netdev - Re: [RFC PATCH 0/3] net: macb: Wake-on-Lan magic packet fixes

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Message-ID: <CAFcVECLkPxN0nk=jr9AxJoV3i1jHBoY4s3yeodHDO2uOZspQPg@mail.gmail.com>
Date:   Fri, 3 Apr 2020 19:06:28 +0530
From:   Harini Katakam <harinik@...inx.com>
To:     Nicolas Ferre <nicolas.ferre@...rochip.com>
Cc:     linux-arm-kernel@...ts.infradead.org, netdev@...r.kernel.org,
        Claudiu Beznea <claudiu.beznea@...rochip.com>,
        Harini Katakam <harini.katakam@...inx.com>,
        linux-kernel@...r.kernel.org,
        "David S. Miller" <davem@...emloft.net>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Rafal Ozieblo <rafalo@...ence.com>,
        sergio.prado@...abworks.com, antoine.tenart@...tlin.com,
        Florian Fainelli <f.fainelli@...il.com>, linux@...linux.org.uk,
        Andrew Lunn <andrew@...n.ch>,
        Michal Simek <michal.simek@...inx.com>
Subject: Re: [RFC PATCH 0/3] net: macb: Wake-on-Lan magic packet fixes

Hi Nicolas,

On Fri, Apr 3, 2020 at 6:45 PM <nicolas.ferre@...rochip.com> wrote:
>
> From: Nicolas Ferre <nicolas.ferre@...rochip.com>
>
> Hi,
> Here are some of my early patches in order to fix WoL magic-packet on the
> current macb driver.
> Addition of this feature to GEM types of IPs is yet to come. I would like to
> have your feedback on these little patches first so that I can continue
> investigating the addition of GEM WoL magic-packet.
>
> Harini, I know that you have patches for GEM in order to integrate WoL ARP
> mode [1]. I'll try to integrate some of your work but would need that this feature
> is better integrated in current code. For instance, the choice of "magic
> packet" or "ARP" should be done by ethtool options and DT properties. For
> matching with mainline users, MACB and GEM code must co-exist.

Agree. I'll try to test this series and get back to you next week.

> The use of dumb buffers for RX seems also fairly platform specific and we would
> need to think more about it.

I know that the IP versions from r1p10 have a mechanism to disable DMA queues
(bit 0 of the queue pointer register) which is cleaner. But for
earlier IP versions,
I remember discussing with Cadence and there is no way to keep RX
enabled for WOL
with RX DMA disabled. I'm afraid that means there should be a bare
minimum memory
region with a dummy descriptor if you do not want to process the
packets. That memory
should also be accessible while the rest of the system is powered
down. Please let me
know if you think of any other solution.

Regards,
Harini