net: dsa: realtek: rtl8365mb: add HSGMII support for RTL8367S

In addition to SGMII, the RTL8367S SerDes also supports HSGMII, which
carries 2.5 Gbps with the same signaling as SGMII at 2.5x clock rate.
The chip info table already declares HSGMII as a supported interface
mode for external interface 1.

Extend the SerDes PCS to handle HSGMII, which phylink represents as
2500base-x:

 - Select the HSGMII SerDes tuning parameters and external interface
   mode, and mux the SerDes to MAC8 in HSGMII mode, from pcs_config()
   according to the interface. The parameters are again lifted from the
   GPL-licensed Realtek rtl8367c vendor driver, and again only cover
   the tuning variant for a non-zero chip option, so the mode is gated
   on the option probed at setup.

 - Advertise 2500base-x and MAC_2500FD on ports whose external
   interface supports HSGMII.

 - Accept SPEED_2500 in the forced link configuration. The MAC speed
   field has no 2.5 Gbps value: the rate is determined by the HSGMII
   SerDes configuration, and the vendor driver programs the 1 Gbps
   value here, so do the same.

 - Raise the port 6 ingress and egress rate limiters to their maximum
   at setup time, as the vendor switch init does unconditionally for
   the whole chip family. The chip resets them to 0x1FFFF (~1.048 Gbps
   in units of 8 Kbps), which caps the aggregate HSGMII throughput at
   roughly 1 Gbps. The vendor documentation describes the reset
   default as disabling the limiter, but the cap is real: on an
   RTL8367S-based Mercusys MR85X running an OpenWrt backport of this
   series, several clients on 1 Gbps user ports were limited to about
   1.02 Gbps combined across the HSGMII CPU port until these limiters
   were raised, after which throughput reached about 2 Gbps [1]. The
   related HSGMII scheduler line rate (LINE_RATE_HSG_H) is already set
   to its maximum by the common init jam table.

Tested on a Mercusys MR80X v2.20, where the RTL8367S is connected to
the SoC over HSGMII.

Link: https://github.com/openwrt/openwrt/pull/19445#issuecomment-4505613294 [1]
Suggested-by: Luiz Angelo Daros de Luca <luizluca@gmail.com>
Suggested-by: Mieczyslaw Nalewaj <namiltd@yahoo.com>
Signed-off-by: Johan Alvarado <contact@c127.dev>
Tested-by: Stanisław Pal <kuncy7@gmail.com>
Reviewed-by: Luiz Angelo Daros de Luca <luizluca@gmail.com>
Reviewed-by: Mieczyslaw Nalewaj <namiltd@yahoo.com>
Tested-by: Stanislaw Pal <kuncy7@gmail.com>
Link: https://patch.msgid.link/20260711-rtl8367s-sgmii-v6-2-88f7944ddca7@c127.dev
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

0 files changed, 0 insertions, 0 deletions