Re: [PATCH net v2] net: macb: rate limit netdev error info print in the data path

[Nicolai Buchwitz]

Hi Zijin

On 30.9.2026 13:35, taozj888@xxxxxxx wrote:
> From: taozijin <taozj888@xxxxxxx>
>
> Now the MACB ethernet driver print the netdev error information
> directly by netdev_err(), which would lead to a large number of
> error information print if there was a significant number of
> error or just jumbo packets exceeding the MTU received when booting.
> For example, it would print a large number of:
>
> macb PHYT0036:00 eth0: not whole frame pointed by descriptor
> macb PHYT0036:00 eth0: not whole frame pointed by descriptor
> ...

Out of interest: Is this a Phytium vendor kernel?

> in gem_rx() by received a large number of packets without
> RX_EOF flag set, especially with unknown packet
> type that would penetrate the hardware offload for the IP packets.
>
> The unlimited prints here would greatly bother and delay
> the system booting process unless the source stop sending
> packets since they occupy the console output bandwidth and
> other processes have to wait for the completion of printing those
> messages.
>
> So rate limit the netdev error information print in the receive
> and transmit data path.
>
> Fixes: 89e5785fc8a6 ("[PATCH] Atmel MACB ethernet driver")

IMHO the correct tag is 4df95131ea80 ("net/macb: change RX path for 
GEM")?
At least the gem_rx() messages were introduced here.

> Cc: stable@xxxxxxxxxxxxxxx

Drop the blank line as otherwise tooling might get confused and doesn't
get all tags correctly.

> Signed-off-by: Zijin Tao <taozj888@xxxxxxx>
> ---
>  drivers/net/ethernet/cadence/macb_main.c | 14 ++++++++------
>  1 file changed, 8 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/net/ethernet/cadence/macb_main.c 
> b/drivers/net/ethernet/cadence/macb_main.c
> index 8e5c034dc3a4..ca60960bec36 100644
> --- a/drivers/net/ethernet/cadence/macb_main.c
> +++ b/drivers/net/ethernet/cadence/macb_main.c
> @@ -1617,16 +1617,16 @@ static int gem_rx(struct macb_queue *queue, 
> struct napi_struct *napi,
>  		count++;
>
>  		if (!(ctrl & MACB_BIT(RX_SOF) && ctrl & MACB_BIT(RX_EOF))) {
> -			netdev_err(bp->netdev,
> -				   "not whole frame pointed by descriptor\n");
> +			if (net_ratelimit())
> +				netdev_err(bp->netdev, "not whole frame pointed by descriptor\n");

This will just hide the error message, but the split/drop is still 
present.
How about limiting JML in macb_init_hw() properly?

        if ((bp->caps & MACB_CAPS_JUMBO) && bp->jumbo_max_len) {
                u32 jml = bp->rx_buffer_size - NET_IP_ALIGN + 
ETH_FCS_LEN;
                gem_writel(bp, JML, min(jml, bp->jumbo_max_len));
        }

The code above is untested, so probably needs further tweaking. An 
alternative could
be to handle the split frames in gem_rx() correctly.

> [...]

Thanks,
Nicolai