netdev - Re: HW question: i210 vs. BCM5461S over SGMII: no response from PHY to MDIO requests?

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Message-ID: <5AB0F842.2769.43BFD896@Frantisek.Rysanek.post.cz>
Date:   Tue, 20 Mar 2018 13:02:10 +0100
From:   "Frantisek Rysanek" <Frantisek.Rysanek@...t.cz>
To:     Andrew Lunn <andrew@...n.ch>, netdev@...r.kernel.org
Subject: Re: HW question: i210 vs. BCM5461S over SGMII: no response from PHY to MDIO requests?

I've taken a look inside the two SFP's.
http://support.fccps.cz/download/adv/frr/ptp/inside_sfps.zip

The uglier, bigger and likely older model (my SFP#2) contains two 
PCB's sandwiched, and the key chips are inside the sandwich.
Thus, the photoes don't show much.

The sexier SFP#1 = the one with the Broadcom chip... I believe it's 
what it says on the tin:

- the BCM5461SA is directly interfaced to a laser driver chip (pretty 
much analog, found a datasheet from Maxim)

- the RX direction seems equally simple, I haven't identified the 
chip by the marking, but by pinout it's undoubtedly an RX amplifier 
(they're called transimpedance amps, are they?) and, looking at the 
PCB traces, its output is directly interfaced to the BCM5461SA.

- there's another BGA chip on the board, smaller than the BCM PHY. 
I believe that this is an "SFP MCU". Might be from Maxim or from 
someone completely different :-) Not sure whose trademark the "+" 
sign is in the chip marking.

I've found a *slightly* more promising "data brief" from Broadcom
for the BCM5461S:
http://infiber.ru/assets/files/products/phy/BCM5461S_Product_Brief.pdf
This one mentions 100Base-FX among the interface formats supported.

I don't believe that the SFP maker would pipe copper MLT3 into the 
fiber driver+receiver :-) Note that the block diagram in the Broadcom 
PDF contains other minor errors. God knows what the true 
functionality is.

The SFP#1 PCB still doesn't look fake to me.

Frank