Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
MIME-Version: 1.0
References: <20201129102400.157786-1-jean.pihet@newoldbits.com>
 <20201129165627.GA2234159@lunn.ch> <CAORVsuUez9qteuuqkGpQbU5yXjAFxcpRXGaXnKwqm-hKSKF6NQ@mail.gmail.com>
 <20201129193822.GP2234159@lunn.ch>
In-Reply-To: <20201129193822.GP2234159@lunn.ch>
From:   Jean Pihet <jean.pihet@newoldbits.com>
Date:   Sun, 29 Nov 2020 20:48:25 +0100
Message-ID: <CAORVsuWKtdF8O9vXonamWEr0WcdoZiaeFhjP06Z8NV_wv3A=KQ@mail.gmail.com>
Subject: Re: [PATCH 1/2] net: dsa: ksz: pad frame to 64 bytes for transmission
To:     Andrew Lunn <andrew@lunn.ch>
Cc:     netdev@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>,
        Ryan Barnett <ryan.barnett@rockwellcollins.com>,
        Conrad Ratschan <conrad.ratschan@rockwellcollins.com>,
        Hugo Cornelis <hugo.cornelis@essensium.com>,
        Arnout Vandecappelle <arnout.vandecappelle@essensium.com>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

Andrew,

On Sun, Nov 29, 2020 at 8:38 PM Andrew Lunn <andrew@lunn.ch> wrote:
>
> On Sun, Nov 29, 2020 at 08:34:27PM +0100, Jean Pihet wrote:
> > Hi Andrew,
> >
> > On Sun, Nov 29, 2020 at 5:56 PM Andrew Lunn <andrew@lunn.ch> wrote:
> > >
> > > On Sun, Nov 29, 2020 at 11:23:59AM +0100, Jean Pihet wrote:
> > > > Some ethernet controllers (e.g. TI CPSW) pad the frames to a minimum
> > > > of 64 bytes before the FCS is appended. This causes an issue with the
> > > > KSZ tail tag which could not be the last byte before the FCS.
> > > > Solve this by padding the frame to 64 bytes minus the tail tag size,
> > > > before the tail tag is added and the frame is passed for transmission.
> > >
> > > Hi Jean
> > >
> > > what tree is this based on? Have you seen
> > The patches are based on the latest mainline v5.10-rc5. Is this the
> > recommended version to submit new patches?
>
> No, that is old. Please take a read of:
>
> https://www.kernel.org/doc/html/latest/networking/netdev-FAQ.html

Ok got it, thx!

Found the commit 88fda8ee and its parent [1] with the following
comment, which seems to indicate that my patch is not needed anymore.
Can you confirm?

/* For tail taggers, we need to pad short frames ourselves, to ensure
+ * that the tail tag does not fail at its role of being at the end of
+ * the packet, once the master interface pads the frame. Account for
+ * that pad length here, and pad later.
...

[1] https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net.git/commit/?id=a3b0b6479700a5b0af2c631cb2ec0fb7a0d978f2

Thx,
Jean

>
>         Andrew