netdev - [PATCH net-next v4 2/6] ptp: Request cycles for TX timestamp

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Date:   Fri,  6 May 2022 22:01:38 +0200
From:   Gerhard Engleder <gerhard@...leder-embedded.com>
To:     richardcochran@...il.com, vinicius.gomes@...el.com,
        yangbo.lu@....com, davem@...emloft.net, kuba@...nel.org
Cc:     mlichvar@...hat.com, willemb@...gle.com, kafai@...com,
        jonathan.lemon@...il.com, netdev@...r.kernel.org,
        Gerhard Engleder <gerhard@...leder-embedded.com>
Subject: [PATCH net-next v4 2/6] ptp: Request cycles for TX timestamp

The free running cycle counter of physical clocks called cycles shall be
used for hardware timestamps to enable synchronisation.

Introduce new flag SKBTX_HW_TSTAMP_USE_CYCLES, which signals driver to
provide a TX timestamp based on cycles if cycles are supported.

Signed-off-by: Gerhard Engleder <gerhard@...leder-embedded.com>
Acked-by: Richard Cochran <richardcochran@...il.com>
---
 include/linux/skbuff.h |  7 ++++++-
 net/socket.c           | 11 ++++++++++-
 2 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 5c2599e3fe7d..4d49503bdc4d 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -615,6 +615,9 @@ enum {
 	/* device driver is going to provide hardware time stamp */
 	SKBTX_IN_PROGRESS = 1 << 2,
 
+	/* generate hardware time stamp based on cycles if supported */
+	SKBTX_HW_TSTAMP_USE_CYCLES = 1 << 3,
+
 	/* generate wifi status information (where possible) */
 	SKBTX_WIFI_STATUS = 1 << 4,
 
@@ -624,7 +627,9 @@ enum {
 
 #define SKBTX_ANY_SW_TSTAMP	(SKBTX_SW_TSTAMP    | \
 				 SKBTX_SCHED_TSTAMP)
-#define SKBTX_ANY_TSTAMP	(SKBTX_HW_TSTAMP | SKBTX_ANY_SW_TSTAMP)
+#define SKBTX_ANY_TSTAMP	(SKBTX_HW_TSTAMP | \
+				 SKBTX_HW_TSTAMP_USE_CYCLES | \
+				 SKBTX_ANY_SW_TSTAMP)
 
 /* Definitions for flags in struct skb_shared_info */
 enum {
diff --git a/net/socket.c b/net/socket.c
index f0c39c874665..5c1c5e6100e1 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -683,9 +683,18 @@ void __sock_tx_timestamp(__u16 tsflags, __u8 *tx_flags)
 {
 	u8 flags = *tx_flags;
 
-	if (tsflags & SOF_TIMESTAMPING_TX_HARDWARE)
+	if (tsflags & SOF_TIMESTAMPING_TX_HARDWARE) {
 		flags |= SKBTX_HW_TSTAMP;
 
+		/* PTP hardware clocks can provide a free running cycle counter
+		 * as a time base for virtual clocks. Tell driver to use the
+		 * free running cycle counter for timestamp if socket is bound
+		 * to virtual clock.
+		 */
+		if (tsflags & SOF_TIMESTAMPING_BIND_PHC)
+			flags |= SKBTX_HW_TSTAMP_USE_CYCLES;
+	}
+
 	if (tsflags & SOF_TIMESTAMPING_TX_SOFTWARE)
 		flags |= SKBTX_SW_TSTAMP;
 
-- 
2.20.1