linux-kernel - Re: [PATCH net v2] net: dsa: realtek: rtl8365mb: fix GMII caps for ports with internal PHY

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Date:   Tue, 7 Jun 2022 19:52:25 +0100
From:   "Russell King (Oracle)" <linux@...linux.org.uk>
To:     Alvin Šipraga <alvin@...s.dk>
Cc:     luizluca@...il.com, Linus Walleij <linus.walleij@...aro.org>,
        Alvin Šipraga <alsi@...g-olufsen.dk>,
        Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Vladimir Oltean <olteanv@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH net v2] net: dsa: realtek: rtl8365mb: fix GMII caps for
 ports with internal PHY

On Tue, Jun 07, 2022 at 08:46:24PM +0200, Alvin Šipraga wrote:
> From: Alvin Šipraga <alsi@...g-olufsen.dk>
> 
> Since commit a18e6521a7d9 ("net: phylink: handle NA interface mode in
> phylink_fwnode_phy_connect()"), phylib defaults to GMII when no phy-mode
> or phy-connection-type property is specified in a DSA port node of the
> device tree. The same commit caused a regression in rtl8365mb whereby
> phylink would fail to connect, because the driver did not advertise
> support for GMII for ports with internal PHY.
> 
> It should be noted that the aforementioned regression is not because the
> blamed commit was incorrect: on the contrary, the blamed commit is
> correcting the previous behaviour whereby unspecified phy-mode would
> cause the internal interface mode to be PHY_INTERFACE_MODE_NA. The
> rtl8365mb driver only worked by accident before because it _did_
> advertise support for PHY_INTERFACE_MODE_NA, despite NA being reserved
> for internal use by phylink. With one mistake fixed, the other was
> exposed.
> 
> Commit a5dba0f207e5 ("net: dsa: rtl8365mb: add GMII as user port mode")
> then introduced implicit support for GMII mode on ports with internal
> PHY to allow a PHY connection for device trees where the phy-mode is not
> explicitly set to "internal". At this point everything was working OK
> again.
> 
> Subsequently, commit 6ff6064605e9 ("net: dsa: realtek: convert to
> phylink_generic_validate()") broke this behaviour again by discarding
> the usage of rtl8365mb_phy_mode_supported() - where this GMII support
> was indicated - while switching to the new .phylink_get_caps API.
> 
> With the new API, rtl8365mb_phy_mode_supported() is no longer needed.
> Remove it altogether and add back the GMII capability - this time to
> rtl8365mb_phylink_get_caps() - so that the above default behaviour works
> for ports with internal PHY again.
> 
> Fixes: 6ff6064605e9 ("net: dsa: realtek: convert to phylink_generic_validate()")
> Signed-off-by: Alvin Šipraga <alsi@...g-olufsen.dk>

Even though I raised concerns about the ext_int thing previously, this
is still a step forward, so:

Reviewed-by: Russell King (Oracle) <rmk+kernel@...linux.org.uk>

Thanks!

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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