netdev - Re: [PATCH net-next 0/2] net: mediatek: Add MT7621 TRGMII mode support

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Message-ID: <7f2fc770-1787-72f8-b91d-e2b12e74d39e@gmail.com>
Date:   Mon, 17 Jun 2019 19:21:26 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Andrew Lunn <andrew@...n.ch>,
        René van Dorst <opensource@...rst.com>
Cc:     Sean Wang <sean.wang@...iatek.com>,
        "David S . Miller" <davem@...emloft.net>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Vivien Didelot <vivien.didelot@...il.com>,
        netdev@...r.kernel.org, john@...ozen.org,
        linux-mediatek@...ts.infradead.org, linux-mips@...r.kernel.org
Subject: Re: [PATCH net-next 0/2] net: mediatek: Add MT7621 TRGMII mode
 support



On 6/17/2019 6:53 PM, Andrew Lunn wrote:
>> By adding some extra speed states in the code it seems to work.
>>
>> +               if (state->speed == 1200)
>> +                       mcr |= PMCR_FORCE_SPEED_1000;
> 
> Hi René
> 
> Is TRGMII always 1.2G? Or can you set it to 1000 or 1200? This
> PMCR_FORCE_SPEED_1000 feels wrong.

It is not uncommon to have to "force" 1G to get a higher speed, there is
something similar with B53 switches configuring the CPU ports at 2GB/sec
(proprietary too and not standardized either).

> 
>>> We could consider adding 1200BaseT/Full?
>>
>> I don't have any opinion about this.
>> It is great that it shows nicely in ethtool but I think supporting more
>> speeds in phy_speed_to_str() is enough.
>>
>> Also you may want to add other SOCs trgmii ranges too:
>> - 1200BaseT/Full for mt7621 only
>> - 2000BaseT/Full for mt7623 and mt7683
>> - 2600BaseT/Full for mt7623 only
> 
> Are these standardised in any way? Or MTK proprietary?  Also, is the T
> in BaseT correct? These speeds work over copper cables? Or should we
> be talking about 1200BaseKX?

Looks like this is MTK proprietary:

http://lists.infradead.org/pipermail/linux-mediatek/2016-September/007083.html
https://patchwork.kernel.org/patch/9341129/
-- 
Florian