Re: [PATCH net-next v2 0/5] TSN auto negotiation between 1G and 2.5G

[Choong Yong Liang <yong.liang.choong@linux.intel.com>]

On 4/8/2023 8:04 pm, Andrew Lunn wrote:
> On Fri, Aug 04, 2023 at 04:45:22PM +0800, Choong Yong Liang wrote:
>> Intel platforms’ integrated Gigabit Ethernet controllers support
>> 2.5Gbps mode statically using BIOS programming. In the current
>> implementation, the BIOS menu provides an option to select between
>> 10/100/1000Mbps and 2.5Gbps modes. Based on the selection, the BIOS
>> programs the Phase Lock Loop (PLL) registers. The BIOS also read the
>> TSN lane registers from Flexible I/O Adapter (FIA) block and provided
>> 10/100/1000Mbps/2.5Gbps information to the stmmac driver. But
>> auto-negotiation between 10/100/1000Mbps and 2.5Gbps is not allowed.
>> The new proposal is to support auto-negotiation between 10/100/1000Mbps
>> and 2.5Gbps . Auto-negotiation between 10, 100, 1000Mbps will use
>> in-band auto negotiation. Auto-negotiation between 10/100/1000Mbps and
>> 2.5Gbps will work as the following proposed flow, the stmmac driver reads
>> the PHY link status registers then identifies the negotiated speed.
>> Based on the speed stmmac driver will identify TSN lane registers from
>> FIA then send IPC command to the Power Management controller (PMC)
>> through PMC driver/API. PMC will act as a proxy to programs the
>> PLL registers.
> 
> Have you considered using out of band for all link modes? You might
> end up with a cleaner architecture, and not need any phylink/phylib
> hacks.
> 
> 	Andrew
Hi Andrew,

After conducting a comprehensive study, it seems that implementing 
out-of-band for all link modes might not be feasible. I may have missed 
some key aspects during my analysis.

Would you be open to sharing a high-level idea of how we could potentially 
make this feasible? Your insights would be greatly appreciated.

By the way, I've submitted a new design that not exposing phylink's AN mode 
into phylib. Please help review it to determine if it is acceptable.