Re: [PATCH net] net: bcmgenet: cap the Tx queue threshold at the ring size

[Florian Fainelli]

On 11/6/2026 6:10 AM, Nicolai Buchwitz wrote:
> A Tx queue stops when MAX_SKB_FRAGS + 1 or fewer descriptors are free and
> wakes once there are more. Queues 1 to 4 hold 32 descriptors, so with
> CONFIG_MAX_SKB_FRAGS at 31 they would need 33 to wake. As a result the
> first packet stops the queue and it stays stopped:
>
>    eth0: NETDEV WATCHDOG: CPU: 0: transmit queue 3 timed out 2004 ms
>    eth0: NETDEV WATCHDOG: CPU: 1: transmit queue 4 timed out 2004 ms
>
> On a Raspberry Pi CM4 only queue 0 carried traffic afterwards. The other
> four counted an error on nearly every packet.
>
> Fix this and cap the threshold at what the ring can free.
>
> Fixes: 3948b05950fd ("net: introduce a config option to tweak MAX_SKB_FRAGS")
> Signed-off-by: Nicolai Buchwitz <nb@xxxxxxxxxxx>

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

Eventually we will have to decide what to do with those other queues :D
--
Florian