Re: [PATCH net v3] net: phylink: treat PSGMII as an inband capable interface

[Paolo Abeni]

On 8/9/26 6:01 PM, Sandeep Sondagar wrote:
> PSGMII (the Qualcomm 5-port SGMII) conveys the link negotiation result
> from the PHY back to the MAC through per-channel in-band SGMII words,
> exactly like SGMII and QSGMII.
> 
> However, PHY_INTERFACE_MODE_PSGMII is missing from
> phylink_get_inband_type(), so phylink reports INBAND_NONE for it and
> phylink_pcs_neg_mode() falls back to PHYLINK_PCS_NEG_NONE. The PCS is
> then programmed in force mode and its control-register speed bits (which
> default to 1000base) are used, so a slower copper link - e.g. 100base-T
> - is reported as 1Gbps and cannot pass traffic.
> 
> Classify PSGMII alongside SGMII and QSGMII as INBAND_CISCO_SGMII so the
> PCS negotiates in-band and the resolved link speed comes from the PHY
> in-band word.
> 
> Also add PSGMII to the generic clause 22 PCS helper functions which
> handle the SGMII in-band word. Without this, a PCS using these helpers
> would still fall through to the default handling and force the link
> state to false in phylink_mii_c22_pcs_decode_state(), fail to encode
> the SGMII advertisement, and get rejected by phylink_get_link_timer_ns().
> 
> Fixes: 83b5f0253b1e ("net: phy: Introduce PSGMII PHY interface mode")
> Signed-off-by: Sandeep Sondagar <sandeepsondagar@xxxxxxxxx>
Sashiko noted no in-tree driver is affected. At very least, this should
go via the net-next tree without any fixes tag, but I'm wondering if we
want it at all?

@Andrew: WDYT?

Thanks,

Paolo