netdev - Re: [net-next v2 00/12] add support for Renesas RZ/N1 ethernet subsystem devices

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Date:   Mon, 2 May 2022 14:27:38 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Clément Léger <clement.leger@...tlin.com>
Cc:     Jakub Kicinski <kuba@...nel.org>, 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>,
        Paolo Abeni <pabeni@...hat.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Magnus Damm <magnus.damm@...il.com>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        Herve Codina <herve.codina@...tlin.com>,
        Miquèl Raynal <miquel.raynal@...tlin.com>,
        Milan Stevanovic <milan.stevanovic@...com>,
        Jimmy Lalande <jimmy.lalande@...com>,
        Pascal Eberhard <pascal.eberhard@...com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
        netdev <netdev@...r.kernel.org>
Subject: Re: [net-next v2 00/12] add support for Renesas RZ/N1 ethernet
 subsystem devices

Hi Clément,

On Mon, May 2, 2022 at 8:52 AM Clément Léger <clement.leger@...tlin.com> wrote:
> Le Fri, 29 Apr 2022 12:32:35 -0700,
> Jakub Kicinski <kuba@...nel.org> a écrit :
>
> > On Fri, 29 Apr 2022 16:34:53 +0200 Clément Léger wrote:
> > > The Renesas RZ/N1 SoCs features an ethernet subsystem which contains
> > > (most notably) a switch, two GMACs, and a MII converter [1]. This
> > > series adds support for the switch and the MII converter.
> > >
> > > The MII converter present on this SoC has been represented as a PCS
> > > which sit between the MACs and the PHY. This PCS driver is probed from
> > > the device-tree since it requires to be configured. Indeed the MII
> > > converter also contains the registers that are handling the muxing of
> > > ports (Switch, MAC, HSR, RTOS, etc) internally to the SoC.
> > >
> > > The switch driver is based on DSA and exposes 4 ports + 1 CPU
> > > management port. It include basic bridging support as well as FDB and
> > > statistics support.
> >
> > Build's not happy (W=1 C=1):
> >
> > drivers/net/dsa/rzn1_a5psw.c:574:29: warning: symbol 'a5psw_switch_ops' was not declared. Should it be static?
> > In file included from ../drivers/net/dsa/rzn1_a5psw.c:17:
> > drivers/net/dsa/rzn1_a5psw.h:221:1: note: offset of packed bit-field ‘port_mask’ has changed in GCC 4.4
> >   221 | } __packed;
> >       | ^
> >
>
> Hi Jakub, I only had this one (due to the lack of W=1 C=1 I guess) which
> I thought (wrongly) that it was due to my GCC version:
>
>   CC      net/dsa/switch.o
>   CC      net/dsa/tag_8021q.o
> In file included from ../drivers/net/dsa/rzn1_a5psw.c:17:
> ../drivers/net/dsa/rzn1_a5psw.h:221:1: note: offset of packed bit-field
>   ‘port_mask’ has changed in GCC 4.4 221 | } __packed;
>       | ^
>   CC      kernel/module.o
>   CC      drivers/net/ethernet/stmicro/stmmac/dwmac1000_core.o
>   CC      drivers/net/ethernet/stmicro/stmmac/dwmac100_core.o
>
> I'll fix the other errors which are more trivial, however, I did not
> found a way to fix the packed bit-field warning.

The "port_mask" field is split across 2 u8s.
What about using u16 instead, and adding explicit padding while
at it? The below gets rid of the warning, while the generated code
is the same.

--- a/drivers/net/dsa/rzn1_a5psw.h
+++ b/drivers/net/dsa/rzn1_a5psw.h
@@ -169,10 +169,11 @@

 struct fdb_entry {
        u8 mac[ETH_ALEN];
-       u8 valid:1;
-       u8 is_static:1;
-       u8 prio:3;
-       u8 port_mask:5;
+       u16 valid:1;
+       u16 is_static:1;
+       u16 prio:3;
+       u16 port_mask:5;
+       u16 reserved:6;
 } __packed;

 union lk_data {

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds