	NXP Linux Team <linux-imx@....com>, Paolo Abeni <pabeni@...hat.com>,
	Shenwei Wang <shenwei.wang@....com>, Wei Fang <wei.fang@....com>
Subject: Re: [PATCH net-next v2 6/6] net: dsa: b53: remove
 eee_enabled/eee_active in b53_get_mac_eee()

On Sun, Feb 04, 2024 at 12:13:28PM +0000, Russell King (Oracle) wrote:
> b53_get_mac_eee() sets both eee_enabled and eee_active, and then
> returns zero.
> 
> dsa_slave_get_eee(), which calls this function, will then continue to
> call phylink_ethtool_get_eee(), which will return -EOPNOTSUPP if there
> is no PHY present, otherwise calling phy_ethtool_get_eee() which in
> turn will call genphy_c45_ethtool_get_eee().

Nitpick: If you need to resend, the function name changed to
dsa_user_get_eee().

> 
> genphy_c45_ethtool_get_eee() will overwrite eee_enabled and eee_active
> with its own interpretation from the PHYs settings and negotiation
> result.
> 
> Thus, when there is no PHY, dsa_slave_get_eee() will fail with

Here too.

> -EOPNOTSUPP, meaning eee_enabled and eee_active will not be returned to
> userspace. When there is a PHY, eee_enabled and eee_active will be
> overwritten by phylib, making the setting of these members in
> b53_get_mac_eee() entirely unnecessary.
> 
> Remove this code, thus simplifying b53_get_mac_eee().
> 
> Reviewed-by: Andrew Lunn <andrew@...n.ch>
> Reviewed-by: Florian Fainelli <florian.fainelli@...adcom.com>
> Signed-off-by: Russell King (Oracle) <rmk+kernel@...linux.org.uk>
> ---
>  drivers/net/dsa/b53/b53_common.c | 6 ------
>  1 file changed, 6 deletions(-)
> 
> diff --git a/drivers/net/dsa/b53/b53_common.c b/drivers/net/dsa/b53/b53_common.c
> index adc93abf4551..9e4c9bd6abcc 100644
> --- a/drivers/net/dsa/b53/b53_common.c
> +++ b/drivers/net/dsa/b53/b53_common.c
> @@ -2227,16 +2227,10 @@ EXPORT_SYMBOL(b53_eee_init);
>  int b53_get_mac_eee(struct dsa_switch *ds, int port, struct ethtool_keee *e)
>  {
>  	struct b53_device *dev = ds->priv;
> -	struct ethtool_keee *p = &dev->ports[port].eee;
> -	u16 reg;
>  
>  	if (is5325(dev) || is5365(dev))
>  		return -EOPNOTSUPP;
>  
> -	b53_read16(dev, B53_EEE_PAGE, B53_EEE_LPI_INDICATE, &reg);
> -	e->eee_enabled = p->eee_enabled;
> -	e->eee_active = !!(reg & BIT(port));
> -

I know next to nothing about EEE and especially the implementation on
Broadcom switches. But is the information brought by B53_EEE_LPI_INDICATE
completely redundant? Is it actually in the system's best interest to
ignore it?

>  	return 0;
>  }
>  EXPORT_SYMBOL(b53_get_mac_eee);
> -- 
> 2.30.2
>