Re: [PATCH v2 1/6] ethdev: support setting lanes

[Thomas Monjalon <thomas@monjalon.net>]

26/03/2024 02:42, lihuisong (C):
> 
> 在 2024/3/25 17:30, Thomas Monjalon 写道:
> > 25/03/2024 07:24, huangdengdui:
> >> On 2024/3/22 21:58, Thomas Monjalon wrote:
> >>> 22/03/2024 08:09, Dengdui Huang:
> >>>> -#define RTE_ETH_LINK_SPEED_10G     RTE_BIT32(8)  /**< 10 Gbps */
> >>>> -#define RTE_ETH_LINK_SPEED_20G     RTE_BIT32(9)  /**< 20 Gbps */
> >>>> -#define RTE_ETH_LINK_SPEED_25G     RTE_BIT32(10) /**< 25 Gbps */
> >>>> -#define RTE_ETH_LINK_SPEED_40G     RTE_BIT32(11) /**< 40 Gbps */
> >>>> -#define RTE_ETH_LINK_SPEED_50G     RTE_BIT32(12) /**< 50 Gbps */
> >>>> -#define RTE_ETH_LINK_SPEED_56G     RTE_BIT32(13) /**< 56 Gbps */
> >>>> -#define RTE_ETH_LINK_SPEED_100G    RTE_BIT32(14) /**< 100 Gbps */
> >>>> -#define RTE_ETH_LINK_SPEED_200G    RTE_BIT32(15) /**< 200 Gbps */
> >>>> -#define RTE_ETH_LINK_SPEED_400G    RTE_BIT32(16) /**< 400 Gbps */
> >>>> +#define RTE_ETH_LINK_SPEED_10G            RTE_BIT32(8)  /**< 10 Gbps */
> >>>> +#define RTE_ETH_LINK_SPEED_20G            RTE_BIT32(9)  /**< 20 Gbps 2lanes */
> >>>> +#define RTE_ETH_LINK_SPEED_25G            RTE_BIT32(10) /**< 25 Gbps */
> >>>> +#define RTE_ETH_LINK_SPEED_40G            RTE_BIT32(11) /**< 40 Gbps 4lanes */
> >>>> +#define RTE_ETH_LINK_SPEED_50G            RTE_BIT32(12) /**< 50 Gbps */
> >>>> +#define RTE_ETH_LINK_SPEED_56G            RTE_BIT32(13) /**< 56 Gbps 4lanes */
> >>>> +#define RTE_ETH_LINK_SPEED_100G           RTE_BIT32(14) /**< 100 Gbps */
> >>>> +#define RTE_ETH_LINK_SPEED_200G           RTE_BIT32(15) /**< 200 Gbps 4lanes */
> >>>> +#define RTE_ETH_LINK_SPEED_400G           RTE_BIT32(16) /**< 400 Gbps 4lanes */
> >>>> +#define RTE_ETH_LINK_SPEED_10G_4LANES     RTE_BIT32(17)  /**< 10 Gbps 4lanes */
> >>>> +#define RTE_ETH_LINK_SPEED_50G_2LANES     RTE_BIT32(18) /**< 50 Gbps 2 lanes */
> >>>> +#define RTE_ETH_LINK_SPEED_100G_2LANES    RTE_BIT32(19) /**< 100 Gbps 2 lanes */
> >>>> +#define RTE_ETH_LINK_SPEED_100G_4LANES    RTE_BIT32(20) /**< 100 Gbps 4lanes */
> >>>> +#define RTE_ETH_LINK_SPEED_200G_2LANES    RTE_BIT32(21) /**< 200 Gbps 2lanes */
> >>>> +#define RTE_ETH_LINK_SPEED_400G_8LANES    RTE_BIT32(22) /**< 400 Gbps 8lanes */
> >>> I don't think it is a good idea to make this more complex.
> >>> It brings nothing as far as I can see, compared to having speed and lanes separated.
> >>> Can we have lanes information a separate value? no need for bitmask.
> >>>
> >> Hi,Thomas, Ajit, roretzla, damodharam
> >>
> >> I also considered the option at the beginning of the design.
> >> But this option is not used due to the following reasons:
> >> 1. For the user, ethtool couples speed and lanes.
> >> The result of querying the NIC capability is as follows:
> >> Supported link modes:
> >>          100000baseSR4/Full
> >>          100000baseSR2/Full
> >> The NIC capability is configured as follows:
> >> ethtool -s eth1 speed 100000 lanes 4 autoneg off
> >> ethtool -s eth1 speed 100000 lanes 2 autoneg off
> >>
> >> Therefore, users are more accustomed to the coupling of speed and lanes.
> >>
> >> 2. For the PHY, When the physical layer capability is configured through the MDIO,
> >> the speed and lanes are also coupled.
> >> For example:
> >> Table 45–7—PMA/PMD control 2 register bit definitions[1]
> >> PMA/PMD type selection
> >>                          1 0 0 1 0 1 0 = 100GBASE-SR2 PMA/PMD
> >>                          0 1 0 1 1 1 1 = 100GBASE-SR4 PMA/PMD
> >>
> >> Therefore, coupling speeds and lanes is easier to understand.
> >> And it is easier for the driver to report the support lanes.
> >>
> >> In addition, the code implementation is compatible with the old version.
> >> When the driver does not support the lanes setting, the code does not need to be modified.
> >>
> >> So I think the speed and lanes coupling is better.
> > I don't think so.
> > You are mixing hardware implementation, user tool, and API.
> > Having a separate and simple API is cleaner and not more difficult to handle
> > in some get/set style functions.
> Having a separate and simple API is cleaner. It's good.
> But supported lane capabilities have a lot to do with the specified 
> speed. This is determined by releated specification.
> If we add a separate API for speed lanes, it probably is hard to check 
> the validity of the configuration for speed and lanes.
> And the setting lane API sepparated from speed is not good for 
> uniforming all PMD's behavior in ethdev layer.

Please let's be more specific.
There are 3 needs:
	- set PHY lane config
	- get PHY lane config
	- get PHY lane capabilities

There is no problem providing a function to get the number of PHY lanes.
It is possible to set PHY lanes number after defining a fixed speed.

> The patch[1] is an example for this separate API.
> I think it is not very good. It cannot tell user and PMD the follow points:
> 1) user don't know what lanes should or can be set for a specified speed 
> on one NIC.

This is about capabilities.
Can we say a HW will support a maximum number of PHY lanes in general?
We may need to associate the maximum speed per lane?
Do we really need to associate PHY lane and PHY speed numbers for capabilities?
Example: if a HW supports 100G-4-lanes and 200G-2-lanes,
may we assume it is also supporting 200G-4-lanes?

> 2) how should PMD do for a supported lanes in their HW?

I don't understand this question. Please rephrase.

> Anyway, if we add setting speed lanes feature, we must report and set 
> speed and lanes capabilities for user well.
> otherwise, user will be more confused.

Well is not necessarily exposing all raw combinations as ethtool does.

> [1] https://patchwork.dpdk.org/project/dpdk/list/?series=31606