linux-kernel - Re: [PATCH net-next 2/2] net: phy: broadcom: add 1000Base-X support for BCM54616S

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Message-ID: <08f55ccc-7d2a-996b-770b-a0f035889196@fb.com>
Date:   Wed, 31 Jul 2019 05:55:32 +0000
From:   Tao Ren <taoren@...com>
To:     Andrew Lunn <andrew@...n.ch>
CC:     Vladimir Oltean <olteanv@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Heiner Kallweit <hkallweit1@...il.com>,
        "David S . Miller" <davem@...emloft.net>,
        Arun Parameswaran <arun.parameswaran@...adcom.com>,
        Justin Chen <justinpopo6@...il.com>,
        netdev <netdev@...r.kernel.org>,
        lkml <linux-kernel@...r.kernel.org>,
        Andrew Jeffery <andrew@...id.au>,
        "openbmc@...ts.ozlabs.org" <openbmc@...ts.ozlabs.org>
Subject: Re: [PATCH net-next 2/2] net: phy: broadcom: add 1000Base-X support
 for BCM54616S

On 7/30/19 7:34 PM, Andrew Lunn wrote:
>> Hi Andrew,
>>
>> The BCM54616S PHY on my machine is connected to a BCM5396 switch chip over backplane (1000Base-KX).
> 
> Ah, that is different. So the board is using it for RGMII to 1000Base-KX?
> 
> phy-mode is about the MAC-PHY link. So in this case RGMII.

Yes. It's RGMII to 1000Base-KX.

> There is no DT way to configure the PHY-Switch link. However, it
> sounds like you have the PHY strapped so it is doing 1000BaseX on the
> PHY-Switch link. So do you actually need to configure this?

The PHY is strapped in RGMII-Fiber Mode (the term used in datasheet), but besides 1000BaseX, 100Base-FX is also supported in this mode.
The datasheet doesn't say which link type (1000BaseX or 100Base-FX) is active after reset and I cannot find a way to auto-detect the link type, either.

Below are a few more details about 1000Base-X and 100Base-FX in BCM54616S datasheet.

- 1000BaseX: 
  The 1000BaseX register set (MII registers 00-0F) needs to be enabled by setting bit 0 of Mode Control Register.
  Although the register address is the same between 1000BaseX and 1000BaseT/100BaseT/10BaseT registers, some bit fields in 1000BaseX registers are different: for example, speed field is not available in 1000BaseX status register.

- 100Base-FX:
  100Base-FX registers need to be enabled by writing 1 to SerDes 100FX Control Register.
  100Base-FX Control and Status registers are in shadow register 1Ch, instead of MII register 00h and 01h.

> You report you never see link up? So maybe the problem is actually in
> read_status? When in 1000BaseX mode, do you need to read the link
> status from some other register? The Marvell PHYs use a second page
> for 1000BaseX.

read_status callback needs to be updated to report correct link speed in my case. But as I cannot tell which link type (1000BaseX or 100Base-FX) is active, it becomes hard to access registers in read_status method. Any suggestions?

BTW, link-never-up issue seems to be caused by static/dynamic feature detection. I'm still tracing down the issue and it's being tracked in patch #1 of the series.


Thanks,

Tao