[PATCH net v4 1/7] net: dsa: mt7530: fix trapping frames with multiple CPU ports on MT7531

[Vladimir Oltean]

On Mon, Jun 12, 2023 at 10:59:39AM +0300, arinc9.unal at gmail.com wrote:
> From: Arınç ÜNAL <arinc.unal at arinc9.com>
> 
> Every bit of the CPU port bitmap for MT7531 and the switch on the MT7988
> SoC represents a CPU port to trap frames to. These switches trap frames
> received from a user port to the CPU port that is affine to the user port
> from which the frames are received.
> 
> Currently, only the bit that corresponds to the first found CPU port is set
> on the bitmap. When multiple CPU ports are being used, the trapped frames
> from the user ports not affine to the first CPU port will be dropped as the
> other CPU port is not set on the bitmap. The switch on the MT7988 SoC is
> not affected as there's only one port to be used as a CPU port.
> 
> To fix this, introduce the MT7531_CPU_PMAP macro to individually set the
> bits of the CPU port bitmap. Set the CPU port bitmap for MT7531 and the
> switch on the MT7988 SoC on mt753x_cpu_port_enable() which runs on a loop
> for each CPU port.
> 
> Add a comment to explain frame trapping for these switches.
> 
> According to the document MT7531 Reference Manual for Development Board
> v1.0, the MT7531_CPU_PMAP bits are unset after reset so no need to clear it
> beforehand. Since there's currently no public document for the switch on
> the MT7988 SoC, I assume this is also the case for this switch.
> 
> Fixes: c288575f7810 ("net: dsa: mt7530: Add the support of MT7531 switch")
> Signed-off-by: Arınç ÜNAL <arinc.unal at arinc9.com>
> ---

Would you agree that this is just preparatory work for change "net: dsa:
introduce preferred_default_local_cpu_port and use on MT7530" and not a
fix to an existing problem in the code base?