netdev - Re: [PATCH v5 net-next] net: ftmac100: support mtu

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Date:   Thu, 27 Oct 2022 14:35:13 +0300
From:   Vladimir Oltean <olteanv@...il.com>
To:     Sergei Antonov <saproj@...il.com>
Cc:     netdev@...r.kernel.org, andrew@...n.ch, pabeni@...hat.com,
        kuba@...nel.org, edumazet@...gle.com, davem@...emloft.net
Subject: Re: [PATCH v5 net-next] net: ftmac100: support mtu > 1500

Hi Sergei,

On Mon, Oct 24, 2022 at 08:58:23PM +0300, Sergei Antonov wrote:
> The ftmac100 controller considers packets >1518 (1500 + Ethernet + FCS)
> FTL (frame too long) and drops them. That is fine with mtu 1500 or less
> and it saves CPU time. When DSA is present, mtu is bigger (for VLAN
> tagging) and the controller's built-in behavior is not desired then. We
> can make the controller deliver FTL packets to the driver by setting
> FTMAC100_MACCR_RX_FTL. Then we have to check ftmac100_rxdes_frame_length()
> (packet length sans FCS) on packets marked with FTMAC100_RXDES0_FTL flag.
> 
> Check for mtu > 1500 in .ndo_open() and set FTMAC100_MACCR_RX_FTL to let
> the driver FTL packets. Implement .ndo_change_mtu() and check for
> mtu > 1500 to set/clear FTMAC100_MACCR_RX_FTL dynamically.
> 
> Fixes: 8d77c036b57c ("net: add Faraday FTMAC100 10/100 Ethernet driver")
> Signed-off-by: Sergei Antonov <saproj@...il.com>
> ---

I think it's clear there are problems in communication between us, so
let me try differently.

Does the attached series of 3 patches work for you? I only compile
tested them.

I tried to keep as much of your work and authorship as possible, the
intention was to rewrite the justification in the commit message and to
fix the things which your patches didn't do (as separate patches).

View attachment "0001-net-ftmac100-prepare-data-path-for-receiving-single-.patch" of type "text/x-diff" (2714 bytes)

View attachment "0002-net-ftmac100-report-the-correct-maximum-MTU-of-1500.patch" of type "text/x-diff" (1984 bytes)

View attachment "0003-net-ftmac100-allow-increasing-MTU-to-make-most-use-o.patch" of type "text/x-diff" (4285 bytes)