netdev - RE: FEC on i.MX 7 transmit queue timeout

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Date:   Mon, 8 May 2017 02:13:25 +0000
From:   Andy Duan <fugang.duan@....com>
To:     Andrew Lunn <andrew@...n.ch>
CC:     Stefan Agner <stefan@...er.ch>,
        "festevam@...il.com" <festevam@...il.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "netdev-owner@...r.kernel.org" <netdev-owner@...r.kernel.org>
Subject: RE: FEC on i.MX 7 transmit queue timeout

From: Andrew Lunn <andrew@...n.ch> Sent: Friday, May 05, 2017 8:24 PM
>To: Andy Duan <fugang.duan@....com>
>Cc: Stefan Agner <stefan@...er.ch>; festevam@...il.com;
>netdev@...r.kernel.org; netdev-owner@...r.kernel.org
>Subject: Re: FEC on i.MX 7 transmit queue timeout
>
>> No, it is not workaround. As i said, quque1 and queue2 are for AVB
>> paths have higher priority in transmition.
>
>Does this higher priority result in the low priority queue being starved? Is that
>why the timer goes off? What happens when somebody does use AVB. Are
>we back to the same problem? This is what seems to make is sounds like a
>work around, not a fix.
>
>     Andrew
Yes, queue0 may be blocked by queue1 and queue2, then the queue0 watchdog time maybe triggered.
If somebody use AVB quque1 and queue2, the remaining bandwidth is for queue0, for example, in 100Mbps system, quque1 cost 50Mbps bandwidth and queue2 cost 50Mbps bandwidth for audio and video streaming, then queue0 (best effort) has 0 bandwidth that limit user case cannot have  asynchronous frames (IP(tcp/udp)) on networking. Of course these is extreme case. 
In essentially,  asynchronous frames (IP) go queue0 for the original design. To do these just implement .ndo_select_queue() callback in driver like fsl tree.

Regards,
Andy