Re: [PATCH net-next 01/15] net: dsa: mt7530: always trap frames to active CPU port on MT7530

Russell King (Oracle)
2023-11-18T14:35:16Z

On Sat, Nov 18, 2023 at 03:31:51PM +0300, Arınç ÜNAL wrote:
> + /* Set the CPU port to trap frames to for MT7530. Trapped frames will be
> + * forwarded to the numerically smallest CPU port which the DSA conduit
> + * interface its affine to is up.
> + */
> + if (priv->id != ID_MT7530 && priv->id != ID_MT7621)
> + return;
> +
> + if (operational)
> + priv->active_cpu_ports |= BIT(cpu_dp->index);
> + else
> + priv->active_cpu_ports &= ~BIT(cpu_dp->index);
> +
> + if (priv->active_cpu_ports)
> + mt7530_rmw(priv, MT7530_MFC, CPU_EN | CPU_PORT_MASK, CPU_EN |
> + CPU_PORT(__ffs(priv->active_cpu_ports)));

I would be tempted to write this as:

mask = BIT(cpu_dp->index);

if (operational)
priv->active_cpu_ports |= mask;
else
priv->active_cpu_ports &= ~mask;

Now, what happens when active_cpu_ports is zero? Doesn't that mean there
is no active CPU port? In which case, wouldn't disabling the CPU port
direction be appropriate, such as:

if (priv->active_cpu_ports)
val = CPU_EN | CPU_PORT(__ffs(priv->active_cpu_ports));
else
val = 0;

mt7530_rmw(priv, MT7530_MFC, CPU_EN | CPU_PORT_MASK, val);

?

> struct mt7530_priv {
> struct device *dev;
> @@ -786,6 +787,7 @@ struct mt7530_priv {
> struct irq_domain *irq_domain;
> u32 irq_enable;
> int (*create_sgmii)(struct mt7530_priv *priv, bool dual_sgmii);
> + unsigned long active_cpu_ports;

So this will be 32 or 64 bit in size. Presumably you know how many CPU
ports there can be, which looking at this code must be less than 8 as
CPU_PORT_MASK is only 3 bits in size. So, maybe use a u8, and check
that cpu_dp->index <= 7 ?

I would also suggest moving irq_enable after create_sgmii, to avoid
holes in the struct.

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