netdev - Re: [PATCH net] net: libwx: fix to set pause param

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Message-ID: <aAs79UDnd0sAyVAp@shell.armlinux.org.uk>
Date: Fri, 25 Apr 2025 08:38:29 +0100
From: "Russell King (Oracle)" <linux@...linux.org.uk>
To: Jiawen Wu <jiawenwu@...stnetic.com>
Cc: netdev@...r.kernel.org, pabeni@...hat.com, kuba@...nel.org,
	edumazet@...gle.com, davem@...emloft.net, andrew+netdev@...n.ch,
	mengyuanlou@...-swift.com
Subject: Re: [PATCH net] net: libwx: fix to set pause param

On Fri, Apr 25, 2025 at 03:09:42PM +0800, Jiawen Wu wrote:
> @@ -266,11 +266,20 @@ int wx_set_pauseparam(struct net_device *netdev,
>  		      struct ethtool_pauseparam *pause)
>  {
>  	struct wx *wx = netdev_priv(netdev);
> +	int err;
>  
>  	if (wx->mac.type == wx_mac_aml)
>  		return -EOPNOTSUPP;
>  
> -	return phylink_ethtool_set_pauseparam(wx->phylink, pause);
> +	err = phylink_ethtool_set_pauseparam(wx->phylink, pause);
> +	if (err)
> +		return err;
> +
> +	if (wx->fc.rx_pause != pause->rx_pause ||
> +	    wx->fc.tx_pause != pause->tx_pause)
> +		return wx_fc_enable(wx, pause->tx_pause, pause->rx_pause);

Why? phylink_ethtool_set_pauseparam() will cause mac_link_down() +
mac_link_up() to be called with the new parameters.

One of the points of phylink is to stop drivers implementing stuff
buggily - which is exactly what the above is.

->rx_pause and ->tx_pause do not set the pause enables unconditionally.
Please read the documentation in include/uapi/linux/ethtool.h which
states how these two flags are interpreted, specifically the last
paragraph of the struct's documentation.

I'm guessing your change comes from a misunderstanding how the
interface is supposed to work and you believe that phylink isn't
implementing it correctly.

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