Re: Supporting SGMII to 100BaseFX SFP modules, with broadcom PHYs

Maxime Chevallier
2025-06-25T07:15:15Z

Hi again Florian,

On Tue, 24 Jun 2025 15:29:25 -0700
Florian Fainelli <florian.fainelli@broadcom.com> wrote:

> For 100BaseFX, the signal detection is configured in bit 5 of the shadow
> 0b01100 in the 0x1C register. You can use bcm_{read,write}_shadow() for
> that:
>
> 0 to use EN_10B/SD as CMOS/TTL signal detect (default)
> 1 to use SD_100FX± as PECL signal detect
>
> You can use either copper or SGMII interface for 100BaseFX and that will
> be configured this way:
>
> - in register 0x1C, shadow 0b10 (1000Base-T/100Base-TX/10Base-T Spare
> Control 1), set bit 4 to 1 to enable 100BaseFX
>
> - disable auto-negotiation with register 0x00 = 0x2100
>
> - set register 0x18 to 0x430 (bit 10 -> normal mode, bits 5:4 control
> the edge rate. 0b00 -> 4ns, 0b01 -> 5ns, 0b10 -> 3ns, 0b11 -> 0ns. This
> is the auxiliary control register (MII_BCM54XX_AUXCTL_SHDWSEL_AUXCTL).

And I have my first ping going through :) Thank you so much, if I get a
chance to meet you in person one day, drinks are on me :)

Thanks again,

Maxime