linux-kernel - Re: [PATCH 6/7] netdev: octeon-ethernet: Add Cavium Octeon III support.

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Date:   Thu, 2 Nov 2017 09:37:18 -0700
From:   David Daney <ddaney@...iumnetworks.com>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     David Daney <david.daney@...ium.com>, linux-mips@...ux-mips.org,
        ralf@...ux-mips.org, James Hogan <james.hogan@...s.com>,
        netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        linux-kernel@...r.kernel.org,
        "Steven J. Hill" <steven.hill@...ium.com>,
        devicetree@...r.kernel.org, Carlos Munoz <cmunoz@...ium.com>
Subject: Re: [PATCH 6/7] netdev: octeon-ethernet: Add Cavium Octeon III
 support.

On 11/02/2017 09:10 AM, Andrew Lunn wrote:
> On Thu, Nov 02, 2017 at 08:55:33AM -0700, David Daney wrote:
>> On 11/02/2017 05:43 AM, Andrew Lunn wrote:
>> [...]
>>>> +
>>>> +		i = atomic_inc_return(&pki_id);
>>>> +		pki_dev = platform_device_register_data(&new_dev->dev,
>>>> +							is_mix ? "octeon_mgmt" : "ethernet-mac-pki",
>>>> +							i, &platform_data, sizeof(platform_data));
>>>> +		dev_info(&pdev->dev, "Created %s %u: %p\n",
>>>> +			 is_mix ? "MIX" : "PKI", pki_dev->id, pki_dev);
>>>
>>> Is there any change of these ethernet ports being used to connect to
>>> an Ethernet switch. We have had issues in the past with these sort of
>>> platform devices combined with DSA.
>>>
>>
>> There are only two possibilities.  The BGX MACs have a multiplexer that
>> allows them to be connected to either the "octeon_mgmt" MIX packet
>> processor, or to the "ethernet-mac-pki" PKI/PKO packet processor.  The SoCs
>> supported by these drivers do not contain any hardware that would be
>> considered an "Ethernet switch".
> 
> Hi David
> 
> I was thinking of an external Ethernet switch. You generally connect
> via RGMII to a port of the switch.
> 

OK, now I think I understand.  Yes, the MAC can be hardwired to a 
switch.  In fact, there are system designs that do exactly that.

We try to handle this case by not having a "phy-handle" property in the 
device tree.  The link to the remote device (switch IC in this case) is 
brought up on ndo_open()

There may be opportunities to improve how this works in the future, but 
the current code is serviceable.

> http://elixir.free-electrons.com/linux/v4.9.60/source/Documentation/networking/dsa/dsa.txt
> 
> 	Andrew
>