Re: [PATCH net-next v3 2/2] net: dsa: mv88e6xxx: add support for credit based shaper

[Luke Howard]

> On 28 May 2026, at 5:55 pm, Cedric Jehasse <cedric.jehasse@xxxxxxxxx> wrote:
> 
> On Thu, May 28, 2026 at 8:28 AM Luke Howard <lukeh@xxxxxxxx> wrote:
>> 
>> Hi Cedric,
>> 
>> One further comment: the Marvell DSDT reference implementation (GPLv2) also sets an undocumented register on the 6352 family of switches to enable CBS. (This does not apply to the 6390 family.)
>> 
>> My understanding is that you should call mv88e6xxx_port_qav_read(MV88E6352_PORT_QAV_CFG) and then set or unset MV88E6352_PORT_QAV_CFG_ENABLE accordingly.
>> 
>> The values are given below:
>> 
>> #define MV88E6352_PORT_QAV_CFG                    0x08
>> #define MV88E6352_PORT_QAV_CFG_ENABLE             0x8000
>> 
> 
> I'm wondering if this is needed.
> I can't find this in the UMSD, which is newer than the DSDT. Why was this
> removed by Marvell? And the register is undocumented.

That’s a strong argument it is not required. I’ll test tomorrow.

Luke