netdev - Re: b53 tags on bpi-r1 (bcm53125)

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Date:   Tue, 21 Nov 2017 23:37:50 +0100
From:   scram287@...am.de
To:     Florian Fainelli <f.fainelli@...il.com>
Cc:     netdev@...r.kernel.org, Jochen Friedrich <jochen@...am.de>
Subject: Re: b53 tags on bpi-r1 (bcm53125)

Hi Florian,

> Hi Jochen,
>
> On 11/21/2017 12:10 AM, Jochen Friedrich wrote:
>> Hi Florian,
>>
>>
>> i just tested the latest DSA patches for b53 on a bpi-r1 device (net:
>> dsa: b53: Turn on Broadcom tags).
>>
>> Unfortunately, the bcm53125 does not seem to handle the broadcom tags on
>> CPU port although tuned on b53_brcm_hdr_setup(). The tag is still
>> visible on a device connected to one of the switch ports.
>>
>> I wonder if there is something else necessary to make the chip handle
>> the tags or if the chip doesn't support broadcom tags after all. The
>> documentation at
>> https://sourceforge.net/p/ohvesw/svn/12/tree/document/bcm/53125U-DS02-R.pdf
>> doesn't document register 3 in the management page, at all...
>
> I am afraid U stands for unmanaged, which means we may not have any
> possibility to enable Broadcom tags on that particular model. And you
> are right, I also don't see any Broadcom HDR control register in the
> datasheet, only the 53125M and S seem to have that, darn.

I had a closer look at the board, and it really has the 53125S  
soldered. The U datasheet seems to be the only one publically  
available though.

> Does the following patch help at all (I don't really expect it to)?

The patch doesn't make a difference, unfortunately.

> Could you also provide me with two piieces of information that could
> help detect such a switch model:
>
> - what is the value of the revision register (should be printed along
> with BCM53125 during boot)?

b53_common: found switch: BCM53125, rev 4

> - what is the value of page 02, register 3 during b53_switch_detect()? A
> managed switch should have this set to 0x3, whereas I would expect an
> unmanaged switch to be 0x0

I'll check this and tell you.

Thanks, Jochen