Re: [PATCH 5/7] net: dsa: b53: Add logic for RX timestamping

From: Florian Fainelli
Date: Fri Nov 05 2021 - 22:36:19 EST



On 11/4/2021 6:31 AM, Martin Kaistra wrote:
Packets received by the tagger with opcode=1 contain the 32-bit timestamp
according to the timebase register. This timestamp is saved in
BRCM_SKB_CB(skb)->meta_tstamp. b53_port_rxtstamp() takes this
and puts the full time information from the timecounter into
shwt->hwtstamp.

Signed-off-by: Martin Kaistra <martin.kaistra@xxxxxxxxxxxxx>
---
drivers/net/dsa/b53/b53_common.c | 1 +
drivers/net/dsa/b53/b53_ptp.c | 28 ++++++++++++++++++++++++++
drivers/net/dsa/b53/b53_ptp.h | 10 ++++++++++
include/linux/dsa/b53.h | 30 ++++++++++++++++++++++++++++
net/dsa/tag_brcm.c | 34 ++++++++++++++++++++++----------
5 files changed, 93 insertions(+), 10 deletions(-)

diff --git a/drivers/net/dsa/b53/b53_common.c b/drivers/net/dsa/b53/b53_common.c
index ed590efbd3bf..a9408f9cd414 100644
--- a/drivers/net/dsa/b53/b53_common.c
+++ b/drivers/net/dsa/b53/b53_common.c
@@ -2300,6 +2300,7 @@ static const struct dsa_switch_ops b53_switch_ops = {
.port_max_mtu = b53_get_max_mtu,
.port_change_mtu = b53_change_mtu,
.get_ts_info = b53_get_ts_info,
+ .port_rxtstamp = b53_port_rxtstamp,
};
struct b53_chip_data {
diff --git a/drivers/net/dsa/b53/b53_ptp.c b/drivers/net/dsa/b53/b53_ptp.c
index 324335465232..86ebaa522084 100644
--- a/drivers/net/dsa/b53/b53_ptp.c
+++ b/drivers/net/dsa/b53/b53_ptp.c
@@ -6,6 +6,8 @@
* Copyright (C) 2021 Linutronix GmbH
*/
+#include <linux/ptp_classify.h>
+
#include "b53_priv.h"
#include "b53_ptp.h"
@@ -107,6 +109,32 @@ static void b53_ptp_overflow_check(struct work_struct *work)
schedule_delayed_work(&dev->overflow_work, B53_PTP_OVERFLOW_PERIOD);
}
+bool b53_port_rxtstamp(struct dsa_switch *ds, int port, struct sk_buff *skb,
+ unsigned int type)
+{
+ struct b53_device *dev = ds->priv;
+ struct b53_port_hwtstamp *ps = &dev->ports[port].port_hwtstamp;
+ struct skb_shared_hwtstamps *shwt;
+ u64 ns;
+
+ if (type != PTP_CLASS_V2_L2)
+ return false;
+
+ if (!test_bit(B53_HWTSTAMP_ENABLED, &ps->state))
+ return false;
+
+ mutex_lock(&dev->ptp_mutex);
+ ns = BRCM_SKB_CB(skb)->meta_tstamp;
+ ns = timecounter_cyc2time(&dev->tc, ns);

Why not fold this directly:

ns = timecoutner_cyc2time(&dev->tc, (u64)BRCM_SKB_CB(skb)->meta_stamp)

+ mutex_unlock(&dev->ptp_mutex);
+
+ shwt = skb_hwtstamps(skb);
+ memset(shwt, 0, sizeof(*shwt));
+ shwt->hwtstamp = ns_to_ktime(ns);
+
+ return false;
+}
+
int b53_ptp_init(struct b53_device *dev)
{
mutex_init(&dev->ptp_mutex);
diff --git a/drivers/net/dsa/b53/b53_ptp.h b/drivers/net/dsa/b53/b53_ptp.h
index 5cd2fd9621a2..3b3437870c55 100644
--- a/drivers/net/dsa/b53/b53_ptp.h
+++ b/drivers/net/dsa/b53/b53_ptp.h
@@ -9,11 +9,15 @@
#include "b53_priv.h"
+#define SKB_PTP_TYPE(__skb) (*(unsigned int *)((__skb)->cb))
+
#ifdef CONFIG_B53_PTP
int b53_ptp_init(struct b53_device *dev);
void b53_ptp_exit(struct b53_device *dev);
int b53_get_ts_info(struct dsa_switch *ds, int port,
struct ethtool_ts_info *info);
+bool b53_port_rxtstamp(struct dsa_switch *ds, int port, struct sk_buff *skb,
+ unsigned int type);
#else /* !CONFIG_B53_PTP */
static inline int b53_ptp_init(struct b53_device *dev)
@@ -31,5 +35,11 @@ static inline int b53_get_ts_info(struct dsa_switch *ds, int port,
return -EOPNOTSUPP;
}
+static inline bool b53_port_rxtstamp(struct dsa_switch *ds, int port,
+ struct sk_buff *skb, unsigned int type)
+{
+ return false;
+}
+
#endif
#endif
diff --git a/include/linux/dsa/b53.h b/include/linux/dsa/b53.h
index 85aa6d9dc53d..542e5e3040d6 100644
--- a/include/linux/dsa/b53.h
+++ b/include/linux/dsa/b53.h
@@ -46,9 +46,32 @@ struct b53_io_ops {
struct phylink_link_state *state);
};
+/* state flags for b53_port_hwtstamp::state */
+enum {
+ B53_HWTSTAMP_ENABLED,
+ B53_HWTSTAMP_TX_IN_PROGRESS,
+};
+
+struct b53_port_hwtstamp {
+ /* Port index */
+ int port_id;
+
+ /* Timestamping state */
+ unsigned long state;
+
+ /* Resources for transmit timestamping */
+ unsigned long tx_tstamp_start;
+ struct sk_buff *tx_skb;
+
+ /* Current timestamp configuration */
+ struct hwtstamp_config tstamp_config;
+};
+
struct b53_port {
u16 vlan_ctl_mask;
struct ethtool_eee eee;
+ /* Per-port timestamping resources */
+ struct b53_port_hwtstamp port_hwtstamp;
};
struct b53_vlan {
@@ -112,3 +135,10 @@ struct b53_device {
#define B53_PTP_OVERFLOW_PERIOD (HZ / 2)
struct delayed_work overflow_work;
};
+
+struct brcm_skb_cb {
+ struct sk_buff *clone;
+ u32 meta_tstamp;
+};
+
+#define BRCM_SKB_CB(skb) ((struct brcm_skb_cb *)(skb)->cb)
diff --git a/net/dsa/tag_brcm.c b/net/dsa/tag_brcm.c
index 96dbb8ee2fee..85dc47c22008 100644
--- a/net/dsa/tag_brcm.c
+++ b/net/dsa/tag_brcm.c
@@ -9,6 +9,7 @@
#include <linux/etherdevice.h>
#include <linux/list.h>
#include <linux/slab.h>
+#include <linux/dsa/b53.h>
#include "dsa_priv.h"
@@ -31,7 +32,10 @@
/* 6th byte in the tag */
#define BRCM_LEG_PORT_ID (0xf)
-/* Newer Broadcom tag (4 bytes) */
+/* Newer Broadcom tag (4 bytes)
+ * For egress, when opcode = 0001, additional 4 bytes are used for
+ * the time stamp.
+ */
#define BRCM_TAG_LEN 4
/* Tag is constructed and desconstructed using byte by byte access
@@ -136,19 +140,26 @@ static struct sk_buff *brcm_tag_xmit_ll(struct sk_buff *skb,
*/
static struct sk_buff *brcm_tag_rcv_ll(struct sk_buff *skb,
struct net_device *dev,
- unsigned int offset)
+ unsigned int offset,
+ int *tag_len)
{
int source_port;
u8 *brcm_tag;
+ u32 tstamp;
+
+ *tag_len = 8;

I believe you have to do this in a two step process, first check that you can pull 4 bytes, read the Broadcom tag's opcode, then pull the additional 4 bytes if the opcode is 1.

- if (unlikely(!pskb_may_pull(skb, BRCM_TAG_LEN)))
+ if (unlikely(!pskb_may_pull(skb, *tag_len)))
return NULL;
brcm_tag = skb->data - offset;
- /* The opcode should never be different than 0b000 */
- if (unlikely((brcm_tag[0] >> BRCM_OPCODE_SHIFT) & BRCM_OPCODE_MASK))
- return NULL;
+ if ((brcm_tag[0] >> BRCM_OPCODE_SHIFT) & BRCM_OPCODE_MASK) {
+ tstamp = brcm_tag[4] << 24 | brcm_tag[5] << 16 | brcm_tag[6] << 8 | brcm_tag[7];
+ BRCM_SKB_CB(skb)->meta_tstamp = tstamp;
+ } else {
+ *tag_len = BRCM_TAG_LEN;
+ }
/* We should never see a reserved reason code without knowing how to
* handle it
@@ -164,7 +175,7 @@ static struct sk_buff *brcm_tag_rcv_ll(struct sk_buff *skb,
return NULL;
/* Remove Broadcom tag and update checksum */
- skb_pull_rcsum(skb, BRCM_TAG_LEN);
+ skb_pull_rcsum(skb, *tag_len);
dsa_default_offload_fwd_mark(skb);
@@ -184,13 +195,14 @@ static struct sk_buff *brcm_tag_xmit(struct sk_buff *skb,
static struct sk_buff *brcm_tag_rcv(struct sk_buff *skb, struct net_device *dev)
{
struct sk_buff *nskb;
+ int tag_len;
/* skb->data points to the EtherType, the tag is right before it */
- nskb = brcm_tag_rcv_ll(skb, dev, 2);
+ nskb = brcm_tag_rcv_ll(skb, dev, 2, &tag_len);
if (!nskb)
return nskb;
- dsa_strip_etype_header(skb, BRCM_TAG_LEN);
+ dsa_strip_etype_header(skb, tag_len);
return nskb;
}
@@ -295,8 +307,10 @@ static struct sk_buff *brcm_tag_xmit_prepend(struct sk_buff *skb,
static struct sk_buff *brcm_tag_rcv_prepend(struct sk_buff *skb,
struct net_device *dev)
{
+ int tag_len;
+
/* tag is prepended to the packet */
- return brcm_tag_rcv_ll(skb, dev, ETH_HLEN);
+ return brcm_tag_rcv_ll(skb, dev, ETH_HLEN, &tag_len);
}
static const struct dsa_device_ops brcm_prepend_netdev_ops = {


--
Florian