Messages in this thread | | | Date | Mon, 20 Jun 2022 21:56:19 -0700 | From | Jakub Kicinski <> | Subject | Re: [RESEND net-next PATCH 3/3] net: dsa: qca8k: reset cpu port on MTU change |
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On Sat, 18 Jun 2022 09:26:50 +0200 Christian Marangi wrote: > 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") > Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
It reads like this patch should be backported to 5.10 and 5.15 stable branches. While patches 1 and 2 are cleanups. In which case you should reports just patch 3 against net/master first, we'll send it to Linus at the end of the week and then you can send the cleanups on top for -next.
One extra question below.
> diff --git a/drivers/net/dsa/qca8k.c b/drivers/net/dsa/qca8k.c > index eaaf80f96fa9..0b92b9d5954a 100644 > --- a/drivers/net/dsa/qca8k.c > +++ b/drivers/net/dsa/qca8k.c > @@ -2334,6 +2334,7 @@ static int > qca8k_port_change_mtu(struct dsa_switch *ds, int port, int new_mtu) > { > struct qca8k_priv *priv = ds->priv; > + int ret; > > /* We have only have a general MTU setting. > * DSA always set the CPU port's MTU to the largest MTU of the slave > @@ -2344,10 +2345,29 @@ qca8k_port_change_mtu(struct dsa_switch *ds, int port, int new_mtu) > if (!dsa_is_cpu_port(ds, port)) > return 0; > > + /* 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_enabled_map & BIT(0)) > + qca8k_port_set_status(priv, 0, 0); > + > + if (priv->port_enabled_map & BIT(6)) > + qca8k_port_set_status(priv, 6, 0); > + > /* Include L2 header / FCS length */ > - return regmap_update_bits(priv->regmap, QCA8K_MAX_FRAME_SIZE_REG, > - QCA8K_MAX_FRAME_SIZE_MASK, > - new_mtu + ETH_HLEN + ETH_FCS_LEN); > + ret = regmap_update_bits(priv->regmap, QCA8K_MAX_FRAME_SIZE_REG,
Why care about the return code of this regmap access but not the ones inside the *port_set_status() calls?
> + QCA8K_MAX_FRAME_SIZE_MASK, > + new_mtu + ETH_HLEN + ETH_FCS_LEN); > + > + if (priv->port_enabled_map & BIT(0)) > + qca8k_port_set_status(priv, 0, 1); > + > + if (priv->port_enabled_map & BIT(6)) > + qca8k_port_set_status(priv, 6, 1); > + > + return ret; > } > > static int
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