quoted

diff --git a/drivers/ptp/ptp_clock.c b/drivers/ptp/ptp_clock.c
index 54b9f54ac0b2..b7a8cf27c349 100644
--- a/drivers/ptp/ptp_clock.c
+++ b/drivers/ptp/ptp_clock.c

@@ -450,6 +450,33 @@ void ptp_cancel_worker_sync(struct ptp_clock *ptp)
 }
 EXPORT_SYMBOL(ptp_cancel_worker_sync);

+ktime_t ptp_get_timestamp(int index,
+                       const struct skb_shared_hwtstamps *hwtstamps,
+                       bool cycles)
+{
+     char name[PTP_CLOCK_NAME_LEN] = "";
+     struct ptp_clock *ptp;
+     struct device *dev;
+     ktime_t ts;
+
+     snprintf(name, PTP_CLOCK_NAME_LEN, "ptp%d", index);
+     dev = class_find_device_by_name(ptp_class, name);

This seems expensive for every single Rx frame in a busy PTP network.
Can't this be cached in the socket?

I thought that PTP packages are rare and that bloating the socket is
not welcome.
I'll try to implement some caching.

quoted

--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h

@@ -564,7 +564,10 @@ static inline bool skb_frag_must_loop(struct page *p)
  * &skb_shared_info. Use skb_hwtstamps() to get a pointer.
  */
 struct skb_shared_hwtstamps {
-     ktime_t hwtstamp;
+     union {
+             ktime_t hwtstamp;
+             void *phc_data;

needs kdoc update

Sorry, I totally forgot that. I'll fix it.

quoted

@@ -886,18 +885,32 @@ void __sock_recv_timestamp(struct msghdr *msg, struct sock *sk,
      if (shhwtstamps &&
          (sk->sk_tsflags & SOF_TIMESTAMPING_RAW_HARDWARE) &&
          !skb_is_swtx_tstamp(skb, false_tstamp)) {
-             if (sk->sk_tsflags & SOF_TIMESTAMPING_BIND_PHC)
-                     hwtstamp = ptp_convert_timestamp(&shhwtstamps->hwtstamp,
-                                                      sk->sk_bind_phc);
+             rcu_read_lock();
+             orig_dev = dev_get_by_napi_id(skb_napi_id(skb));
+             if (orig_dev) {
+                     if_index = orig_dev->ifindex;
+                     if (skb_shinfo(skb)->tx_flags & SKBTX_HW_TSTAMP_PHC)
+                             phc_index = ethtool_get_phc(orig_dev);

again, this is something that can be cached, no?

I'll try to implement some caching.

Thanks for your review!

Gerhard