Re: [PATCH net-next] net: phy: broadcom: enable jumbo frames on BCM54xx

[Florian Fainelli]

On 9/14/26 02:47, Nicolai Buchwitz wrote:
> Jumbo packets need two bits that default to off, extended packet length in
> the auxiliary control register and PCS transmit FIFO elasticity in the
> extended control register. The latter raises the transmit limit from 4.5
> KB to 9 KB at the cost of 16 ns of 1000BASE-T transmit latency, and the
> two together take copper mode to 10 KB.
>
> Without them such frames are lost on a 100M link while the same frames
> pass at 1G. On a Raspberry Pi CM5, which uses a BCM54210PE, 9142 byte
> frames at 100M are lost 20 out of 20 with the MAC counting every one
> as transmitted. The same frames over the same path at 1G arrive intact.
>
> Set both, which bcm_phy_enable_jumbo() already does for bcm7xxx. The
> frames then arrive and the payloads check out byte for byte.
>
> Signed-off-by: Nicolai Buchwitz <nb@xxxxxxxxxxx>

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