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Date:   Fri, 4 Aug 2023 14:04:02 +0200
From:   Andrew Lunn <andrew@lunn.ch>
To:     Choong Yong Liang <yong.liang.choong@linux.intel.com>
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Subject: Re: [PATCH net-next v2 0/5] TSN auto negotiation between 1G and 2.5G
Message-ID: <5bd05ba2-fd88-4e5c-baed-9971ff917484@lunn.ch>
References: <20230804084527.2082302-1-yong.liang.choong@linux.intel.com>
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On Fri, Aug 04, 2023 at 04:45:22PM +0800, Choong Yong Liang wrote:
> Intel platforms’ integrated Gigabit Ethernet controllers support
> 2.5Gbps mode statically using BIOS programming. In the current
> implementation, the BIOS menu provides an option to select between
> 10/100/1000Mbps and 2.5Gbps modes. Based on the selection, the BIOS
> programs the Phase Lock Loop (PLL) registers. The BIOS also read the
> TSN lane registers from Flexible I/O Adapter (FIA) block and provided
> 10/100/1000Mbps/2.5Gbps information to the stmmac driver. But
> auto-negotiation between 10/100/1000Mbps and 2.5Gbps is not allowed.
> The new proposal is to support auto-negotiation between 10/100/1000Mbps
> and 2.5Gbps . Auto-negotiation between 10, 100, 1000Mbps will use
> in-band auto negotiation. Auto-negotiation between 10/100/1000Mbps and
> 2.5Gbps will work as the following proposed flow, the stmmac driver reads
> the PHY link status registers then identifies the negotiated speed.
> Based on the speed stmmac driver will identify TSN lane registers from
> FIA then send IPC command to the Power Management controller (PMC)
> through PMC driver/API. PMC will act as a proxy to programs the
> PLL registers.

Have you considered using out of band for all link modes? You might
end up with a cleaner architecture, and not need any phylink/phylib
hacks.

	Andrew