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

[Vladimir Oltean]

On Wed, May 13, 2026 at 11:37:14AM +0000, Josua Mayer wrote:
> 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

-95 is -EOPNOTSUPP. Is it coming from lynx_28g_set_mode()? If it is,
I suppose it is from lynx_28g_supports_lane_mode() returning false.

Assuming your list of additional patches is exhaustive, I think you
missed from patch 4/5:

 For old device trees with just "fsl,lynx-28g", the only things that
 change are:
 (...)

 - the feature set is frozen in time (e.g. no 25GbE). Since we cannot
   guarantee that this protocol will work on a lane, just err on the safe
   side and don't offer it (and require a device tree update to get it).

You can look at my branch
https://github.com/vladimiroltean/linux/commits/net-phy-upstreaming,
specifically commit "arm64: dts: lx2160a: transition to device-specific
SerDes compatible strings".