Re: [PATCH phy-next 5/5] phy: lynx-28g: add support for 25GBASER

[Josua Mayer]

Am 11.05.26 um 17:00 schrieb Vladimir Oltean:
> From: Ioana Ciornei <ioana.ciornei@xxxxxxx>
>
> Add support for 25GBASE-R in the Lynx 28G SerDes PHY driver. This will
> be used by the dpaa2-mac consumer on LX2160A with:
> - phy_validate(phy, PHY_MODE_ETHERNET, PHY_INTERFACE_MODE_25GBASER) to
>   detect support.
> - phy_set_mode_ext(phy, PHY_MODE_ETHERNET, PHY_INTERFACE_MODE_25GBASER)
>   to reconfigure the lane for this protocol.
>
> The intended use case for dynamic protocol switching to 25GBase-R is
> with SFP28 modules, and protocol switching is triggered by the SFP
> module insertion. There also exists a 25GBase-KR use case, where the
> protocol switching is covered by IEEE 802.3 clause 73 auto-negotiation.
> However, that is not handled here; it merely needs the support added
> here as basic ground work.
>
> The lane frequency for 25GbE is sourced from a clock net frequency of
> 12.890625 GHz, as produced by PLLF or PLLS, further multiplied by the
> lane by 2. The clock net frequencies produced by the PLLs are treated as
> read-only by the driver, so the absence of a PLL provisioned for the
> right clock net frequency implies absence of 25GbE support, even though
> a lane might have the appropriate protocol converter for it.
>
> In terms of implementation, the change consists of:
> - determining at probe time if any PLL was preconfigured for the
>   required clock net frequency for 25GbE
> - adding the default lane parameters for reconfiguring a lane to 25GbE
>   irrespective of the original protocol
> - allowing this operating mode only on supported lanes, i.e. all lanes
>   of LX2162A SerDes #1, and LX2160A SerDes lanes 0-1, 4-7.
>
> Signed-off-by: Ioana Ciornei <ioana.ciornei@xxxxxxx>
> Signed-off-by: Vladimir Oltean <vladimir.oltean@xxxxxxx>
> ---
> Change previously submitted at:
> https://lore.kernel.org/linux-phy/20260114152111.625350-6-vladimir.oltean@xxxxxxx/
>
> Changes:
> - reword commit message
> ---
>  drivers/phy/freescale/phy-fsl-lynx-28g.c | 90 +++++++++++++++++++++++-
>  1 file changed, 88 insertions(+), 2 deletions(-)

In order to test this patch with 25Gbps link, additional changes on other drivers are needed.
This is not a short-coming of this patch.

1. I tested this patch-set alone on LX2162 Clearfog with SD1 Protocl 18 (i.e. 2x 10G SFP, 2x 25G SFP):

10Gbps ports are working fine!

25Gbps fail to probe (but this is partly expected):

[    8.373048] fsl_dpaa2_eth dpni.9 (unnamed net_device) (uninitialized): MAC returned PCS which does not support 25gbase-r
[    8.373065] fsl_dpaa2_eth dpni.9 (unnamed net_device) (uninitialized): MAC returned PCS which does not support 25gbase-r
[    8.373074] fsl_dpaa2_eth dpni.9 (unnamed net_device) (uninitialized): failed to validate link configuration for in-band status
[    8.373078] fsl_dpaa2_eth dpni.9 (unnamed net_device) (uninitialized): Error connecting to the MAC endpoint: -EINVAL
[    8.725004] fsl_dpaa2_eth dpni.9: probe with driver fsl_dpaa2_eth failed with error -22
[    8.920766] fsl_dpaa2_eth dpni.8 (unnamed net_device) (uninitialized): MAC returned PCS which does not support 25gbase-r
[    8.920783] fsl_dpaa2_eth dpni.8 (unnamed net_device) (uninitialized): MAC returned PCS which does not support 25gbase-r
[    8.920791] fsl_dpaa2_eth dpni.8 (unnamed net_device) (uninitialized): failed to validate link configuration for in-band status
[    8.920795] fsl_dpaa2_eth dpni.8 (unnamed net_device) (uninitialized): Error connecting to the MAC endpoint: -EINVAL
[    9.290005] fsl_dpaa2_eth dpni.8: probe with driver fsl_dpaa2_eth failed with error -22

Perhaps driver could switch to 10G instead? However not important in my opinion.

2. Tested with additional out of tree patches:

net: phylink: extend phylink_mii_c45_pcs_get_state also for PHY_INTERFACE_MODE_25GBASER
net: pcs: lynx: extend support to also handle PHY_INTERFACE_MODE_25GBASER

Then insert 10Gbps SFP module and link-up + TX/RX working fine!
I.e. driver switched successfully from 25Gbps configuration to 10Gbps.

Then insert 25Gbps SFP module. Errors start occuring:

[  357.043894] fsl_dpaa2_eth dpni.9 eth2: Link is Down
[  357.941036] sfp sfp-bt: module removed
[  364.269580] sfp sfp-bt: module FS               SFP-25GSL-85     rev 1A   sn C2501330127      dc 250203  
[  364.269625] fsl_dpaa2_eth dpni.9 eth2: switched to inband/25gbase-r link mode
[  364.271674] fsl_dpaa2_eth dpni.9 eth2: phy_set_mode_ext() = -95
[  364.293232] hwmon hwmon8: temp1_input not attached to any thermal zone

The link starts flapping, which is likely due to a combination of:

1. the lane has been halted but not stopped
2. the lane is still configured for 10G speed
3. the retimer (not supported by kernel) is still configured for 10G speed

[  364.333777] fsl_dpaa2_eth dpni.9 eth2: Link is Up - 25Gbps/Full - flow control off
[  365.280234] fsl_dpaa2_eth dpni.9 eth2: Link is Down
[  365.287750] fsl_dpaa2_eth dpni.9 eth2: Link is Up - 25Gbps/Full - flow control off
[  366.304434] fsl_dpaa2_eth dpni.9 eth2: Link is Down
[  366.311868] fsl_dpaa2_eth dpni.9 eth2: Link is Up - 25Gbps/Full - flow control off
[  367.328306] fsl_dpaa2_eth dpni.9 eth2: Link is Down
...

So I reconfigure the retimer by i2cset for 25Gbps speed, and link goes down permanently.

root@localhost:~# ethtool eth2
Settings for eth2:
        Supported ports: [ FIBRE ]
        Supported link modes:   25000baseSR/Full
        Supported pause frame use: Symmetric Receive-only
        Supports auto-negotiation: No
        Supported FEC modes: Not reported
        Advertised link modes:  Not reported
        Advertised pause frame use: No
        Advertised auto-negotiation: No
        Advertised FEC modes: Not reported
        Speed: Unknown!
        Duplex: Half
        Auto-negotiation: off
        Port: FIBRE
        PHYAD: 0
        Transceiver: internal
        Link detected: no

I would give this a partial tested-by, considering it switched successfully to 10G,
but failed switching to 25G, which is new with this patch. and needs extra patches.