netdev - Re: [PATCH net 1/3] net: dsa: b53: fix enabling ip multicast

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Message-ID: <bde27b59-1169-4364-bc5e-a2a29d842d08@broadcom.com>
Date: Sun, 2 Nov 2025 08:53:15 -0800
From: Florian Fainelli <florian.fainelli@...adcom.com>
To: Jonas Gorski <jonas.gorski@...il.com>, Andrew Lunn <andrew@...n.ch>,
 Vladimir Oltean <olteanv@...il.com>, "David S. Miller"
 <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
 Vivien Didelot <vivien.didelot@...il.com>
Cc: Florian Fainelli <f.fainelli@...il.com>, netdev@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH net 1/3] net: dsa: b53: fix enabling ip multicast

On 11/2/2025 2:07 AM, Jonas Gorski wrote:
> In the New Control register bit 1 is either reserved, or has a different
> function:
> 
>      Out of Range Error Discard
> 
>      When enabled, the ingress port discards any frames
>      if the Length field is between 1500 and 1536
>      (excluding 1500 and 1536) and with good CRC.
> 
> The actual bit for enabling IP multicast is bit 0, which was only
> explicitly enabled for BCM5325 so far.
> 
> For older switch chips, this bit defaults to 0, so we want to enable it
> as well, while newer switch chips default to 1, and their documentation
> says "It is illegal to set this bit to zero."

The IP_MC bit is definitively a better name and matches what exists in 
the newer switching IP, it does default to 1 there as well, and it has 
the mention that it is illegal to set to zero (makes you wonder why it 
is exposed then).

> 
> So drop the wrong B53_IPMC_FWD_EN define, enable the IP multicast bit
> also for other switch chips. While at it, rename it to (B53_)IP_MC as
> that is how it is called in Broadcom code.
> 
> Fixes: 63cc54a6f073 ("net: dsa: b53: Fix egress flooding settings")
> Signed-off-by: Jonas Gorski <jonas.gorski@...il.com>

Reviewed-by: Florian Fainelli <florian.fainelli@...adcom.com>
-- 
Florian