Re: [PATCH net-next 02/12] net: dsa: add Renesas RZ/N1 switch tag driver

Vladimir Oltean
2022-04-14T15:09:14Z

On Thu, Apr 14, 2022 at 02:22:40PM +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@bootlin.com>
> ---
> net/dsa/Kconfig | 8 +++
> net/dsa/Makefile | 1 +
> net/dsa/tag_rzn1_a5psw.c | 112 +++++++++++++++++++++++++++++++++++++++
> 3 files changed, 121 insertions(+)
> create mode 100644 net/dsa/tag_rzn1_a5psw.c
>
> diff --git a/net/dsa/Kconfig b/net/dsa/Kconfig
> index 8cb87b5067ee..e5b17108fa22 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
> + destination MAC address.
> +
> config NET_DSA_TAG_LAN9303
> tristate "Tag driver for SMSC/Microchip LAN9303 family of switches"
> help
> @@ -159,4 +166,5 @@ config NET_DSA_TAG_XRS700X
> Say Y or M if you want to enable support for tagging frames for
> Arrow SpeedChips XRS700x switches that use a single byte tag trailer.
>
> +

Stray change.

> endif
> 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..7818c1c0fca2
> --- /dev/null
> +++ b/net/dsa/tag_rzn1_a5psw.c
> @@ -0,0 +1,112 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright (C) 2022 Schneider Electric
> + *
> + * Clément Léger <clement.leger@bootlin.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
> +#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 {

This needs to be packed.

> + u16 ctrl_tag;
> + u16 ctrl_data;

These need to be __be16.

> + u32 ctrl_data2;

This needs to be __be32.

> +};
> +
> +static struct sk_buff *a5psw_tag_xmit(struct sk_buff *skb, struct net_device *dev)
> +{
> + struct a5psw_tag *ptag, tag = {0};
> + struct dsa_port *dp = dsa_slave_to_port(dev);

Please keep variable declarations sorted in decreasing order of line
length (applies throughout the patch series, I won't repeat this comment).

> + u32 data2_val;
> +
> + /* 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 68 bytes (including FCS and
> + * tag).
> + */
> + if (__skb_put_padto(skb, ETH_ZLEN + sizeof(tag), false))
> + return NULL;
> +
> + /* 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));
> + tag.ctrl_tag = htons(A5PSW_TAG_VALUE);
> + tag.ctrl_data = htons(A5PSW_CTRL_DATA_FORCE_FORWARD);
> + tag.ctrl_data2 = htonl(data2_val);
> +
> + memcpy(ptag, &tag, sizeof(struct a5psw_tag));

sizeof(tag), to be consistent with the other use of sizeof() above?
Although, hmm, I think you could get away with editing "ptag" in place.

> +
> + 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
>