netdev - Re: [RFC PATCH v1] net: ethernet: nb8800: Reset HW block in ndo

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Date:   Fri, 28 Jul 2017 18:43:42 +0200
From:   Marc Gonzalez <marc_gonzalez@...madesigns.com>
To:     Mans Rullgard <mans@...sr.com>
CC:     Florian Fainelli <f.fainelli@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        netdev <netdev@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Mason <slash.tmp@...e.fr>
Subject: Re: [RFC PATCH v1] net: ethernet: nb8800: Reset HW block in ndo_open

On 28/07/2017 18:17, Måns Rullgård wrote:

> Marc Gonzalez wrote:
> 
>> ndo_stop breaks RX in a way that ndo_open is unable to undo.
> 
> Please elaborate.  Why can't it be fixed in a less heavy-handed way?

I'm not sure what "elaborate" means. After we've been through
ndo_stop once, the board can send packets, but it doesn't see
any replies from remote systems. RX is wedged.

I think ndo_stop is rare enough an event that doing a full
reset is not an issue, in terms of performance. Also I will
need this infrastructure anyway for suspend/resume support.

It might also make sense to put the HW in reset at close
(to save power). I will try measuring the power savings,
if any.

>> Work around the issue by resetting the HW in ndo_open.
>> This will provide the basis for suspend/resume support.
>>
>> Signed-off-by: Marc Gonzalez <marc_gonzalez@...madesigns.com>
>> ---
>>  drivers/net/ethernet/aurora/nb8800.c | 40 +++++++++++++++++-------------------
>>  drivers/net/ethernet/aurora/nb8800.h |  1 +
>>  2 files changed, 20 insertions(+), 21 deletions(-)
> 
> I'm pretty sure this doesn't preserve everything it should.

Hmmm, we're supposed to start fresh ("full reset").
What could there be to preserve?
You mentioned flow control and multicast elsewhere.
I will take a closer look. Thanks for the heads up.

Regards.