netdev - Re: [PATCH net-next] net: dsa: tag_rtl4_a: Drop bit 9 from egress frames

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Date:   Fri, 24 Sep 2021 01:12:00 +0300
From:   Vladimir Oltean <olteanv@...il.com>
To:     Linus Walleij <linus.walleij@...aro.org>
Cc:     DENG Qingfang <dqfext@...il.com>, Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next] net: dsa: tag_rtl4_a: Drop bit 9 from egress
 frames

On Thu, Sep 23, 2021 at 11:59:36PM +0200, Linus Walleij wrote:
> On Wed, Sep 15, 2021 at 9:20 AM DENG Qingfang <dqfext@...il.com> wrote:
> > On Mon, Sep 13, 2021 at 04:31:56PM +0200, Linus Walleij wrote:
> 
> > > This drops the code setting bit 9 on egress frames on the
> > > Realtek "type A" (RTL8366RB) frames.
> >
> > FYI, on RTL8366S, bit 9 on egress frames is disable learning.
> >
> > > This bit was set on ingress frames for unknown reason,
> >
> > I think it could be the reason why the frame is forwarded to the CPU.
> 
> Hm I suspect it disable learning on RTL8366RB as well.

Suspicion based on what?

> Do we have some use for that feature in DSA taggers?

Yes.