linux-kernel - Re: [PATCH net-next v3 1/3] net: dsa: rzn1-a5psw: use a5psw_reg

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Date:   Wed, 8 Feb 2023 23:37:57 +0200
From:   Vladimir Oltean <olteanv@...il.com>
To:     Clément Léger <clement.leger@...tlin.com>
Cc:     Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        Herve Codina <herve.codina@...tlin.com>,
        Miquèl Raynal <miquel.raynal@...tlin.com>,
        Milan Stevanovic <milan.stevanovic@...com>,
        Jimmy Lalande <jimmy.lalande@...com>,
        Pascal Eberhard <pascal.eberhard@...com>,
        Arun Ramadoss <Arun.Ramadoss@...rochip.com>,
        linux-renesas-soc@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next v3 1/3] net: dsa: rzn1-a5psw: use
 a5psw_reg_rmw() to modify flooding resolution

On Wed, Feb 08, 2023 at 05:17:47PM +0100, Clément Léger wrote:
> .port_bridge_flags will be added and allows to modify the flood mask
> independently for each port. Keeping the existing bridged_ports write
> in a5psw_flooding_set_resolution() would potentially messed up this.
> Use a read-modify-write to set that value and move bridged_ports
> handling in bridge_port_join/leave.
> 
> Signed-off-by: Clément Léger <clement.leger@...tlin.com>
> ---
>  drivers/net/dsa/rzn1_a5psw.c | 12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/net/dsa/rzn1_a5psw.c b/drivers/net/dsa/rzn1_a5psw.c
> index 919027cf2012..8b7d4a371f8b 100644
> --- a/drivers/net/dsa/rzn1_a5psw.c
> +++ b/drivers/net/dsa/rzn1_a5psw.c
> @@ -299,13 +299,9 @@ static void a5psw_flooding_set_resolution(struct a5psw *a5psw, int port,
>  			A5PSW_MCAST_DEF_MASK};
>  	int i;
>  
> -	if (set)
> -		a5psw->bridged_ports |= BIT(port);
> -	else
> -		a5psw->bridged_ports &= ~BIT(port);
> -
>  	for (i = 0; i < ARRAY_SIZE(offsets); i++)
> -		a5psw_reg_writel(a5psw, offsets[i], a5psw->bridged_ports);
> +		a5psw_reg_rmw(a5psw, offsets[i], BIT(port),
> +			      set ? BIT(port) : 0);
>  }
>  
>  static int a5psw_port_bridge_join(struct dsa_switch *ds, int port,
> @@ -326,6 +322,8 @@ static int a5psw_port_bridge_join(struct dsa_switch *ds, int port,
>  	a5psw_flooding_set_resolution(a5psw, port, true);
>  	a5psw_port_mgmtfwd_set(a5psw, port, false);
>  
> +	a5psw->bridged_ports |= BIT(port);
> +
>  	return 0;
>  }
>  
> @@ -334,6 +332,8 @@ static void a5psw_port_bridge_leave(struct dsa_switch *ds, int port,
>  {
>  	struct a5psw *a5psw = ds->priv;
>  
> +	a5psw->bridged_ports &= ~BIT(port);
> +
>  	a5psw_flooding_set_resolution(a5psw, port, false);
>  	a5psw_port_mgmtfwd_set(a5psw, port, true);
>  
> -- 
> 2.39.0
> 

What about the a5psw_flooding_set_resolution() call for the CPU port, from a5psw_setup()?
Isn't this an undocumented change? Does this logic in a5psw_port_bridge_leave() still work,
now that bridged_ports will no longer contain BIT(A5PSW_CPU_PORT)?

	/* No more ports bridged */
	if (a5psw->bridged_ports == BIT(A5PSW_CPU_PORT))
		a5psw->br_dev = NULL;