linux-kernel - Re: [PATCH v2] net: dsa: mv88e6xxx: Fix port_hidden_wait to account for port_base

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Date:   Sun, 24 Apr 2022 21:33:59 +0200
From:   Marek Behún <kabel@...nel.org>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     Nathan Rossi <nathan@...hanrossi.com>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Vladimir Oltean <olteanv@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>
Subject: Re: [PATCH v2] net: dsa: mv88e6xxx: Fix port_hidden_wait to account
 for port_base_addr

On Sun, 24 Apr 2022 21:26:58 +0200
Andrew Lunn <andrew@...n.ch> wrote:

> On Sun, Apr 24, 2022 at 03:31:43PM +0000, Nathan Rossi wrote:
> > The other port_hidden functions rely on the port_read/port_write
> > functions to access the hidden control port. These functions apply the
> > offset for port_base_addr where applicable. Update port_hidden_wait to
> > use the port_wait_bit so that port_base_addr offsets are accounted for
> > when waiting for the busy bit to change.
> > 
> > Without the offset the port_hidden_wait function would timeout on
> > devices that have a non-zero port_base_addr (e.g. MV88E6141), however
> > devices that have a zero port_base_addr would operate correctly (e.g.
> > MV88E6390).
> > 
> > Fixes: ea89098ef9a5 ("net: dsa: mv88x6xxx: mv88e6390 errata")  
> 
> That is further back than needed. And due to the code moving around
> and getting renamed, you are added extra burden on those doing the
> back port for no actual gain.
> 
> Please verify what i suggested, 609070133aff1 is better and then
> repost.

The bug was introduced by ea89098ef9a5.
609070133aff1 is only requirement for this fix, but Fixes tag should reference
the commit which introduced the bug, afaik.

So it should be 

Fixes: ea89098ef9a5 ("net: dsa: mv88x6xxx: mv88e6390 errata")
Cc: stable@...r.kernel.org # 609070133aff ("net: dsa: mv88e6xxx: update code operating on hidden registers")

Marek