1// SPDX-License-Identifier: GPL-2.0
  2/* Copyright (c) 2019, Vladimir Oltean <olteanv@gmail.com>
  3 */
  4#include <linux/if_vlan.h>
  5#include <linux/dsa/sja1105.h>
  6#include <linux/dsa/8021q.h>
  7#include <linux/packing.h>
  8#include "dsa_priv.h"
  9
 10/* Similar to is_link_local_ether_addr(hdr->h_dest) but also covers PTP */
 11static inline bool sja1105_is_link_local(const struct sk_buff *skb)
 12{
 13	const struct ethhdr *hdr = eth_hdr(skb);
 14	u64 dmac = ether_addr_to_u64(hdr->h_dest);
 15
 16	if (ntohs(hdr->h_proto) == ETH_P_SJA1105_META)
 17		return false;
 18	if ((dmac & SJA1105_LINKLOCAL_FILTER_A_MASK) ==
 19		    SJA1105_LINKLOCAL_FILTER_A)
 20		return true;
 21	if ((dmac & SJA1105_LINKLOCAL_FILTER_B_MASK) ==
 22		    SJA1105_LINKLOCAL_FILTER_B)
 23		return true;
 24	return false;
 25}
 26
 27struct sja1105_meta {
 28	u64 tstamp;
 29	u64 dmac_byte_4;
 30	u64 dmac_byte_3;
 31	u64 source_port;
 32	u64 switch_id;
 33};
 34
 35static void sja1105_meta_unpack(const struct sk_buff *skb,
 36				struct sja1105_meta *meta)
 37{
 38	u8 *buf = skb_mac_header(skb) + ETH_HLEN;
 39
 40	/* UM10944.pdf section 4.2.17 AVB Parameters:
 41	 * Structure of the meta-data follow-up frame.
 42	 * It is in network byte order, so there are no quirks
 43	 * while unpacking the meta frame.
 44	 *
 45	 * Also SJA1105 E/T only populates bits 23:0 of the timestamp
 46	 * whereas P/Q/R/S does 32 bits. Since the structure is the
 47	 * same and the E/T puts zeroes in the high-order byte, use
 48	 * a unified unpacking command for both device series.
 49	 */
 50	packing(buf,     &meta->tstamp,     31, 0, 4, UNPACK, 0);
 51	packing(buf + 4, &meta->dmac_byte_4, 7, 0, 1, UNPACK, 0);
 52	packing(buf + 5, &meta->dmac_byte_3, 7, 0, 1, UNPACK, 0);
 53	packing(buf + 6, &meta->source_port, 7, 0, 1, UNPACK, 0);
 54	packing(buf + 7, &meta->switch_id,   7, 0, 1, UNPACK, 0);
 55}
 56
 57static inline bool sja1105_is_meta_frame(const struct sk_buff *skb)
 58{
 59	const struct ethhdr *hdr = eth_hdr(skb);
 60	u64 smac = ether_addr_to_u64(hdr->h_source);
 61	u64 dmac = ether_addr_to_u64(hdr->h_dest);
 62
 63	if (smac != SJA1105_META_SMAC)
 64		return false;
 65	if (dmac != SJA1105_META_DMAC)
 66		return false;
 67	if (ntohs(hdr->h_proto) != ETH_P_SJA1105_META)
 68		return false;
 69	return true;
 70}
 71
 72/* This is the first time the tagger sees the frame on RX.
 73 * Figure out if we can decode it.
 74 */
 75static bool sja1105_filter(const struct sk_buff *skb, struct net_device *dev)
 76{
 77	if (!dsa_port_is_vlan_filtering(dev->dsa_ptr))
 78		return true;
 79	if (sja1105_is_link_local(skb))
 80		return true;
 81	if (sja1105_is_meta_frame(skb))
 82		return true;
 83	return false;
 84}
 85
 86static struct sk_buff *sja1105_xmit(struct sk_buff *skb,
 87				    struct net_device *netdev)
 88{
 89	struct dsa_port *dp = dsa_slave_to_port(netdev);
 90	struct dsa_switch *ds = dp->ds;
 91	u16 tx_vid = dsa_8021q_tx_vid(ds, dp->index);
 92	u16 queue_mapping = skb_get_queue_mapping(skb);
 93	u8 pcp = netdev_txq_to_tc(netdev, queue_mapping);
 94
 95	/* Transmitting management traffic does not rely upon switch tagging,
 96	 * but instead SPI-installed management routes. Part 2 of this
 97	 * is the .port_deferred_xmit driver callback.
 98	 */
 99	if (unlikely(sja1105_is_link_local(skb)))
100		return dsa_defer_xmit(skb, netdev);
101
102	/* If we are under a vlan_filtering bridge, IP termination on
103	 * switch ports based on 802.1Q tags is simply too brittle to
104	 * be passable. So just defer to the dsa_slave_notag_xmit
105	 * implementation.
106	 */
107	if (dsa_port_is_vlan_filtering(dp))
108		return skb;
109
110	return dsa_8021q_xmit(skb, netdev, ETH_P_SJA1105,
111			     ((pcp << VLAN_PRIO_SHIFT) | tx_vid));
112}
113
114static void sja1105_transfer_meta(struct sk_buff *skb,
115				  const struct sja1105_meta *meta)
116{
117	struct ethhdr *hdr = eth_hdr(skb);
118
119	hdr->h_dest[3] = meta->dmac_byte_3;
120	hdr->h_dest[4] = meta->dmac_byte_4;
121	SJA1105_SKB_CB(skb)->meta_tstamp = meta->tstamp;
122}
123
124/* This is a simple state machine which follows the hardware mechanism of
125 * generating RX timestamps:
126 *
127 * After each timestampable skb (all traffic for which send_meta1 and
128 * send_meta0 is true, aka all MAC-filtered link-local traffic) a meta frame
129 * containing a partial timestamp is immediately generated by the switch and
130 * sent as a follow-up to the link-local frame on the CPU port.
131 *
132 * The meta frames have no unique identifier (such as sequence number) by which
133 * one may pair them to the correct timestampable frame.
134 * Instead, the switch has internal logic that ensures no frames are sent on
135 * the CPU port between a link-local timestampable frame and its corresponding
136 * meta follow-up. It also ensures strict ordering between ports (lower ports
137 * have higher priority towards the CPU port). For this reason, a per-port
138 * data structure is not needed/desirable.
139 *
140 * This function pairs the link-local frame with its partial timestamp from the
141 * meta follow-up frame. The full timestamp will be reconstructed later in a
142 * work queue.
143 */
144static struct sk_buff
145*sja1105_rcv_meta_state_machine(struct sk_buff *skb,
146				struct sja1105_meta *meta,
147				bool is_link_local,
148				bool is_meta)
149{
150	struct sja1105_port *sp;
151	struct dsa_port *dp;
152
153	dp = dsa_slave_to_port(skb->dev);
154	sp = dp->priv;
155
156	/* Step 1: A timestampable frame was received.
157	 * Buffer it until we get its meta frame.
158	 */
159	if (is_link_local) {
160		if (!test_bit(SJA1105_HWTS_RX_EN, &sp->data->state))
161			/* Do normal processing. */
162			return skb;
163
164		spin_lock(&sp->data->meta_lock);
165		/* Was this a link-local frame instead of the meta
166		 * that we were expecting?
167		 */
168		if (sp->data->stampable_skb) {
169			dev_err_ratelimited(dp->ds->dev,
170					    "Expected meta frame, is %12llx "
171					    "in the DSA master multicast filter?\n",
172					    SJA1105_META_DMAC);
173			kfree_skb(sp->data->stampable_skb);
174		}
175
176		/* Hold a reference to avoid dsa_switch_rcv
177		 * from freeing the skb.
178		 */
179		sp->data->stampable_skb = skb_get(skb);
180		spin_unlock(&sp->data->meta_lock);
181
182		/* Tell DSA we got nothing */
183		return NULL;
184
185	/* Step 2: The meta frame arrived.
186	 * Time to take the stampable skb out of the closet, annotate it
187	 * with the partial timestamp, and pretend that we received it
188	 * just now (basically masquerade the buffered frame as the meta
189	 * frame, which serves no further purpose).
190	 */
191	} else if (is_meta) {
192		struct sk_buff *stampable_skb;
193
194		/* Drop the meta frame if we're not in the right state
195		 * to process it.
196		 */
197		if (!test_bit(SJA1105_HWTS_RX_EN, &sp->data->state))
198			return NULL;
199
200		spin_lock(&sp->data->meta_lock);
201
202		stampable_skb = sp->data->stampable_skb;
203		sp->data->stampable_skb = NULL;
204
205		/* Was this a meta frame instead of the link-local
206		 * that we were expecting?
207		 */
208		if (!stampable_skb) {
209			dev_err_ratelimited(dp->ds->dev,
210					    "Unexpected meta frame\n");
211			spin_unlock(&sp->data->meta_lock);
212			return NULL;
213		}
214
215		if (stampable_skb->dev != skb->dev) {
216			dev_err_ratelimited(dp->ds->dev,
217					    "Meta frame on wrong port\n");
218			spin_unlock(&sp->data->meta_lock);
219			return NULL;
220		}
221
222		/* Free the meta frame and give DSA the buffered stampable_skb
223		 * for further processing up the network stack.
224		 */
225		kfree_skb(skb);
226		skb = stampable_skb;
227		sja1105_transfer_meta(skb, meta);
228
229		spin_unlock(&sp->data->meta_lock);
230	}
231
232	return skb;
233}
234
235static struct sk_buff *sja1105_rcv(struct sk_buff *skb,
236				   struct net_device *netdev,
237				   struct packet_type *pt)
238{
239	struct sja1105_meta meta = {0};
240	int source_port, switch_id;
241	struct vlan_ethhdr *hdr;
242	u16 tpid, vid, tci;
243	bool is_link_local;
244	bool is_tagged;
245	bool is_meta;
246
247	hdr = vlan_eth_hdr(skb);
248	tpid = ntohs(hdr->h_vlan_proto);
249	is_tagged = (tpid == ETH_P_SJA1105);
250	is_link_local = sja1105_is_link_local(skb);
251	is_meta = sja1105_is_meta_frame(skb);
252
253	skb->offload_fwd_mark = 1;
254
255	if (is_tagged) {
256		/* Normal traffic path. */
257		tci = ntohs(hdr->h_vlan_TCI);
258		vid = tci & VLAN_VID_MASK;
259		source_port = dsa_8021q_rx_source_port(vid);
260		switch_id = dsa_8021q_rx_switch_id(vid);
261		skb->priority = (tci & VLAN_PRIO_MASK) >> VLAN_PRIO_SHIFT;
262	} else if (is_link_local) {
263		/* Management traffic path. Switch embeds the switch ID and
264		 * port ID into bytes of the destination MAC, courtesy of
265		 * the incl_srcpt options.
266		 */
267		source_port = hdr->h_dest[3];
268		switch_id = hdr->h_dest[4];
269		/* Clear the DMAC bytes that were mangled by the switch */
270		hdr->h_dest[3] = 0;
271		hdr->h_dest[4] = 0;
272	} else if (is_meta) {
273		sja1105_meta_unpack(skb, &meta);
274		source_port = meta.source_port;
275		switch_id = meta.switch_id;
276	} else {
277		return NULL;
278	}
279
280	skb->dev = dsa_master_find_slave(netdev, switch_id, source_port);
281	if (!skb->dev) {
282		netdev_warn(netdev, "Couldn't decode source port\n");
283		return NULL;
284	}
285
286	/* Delete/overwrite fake VLAN header, DSA expects to not find
287	 * it there, see dsa_switch_rcv: skb_push(skb, ETH_HLEN).
288	 */
289	if (is_tagged)
290		skb = dsa_8021q_remove_header(skb);
291
292	return sja1105_rcv_meta_state_machine(skb, &meta, is_link_local,
293					      is_meta);
294}
295
296static struct dsa_device_ops sja1105_netdev_ops = {
297	.name = "sja1105",
298	.proto = DSA_TAG_PROTO_SJA1105,
299	.xmit = sja1105_xmit,
300	.rcv = sja1105_rcv,
301	.filter = sja1105_filter,
302	.overhead = VLAN_HLEN,
303};
304
305MODULE_LICENSE("GPL v2");
306MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_SJA1105);
307
308module_dsa_tag_driver(sja1105_netdev_ops);