Re: [PATCH net-next v2 13/14] net: stmmac: tc956x: add TC956x/QPS615 support

[Alex Elder <elder@riscstar.com>]

On 6/5/26 11:05 AM, Maxime Chevallier wrote:
> Hi Alex,
> 
> On 6/5/26 03:00, Alex Elder wrote:
>> From: Daniel Thompson <daniel@riscstar.com>
>>
>> Toshiba TC956x is an Ethernet AVB/TSN bridge and is essentially a
>> small and highly-specialized SoC. TC956x includes an "eMAC" subsystem
>> that can be accessed, along with several other peripherals, via two
>> PCIe endpoint functions. There is a main driver for the endpoint that
>> decomposes things and creates auxiliary bus devices to model the SoC.
>>
>> The eMAC consists of a Designware XGMAC, XPCS and PMA. Each eMAC is
>> supported by an MSIGEN that bridges TC956x level interrupts to PCIe
>> MSIs.
>>
>> Add a driver for the eMAC/MSIGEN combination.
>>
>> Co-developed-by: Alex Elder <elder@riscstar.com>
>> Signed-off-by: Alex Elder <elder@riscstar.com>
>> Signed-off-by: Daniel Thompson <daniel@riscstar.com>
>> ---
> [...]
> 
>> +static int tc956x_lookup_max_speed(phy_interface_t phy_interface)
>> +{
>> +	switch (phy_interface) {
>> +	case PHY_INTERFACE_MODE_SGMII:
> 
> The SGMII definition we use in the kernel is the Cisco SGMII de-facto
> standard that only supports 10/100/1000M. Some vendors use flavours with
> names such as HS-SGMII and such, that's basically SGMII clocked at 2.5G
> with aneg disabled. It kinda becomes 2500BaseX then.

So for SGMII then, the max speed returned/used should be
SPEED_1000, correct?  And for 2500BASEX it's SPEED_2500.
(I'll fix this.)

For USXGMII I presume we'd use SPEED_10000 as the max_speed.

Can someone explain when the plat_stmmacenet_data->max_speed value
must be set?  It seems like plat_stmmacenet_data->phy_interface
should normally imply the right maximum speed.  It looks like
phylink_interface_max_speed() has a big switch statement related
to this.

Thanks.

					-Alex

> So all in all, we don't support 2500M on SGMII.
> 
>> +	case PHY_INTERFACE_MODE_2500BASEX:
>> +		return SPEED_2500;
>> +
>> +	default:
>> +		return -EOPNOTSUPP;
>> +	}
> 
> Maxime