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Message-ID: <c5f4e12beb6381c5ae08322f1316efcecf292e12.camel@microchip.com>
Date: Mon, 26 Apr 2021 10:03:52 +0530
From: Prasanna Vengateshan <prasanna.vengateshan@...rochip.com>
To: Vladimir Oltean <olteanv@...il.com>
CC: <andrew@...n.ch>, <netdev@...r.kernel.org>, <robh+dt@...nel.org>,
<UNGLinuxDriver@...rochip.com>, <hkallweit1@...il.com>,
<linux@...linux.org.uk>, <davem@...emloft.net>, <kuba@...nel.org>,
<linux-kernel@...r.kernel.org>, <vivien.didelot@...il.com>,
<f.fainelli@...il.com>, <devicetree@...r.kernel.org>
Subject: Re: [PATCH v2 net-next 3/9] net: dsa: tag_ksz: add tag handling for
Microchip LAN937x
On Thu, 2021-04-22 at 22:18 +0300, Vladimir Oltean wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the
> content is safe
>
> On Thu, Apr 22, 2021 at 03:12:51PM +0530, Prasanna Vengateshan wrote:
> > The Microchip LAN937X switches have a tagging protocol which is
> > very similar to KSZ tagging. So that the implementation is added to
> > tag_ksz.c and reused common APIs
> >
> > Signed-off-by: Prasanna Vengateshan <prasanna.vengateshan@...rochip.com>
> > ---
> > include/net/dsa.h | 2 ++
> > net/dsa/Kconfig | 4 ++--
> > net/dsa/tag_ksz.c | 58 +++++++++++++++++++++++++++++++++++++++++++++++
> > 3 files changed, 62 insertions(+), 2 deletions(-)
> >
> > diff --git a/include/net/dsa.h b/include/net/dsa.h
> > index 507082959aa4..98c1ab6dc4dc 100644
> > --- a/include/net/dsa.h
> > +++ b/include/net/dsa.h
> > @@ -50,6 +50,7 @@ struct phylink_link_state;
> > #define DSA_TAG_PROTO_OCELOT_8021Q_VALUE 20
> > #define DSA_TAG_PROTO_SEVILLE_VALUE 21
> > #define DSA_TAG_PROTO_BRCM_LEGACY_VALUE 22
> > +#define DSA_TAG_PROTO_LAN937X_VALUE 23
> >
> > enum dsa_tag_protocol {
> > DSA_TAG_PROTO_NONE = DSA_TAG_PROTO_NONE_VALUE,
> > @@ -75,6 +76,7 @@ enum dsa_tag_protocol {
> > DSA_TAG_PROTO_XRS700X = DSA_TAG_PROTO_XRS700X_VALUE,
> > DSA_TAG_PROTO_OCELOT_8021Q = DSA_TAG_PROTO_OCELOT_8021Q_VALUE,
> > DSA_TAG_PROTO_SEVILLE = DSA_TAG_PROTO_SEVILLE_VALUE,
> > + DSA_TAG_PROTO_LAN937X = DSA_TAG_PROTO_LAN937X_VALUE,
> > };
> >
> > struct packet_type;
> > diff --git a/net/dsa/Kconfig b/net/dsa/Kconfig
> > index cbc2bd643ab2..888eb79a85f2 100644
> > --- a/net/dsa/Kconfig
> > +++ b/net/dsa/Kconfig
> > @@ -97,10 +97,10 @@ config NET_DSA_TAG_MTK
> > Mediatek switches.
> >
> > config NET_DSA_TAG_KSZ
> > - tristate "Tag driver for Microchip 8795/9477/9893 families of
> > switches"
> > + tristate "Tag driver for Microchip 8795/937x/9477/9893 families of
> > switches"
> > help
> > Say Y if you want to enable support for tagging frames for the
> > - Microchip 8795/9477/9893 families of switches.
> > + Microchip 8795/937x/9477/9893 families of switches.
> >
> > config NET_DSA_TAG_RTL4_A
> > tristate "Tag driver for Realtek 4 byte protocol A tags"
> > diff --git a/net/dsa/tag_ksz.c b/net/dsa/tag_ksz.c
> > index 4820dbcedfa2..a67f21bdab8f 100644
> > --- a/net/dsa/tag_ksz.c
> > +++ b/net/dsa/tag_ksz.c
> > @@ -190,10 +190,68 @@ static const struct dsa_device_ops ksz9893_netdev_ops
> > = {
> > DSA_TAG_DRIVER(ksz9893_netdev_ops);
> > MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_KSZ9893);
> >
> > +/* For xmit, 2 bytes are added before FCS.
> > + * ------------------------------------------------------------------------
> > ---
> > + *
> > DA(6bytes)|SA(6bytes)|....|Data(nbytes)|tag0(1byte)|tag1(1byte)|FCS(4bytes)
> > + * ------------------------------------------------------------------------
> > ---
> > + * tag0 : represents tag override, lookup and valid
> > + * tag1 : each bit represents port (eg, 0x01=port1, 0x02=port2, 0x80=port8)
> > + *
> > + * For rcv, 1 byte is added before FCS.
> > + * ------------------------------------------------------------------------
> > ---
> > + * DA(6bytes)|SA(6bytes)|....|Data(nbytes)|tag0(1byte)|FCS(4bytes)
> > + * ------------------------------------------------------------------------
> > ---
> > + * tag0 : zero-based value represents port
> > + * (eg, 0x00=port1, 0x02=port3, 0x07=port8)
> > + */
> > +#define LAN937X_INGRESS_TAG_LEN 2
> > +
> > +#define LAN937X_TAIL_TAG_OVERRIDE BIT(11)
>
> I had to look up the datasheet, to see what this is, because "override"
> can mean many things, not all of them are desirable.
>
> Port Blocking Override
> When set, packets will be sent from the specified port(s) regardless, and any
> port
> blocking (see Port Transmit Enable in Port MSTP State Register) is ignored.
>
> Do you think you can name it LAN937X_TAIL_TAG_BLOCKING_OVERRIDE? I know
> it's longer, but it's also more suggestive.
Thanks for reviewing the patch series. Suggestion looks meaningful. Noted for
next rev.
>
> > +#define LAN937X_TAIL_TAG_LOOKUP BIT(12)
> > +#define LAN937X_TAIL_TAG_VALID BIT(13)
> > +#define LAN937X_TAIL_TAG_PORT_MASK 7
> > +
> > +static struct sk_buff *lan937x_xmit(struct sk_buff *skb,
> > + struct net_device *dev)
> > +{
> > + struct dsa_port *dp = dsa_slave_to_port(dev);
> > + __be16 *tag;
> > + u8 *addr;
> > + u16 val;
> > +r
> > + tag = skb_put(skb, LAN937X_INGRESS_TAG_LEN);
>
> Here we go again.. why is it called INGRESS_TAG_LEN if it is used during
> xmit, and only during xmit?
Definition is ingress to the LAN937x since it has different tag length for
ingress and egress of LAN937x. Do you think should it be changed?
>
> > + addr = skb_mac_header(skb);
>
> My personal choice would have been:
>
> const struct ethhdr *hdr = eth_hdr(skb);
>
> if (is_link_local_ether_addr(hdr->h_dest))
It makes more understandable since h_dest is passed. Noted.
>
> >
> > 2.27.0
> >
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