On Tue, Jun 28, 2022 at 04:30:10PM +0200, Christian Marangi wrote:
> commit 386228c694bf1e7a7688e44412cb33500b0ac585 upstream.
>
> It was discovered that the Documentation lacks of a fundamental detail
> on how to correctly change the MAX_FRAME_SIZE of the switch.
>
> In fact if the MAX_FRAME_SIZE is changed while the cpu port is on, the
> switch panics and cease to send any packet. This cause the mgmt ethernet
> system to not receive any packet (the slow fallback still works) and
> makes the device not reachable. To recover from this a switch reset is
> required.
>
> To correctly handle this, turn off the cpu ports before changing the
> MAX_FRAME_SIZE and turn on again after the value is applied.
>
> Fixes: f58d2598cf70 ("net: dsa: qca8k: implement the port MTU callbacks")
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Christian Marangi <ansuelsmth@xxxxxxxxx>
> Link: https://lore.kernel.org/r/20220621151122.10220-1-ansuelsmth@xxxxxxxxx
> Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
> [ backport: fix conflict using the old port_sts struct instead of bitmap ]
Cc Greg wonder if this has some problems or I pushed it badly? (first
time I try to push a fixed backport)
> ---
> drivers/net/dsa/qca8k.c | 23 +++++++++++++++++++++--
> 1 file changed, 21 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/dsa/qca8k.c b/drivers/net/dsa/qca8k.c
> index a984f06f6f04..67869c8cbeaa 100644
> --- a/drivers/net/dsa/qca8k.c
> +++ b/drivers/net/dsa/qca8k.c
> @@ -1599,7 +1599,7 @@ static int
> qca8k_port_change_mtu(struct dsa_switch *ds, int port, int new_mtu)
> {
> struct qca8k_priv *priv = ds->priv;
> - int i, mtu = 0;
> + int ret, i, mtu = 0;
>
> priv->port_mtu[port] = new_mtu;
>
> @@ -1607,8 +1607,27 @@ qca8k_port_change_mtu(struct dsa_switch *ds, int port, int new_mtu)
> if (priv->port_mtu[i] > mtu)
> mtu = priv->port_mtu[i];
>
> + /* To change the MAX_FRAME_SIZE the cpu ports must be off or
> + * the switch panics.
> + * Turn off both cpu ports before applying the new value to prevent
> + * this.
> + */
> + if (priv->port_sts[0].enabled)
> + qca8k_port_set_status(priv, 0, 0);
> +
> + if (priv->port_sts[6].enabled)
> + qca8k_port_set_status(priv, 6, 0);
> +
> /* Include L2 header / FCS length */
> - return qca8k_write(priv, QCA8K_MAX_FRAME_SIZE, mtu + ETH_HLEN + ETH_FCS_LEN);
> + ret = qca8k_write(priv, QCA8K_MAX_FRAME_SIZE, mtu + ETH_HLEN + ETH_FCS_LEN);
> +
> + if (priv->port_sts[0].enabled)
> + qca8k_port_set_status(priv, 0, 1);
> +
> + if (priv->port_sts[6].enabled)
> + qca8k_port_set_status(priv, 6, 1);
> +
> + return ret;
> }
>
> static int
> --
> 2.36.1
>
--
Ansuel
