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Date: Wed, 4 May 2022 19:00:39 +0300
From: Vladimir Oltean <olteanv@...il.com>
To: Clément Léger <clement.leger@...tlin.com>
Cc: Andrew Lunn <andrew@...n.ch>,
Vivien Didelot <vivien.didelot@...il.com>,
Florian Fainelli <f.fainelli@...il.com>,
"David S . Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>,
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@...r.kernel.org, devicetree@...r.kernel.org,
linux-renesas-soc@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH net-next v3 02/12] net: dsa: add Renesas RZ/N1 switch tag
driver
On Wed, May 04, 2022 at 11:29:50AM +0200, Clément Léger wrote:
> The switch that is present on the Renesas RZ/N1 SoC uses a specific
> VLAN value followed by 6 bytes which contains forwarding configuration.
>
> Signed-off-by: Clément Léger <clement.leger@...tlin.com>
> ---
> include/net/dsa.h | 2 +
> net/dsa/Kconfig | 7 +++
> net/dsa/Makefile | 1 +
> net/dsa/tag_rzn1_a5psw.c | 114 +++++++++++++++++++++++++++++++++++++++
> 4 files changed, 124 insertions(+)
> create mode 100644 net/dsa/tag_rzn1_a5psw.c
>
> diff --git a/include/net/dsa.h b/include/net/dsa.h
> index d9da32aacbf1..9aaaa7deb102 100644
> --- a/include/net/dsa.h
> +++ b/include/net/dsa.h
> @@ -53,6 +53,7 @@ struct phylink_link_state;
> #define DSA_TAG_PROTO_SJA1110_VALUE 23
> #define DSA_TAG_PROTO_RTL8_4_VALUE 24
> #define DSA_TAG_PROTO_RTL8_4T_VALUE 25
> +#define DSA_TAG_PROTO_RZN1_A5PSW_VALUE 26
>
> enum dsa_tag_protocol {
> DSA_TAG_PROTO_NONE = DSA_TAG_PROTO_NONE_VALUE,
> @@ -81,6 +82,7 @@ enum dsa_tag_protocol {
> DSA_TAG_PROTO_SJA1110 = DSA_TAG_PROTO_SJA1110_VALUE,
> DSA_TAG_PROTO_RTL8_4 = DSA_TAG_PROTO_RTL8_4_VALUE,
> DSA_TAG_PROTO_RTL8_4T = DSA_TAG_PROTO_RTL8_4T_VALUE,
> + DSA_TAG_PROTO_RZN1_A5PSW = DSA_TAG_PROTO_RZN1_A5PSW_VALUE,
> };
>
> struct dsa_switch;
> diff --git a/net/dsa/Kconfig b/net/dsa/Kconfig
> index 8cb87b5067ee..e22f33d7cf60 100644
> --- a/net/dsa/Kconfig
> +++ b/net/dsa/Kconfig
> @@ -132,6 +132,13 @@ config NET_DSA_TAG_RTL8_4
> Say Y or M if you want to enable support for tagging frames for Realtek
> switches with 8 byte protocol 4 tags, such as the Realtek RTL8365MB-VC.
>
> +config NET_DSA_TAG_RZN1_A5PSW
> + tristate "Tag driver for Renesas RZ/N1 A5PSW switch"
> + help
> + Say Y or M if you want to enable support for tagging frames for
> + Renesas RZ/N1 embedded switch that uses a 8 byte tag located after
"an" 8 byte tag
> + destination MAC address.
> +
> config NET_DSA_TAG_LAN9303
> tristate "Tag driver for SMSC/Microchip LAN9303 family of switches"
> help
> diff --git a/net/dsa/Makefile b/net/dsa/Makefile
> index 9f75820e7c98..af28c24ead18 100644
> --- a/net/dsa/Makefile
> +++ b/net/dsa/Makefile
> @@ -17,6 +17,7 @@ obj-$(CONFIG_NET_DSA_TAG_OCELOT_8021Q) += tag_ocelot_8021q.o
> obj-$(CONFIG_NET_DSA_TAG_QCA) += tag_qca.o
> obj-$(CONFIG_NET_DSA_TAG_RTL4_A) += tag_rtl4_a.o
> obj-$(CONFIG_NET_DSA_TAG_RTL8_4) += tag_rtl8_4.o
> +obj-$(CONFIG_NET_DSA_TAG_RZN1_A5PSW) += tag_rzn1_a5psw.o
> obj-$(CONFIG_NET_DSA_TAG_SJA1105) += tag_sja1105.o
> obj-$(CONFIG_NET_DSA_TAG_TRAILER) += tag_trailer.o
> obj-$(CONFIG_NET_DSA_TAG_XRS700X) += tag_xrs700x.o
> diff --git a/net/dsa/tag_rzn1_a5psw.c b/net/dsa/tag_rzn1_a5psw.c
> new file mode 100644
> index 000000000000..87177682eb54
> --- /dev/null
> +++ b/net/dsa/tag_rzn1_a5psw.c
> @@ -0,0 +1,114 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright (C) 2022 Schneider Electric
> + *
> + * Clément Léger <clement.leger@...tlin.com>
> + */
> +
> +#include <linux/bitfield.h>
> +#include <linux/etherdevice.h>
> +#include <net/dsa.h>
> +
> +#include "dsa_priv.h"
> +
> +/* To define the outgoing port and to discover the incoming port a TAG is
> + * inserted after Src MAC :
> + *
> + * Dest MAC Src MAC TAG Type
> + * ...| 1 2 3 4 5 6 | 1 2 3 4 5 6 | 1 2 3 4 5 6 7 8 | 1 2 |...
> + * |<--------------->|
> + *
> + * See struct a5psw_tag for layout
> + */
> +
> +#define A5PSW_TAG_VALUE 0xE001
Maybe an ETH_P_DSA_A5PSW definition in include/uapi/linux/if_ether.h
would be appropriate? I'm not sure.
> +#define A5PSW_TAG_LEN 8
> +#define A5PSW_CTRL_DATA_FORCE_FORWARD BIT(0)
> +/* This is both used for xmit tag and rcv tagging */
> +#define A5PSW_CTRL_DATA_PORT GENMASK(3, 0)
> +
> +struct a5psw_tag {
> + __be16 ctrl_tag;
> + __be16 ctrl_data;
> + __be16 ctrl_data2_hi;
> + __be16 ctrl_data2_lo;
> +};
> +
> +static struct sk_buff *a5psw_tag_xmit(struct sk_buff *skb, struct net_device *dev)
> +{
> + struct dsa_port *dp = dsa_slave_to_port(dev);
> + struct a5psw_tag *ptag;
> + u32 data2_val;
> +
> + BUILD_BUG_ON(sizeof(*ptag) != A5PSW_TAG_LEN);
> +
> + /* The Ethernet switch we are interfaced with needs packets to be at
> + * least 64 bytes (including FCS) otherwise they will be discarded when
> + * they enter the switch port logic. When tagging is enabled, we need
> + * to make sure that packets are at least 70 bytes (including FCS and
> + * tag).
> + */
> + if (__skb_put_padto(skb, ETH_ZLEN + ETH_FCS_LEN + A5PSW_TAG_LEN, false))
> + return NULL;
I'm confused by the inclusion of the FCS length in this calculation,
since the FCS space isn't present in the skb buffer as far as I know?
"64 bytes including FCS" means "60 bytes excluding FCS".
And ETH_ZLEN is 60...
And I'm also not sure how we got to the number 70? A5PSW_TAG_LEN is 8.
If we add it to 60 we get 68. If we add it to 64 we get 72?
> +
> + /* provide 'A5PSW_TAG_LEN' bytes additional space */
> + skb_push(skb, A5PSW_TAG_LEN);
> +
> + /* make room between MACs and Ether-Type to insert tag */
> + dsa_alloc_etype_header(skb, A5PSW_TAG_LEN);
> +
> + ptag = dsa_etype_header_pos_tx(skb);
> +
> + data2_val = FIELD_PREP(A5PSW_CTRL_DATA_PORT, BIT(dp->index));
> + ptag->ctrl_tag = htons(A5PSW_TAG_VALUE);
> + ptag->ctrl_data = htons(A5PSW_CTRL_DATA_FORCE_FORWARD);
> + ptag->ctrl_data2_lo = htons(data2_val);
> + ptag->ctrl_data2_hi = 0;
> +
> + return skb;
> +}
> +
> +static struct sk_buff *a5psw_tag_rcv(struct sk_buff *skb,
> + struct net_device *dev)
> +{
> + struct a5psw_tag *tag;
> + int port;
> +
> + if (unlikely(!pskb_may_pull(skb, A5PSW_TAG_LEN))) {
> + dev_warn_ratelimited(&dev->dev,
> + "Dropping packet, cannot pull\n");
> + return NULL;
> + }
> +
> + tag = dsa_etype_header_pos_rx(skb);
> +
> + if (tag->ctrl_tag != htons(A5PSW_TAG_VALUE)) {
> + dev_warn_ratelimited(&dev->dev, "Dropping packet due to invalid TAG marker\n");
> + return NULL;
> + }
> +
> + port = FIELD_GET(A5PSW_CTRL_DATA_PORT, ntohs(tag->ctrl_data));
> +
> + skb->dev = dsa_master_find_slave(dev, 0, port);
> + if (!skb->dev)
> + return NULL;
> +
> + skb_pull_rcsum(skb, A5PSW_TAG_LEN);
> + dsa_strip_etype_header(skb, A5PSW_TAG_LEN);
> +
> + dsa_default_offload_fwd_mark(skb);
> +
> + return skb;
> +}
> +
> +static const struct dsa_device_ops a5psw_netdev_ops = {
> + .name = "a5psw",
> + .proto = DSA_TAG_PROTO_RZN1_A5PSW,
> + .xmit = a5psw_tag_xmit,
> + .rcv = a5psw_tag_rcv,
> + .needed_headroom = A5PSW_TAG_LEN,
> +};
> +
> +MODULE_LICENSE("GPL v2");
> +MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_A5PSW);
> +module_dsa_tag_driver(a5psw_netdev_ops);
> --
> 2.34.1
>
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