[PATCH net-next] net: stmmac: ptp: switch to gettimex64() interface

[James Clark <jjc@jclark.com>]

The stmmac PTP support currently implements the gettime64 callback to
retrieve the hardware clock time. Update the implementation to provide
the gettimex64 callback instead, adding support for the
PTP_SYS_OFFSET_EXTENDED ioctl.

The system clock readings are taken around the read of the nanoseconds
register in get_systime(), so get_systime() gains a ptp_system_timestamp
argument. rmb() is used to ensure proper ordering on weakly ordered
architectures.

Assisted-by: LLM
Signed-off-by: James Clark <jjc@jclark.com>
---
Tested on a Radxa ZERO 3E (RK3566, DWMAC 4/5) running net-next.
Width of the interval between the two system clock readings
bracketing each PHC read (2000 calls of 25 samples each):

                                         min      median
Before patch (PTP_SYS_OFFSET):           875 ns   1167 ns
After patch (PTP_SYS_OFFSET_EXTENDED):   291 ns    584 ns

On this board the 24 MHz arch timer counter advances in steps of 7
(~292 ns), so all intervals are multiples of that.

 drivers/net/ethernet/stmicro/stmmac/hwif.h      |  5 ++++-
 .../ethernet/stmicro/stmmac/stmmac_hwtstamp.c   |  9 ++++++++-
 .../net/ethernet/stmicro/stmmac/stmmac_ptp.c    | 17 ++++++++++-------
 .../ethernet/stmicro/stmmac/stmmac_selftests.c  |  4 ++--
 drivers/net/ethernet/stmicro/stmmac/stmmac_tc.c |  3 ++-
 5 files changed, 26 insertions(+), 12 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/hwif.h b/drivers/net/ethernet/stmicro/stmmac/hwif.h
index a8a5c8fdd..6efbfe501 100644
--- a/drivers/net/ethernet/stmicro/stmmac/hwif.h
+++ b/drivers/net/ethernet/stmicro/stmmac/hwif.h
@@ -493,6 +493,8 @@ struct stmmac_ops {
 #define stmmac_fpe_map_preemption_class(__priv, __args...) \
 	stmmac_do_callback(__priv, mac, fpe_map_preemption_class, __args)
 
+struct ptp_system_timestamp;
+
 /* PTP and HW Timer helpers */
 struct stmmac_hwtimestamp {
 	void (*config_hw_tstamping) (void __iomem *ioaddr, u32 data);
@@ -502,7 +504,8 @@ struct stmmac_hwtimestamp {
 	int (*config_addend) (void __iomem *ioaddr, u32 addend);
 	int (*adjust_systime) (void __iomem *ioaddr, u32 sec, u32 nsec,
 			       int add_sub, int gmac4);
-	void (*get_systime) (void __iomem *ioaddr, u64 *systime);
+	void (*get_systime)(void __iomem *ioaddr, u64 *systime,
+			    struct ptp_system_timestamp *sts);
 	void (*get_ptptime)(void __iomem *ioaddr, u64 *ptp_time);
 	void (*timestamp_interrupt)(struct stmmac_priv *priv);
 	void (*hwtstamp_correct_latency)(struct stmmac_priv *priv);
diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_hwtstamp.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_hwtstamp.c
index b9a985fa7..a556b49aa 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_hwtstamp.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_hwtstamp.c
@@ -183,7 +183,8 @@ static int adjust_systime(void __iomem *ioaddr, u32 sec, u32 nsec,
 					 10, 100000);
 }
 
-static void get_systime(void __iomem *ioaddr, u64 *systime)
+static void get_systime(void __iomem *ioaddr, u64 *systime,
+			struct ptp_system_timestamp *sts)
 {
 	u64 ns, sec0, sec1;
 
@@ -191,8 +192,14 @@ static void get_systime(void __iomem *ioaddr, u64 *systime)
 	sec1 = readl_relaxed(ioaddr + PTP_STSR);
 	do {
 		sec0 = sec1;
+		ptp_read_system_prets(sts);
+		if (sts)
+			rmb();
 		/* Get the TSSS value */
 		ns = readl_relaxed(ioaddr + PTP_STNSR);
+		if (sts)
+			rmb();
+		ptp_read_system_postts(sts);
 		/* Get the TSS value */
 		sec1 = readl_relaxed(ioaddr + PTP_STSR);
 	} while (sec0 != sec1);
diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_ptp.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_ptp.c
index 3bfcc9760..41f0885ab 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_ptp.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_ptp.c
@@ -89,7 +89,8 @@ static int stmmac_adjust_time(struct ptp_clock_info *ptp, s64 delta)
 		u64 cycle_time;
 
 		mutex_lock(&priv->est_lock);
-		priv->ptp_clock_ops.gettime64(&priv->ptp_clock_ops, &current_time);
+		priv->ptp_clock_ops.gettimex64(&priv->ptp_clock_ops, &current_time,
+					       NULL);
 		current_time_ns = timespec64_to_ktime(current_time);
 		time.tv_nsec = priv->est->btr_reserve[0];
 		time.tv_sec = priv->est->btr_reserve[1];
@@ -114,15 +115,17 @@ static int stmmac_adjust_time(struct ptp_clock_info *ptp, s64 delta)
 }
 
 /**
- * stmmac_get_time
+ * stmmac_get_timex
  *
  * @ptp: pointer to ptp_clock_info structure
  * @ts: pointer to hold time/result
+ * @sts: pointer to hold system timestamps around the read, or NULL
  *
  * Description: this function will read the current time from the
  * hardware clock and store it in @ts.
  */
-static int stmmac_get_time(struct ptp_clock_info *ptp, struct timespec64 *ts)
+static int stmmac_get_timex(struct ptp_clock_info *ptp, struct timespec64 *ts,
+			    struct ptp_system_timestamp *sts)
 {
 	struct stmmac_priv *priv =
 	    container_of(ptp, struct stmmac_priv, ptp_clock_ops);
@@ -130,7 +133,7 @@ static int stmmac_get_time(struct ptp_clock_info *ptp, struct timespec64 *ts)
 	u64 ns = 0;
 
 	read_lock_irqsave(&priv->ptp_lock, flags);
-	stmmac_get_systime(priv, priv->ptpaddr, &ns);
+	stmmac_get_systime(priv, priv->ptpaddr, &ns, sts);
 	read_unlock_irqrestore(&priv->ptp_lock, flags);
 
 	*ts = ns_to_timespec64(ns);
@@ -200,7 +203,7 @@ static int stmmac_enable(struct ptp_clock_info *ptp,
 
 		target_ns = cfg->start.tv_nsec + ((u64)cfg->start.tv_sec * NSEC_PER_SEC);
 
-		stmmac_get_systime(priv, priv->ptpaddr, &ns);
+		stmmac_get_systime(priv, priv->ptpaddr, &ns, NULL);
 		if (ns > TIME64_MAX - PTP_SAFE_TIME_OFFSET_NS)
 			return -EINVAL;
 
@@ -304,7 +307,7 @@ const struct ptp_clock_info stmmac_ptp_clock_ops = {
 	.pps = 0,
 	.adjfine = stmmac_adjust_freq,
 	.adjtime = stmmac_adjust_time,
-	.gettime64 = stmmac_get_time,
+	.gettimex64 = stmmac_get_timex,
 	.settime64 = stmmac_set_time,
 	.enable = stmmac_enable,
 };
@@ -321,7 +324,7 @@ const struct ptp_clock_info dwmac1000_ptp_clock_ops = {
 	.pps = 0,
 	.adjfine = stmmac_adjust_freq,
 	.adjtime = stmmac_adjust_time,
-	.gettime64 = stmmac_get_time,
+	.gettimex64 = stmmac_get_timex,
 	.settime64 = stmmac_set_time,
 	.enable = dwmac1000_ptp_enable,
 };
diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_selftests.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_selftests.c
index 6097f312f..2ae4f0e76 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_selftests.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_selftests.c
@@ -1778,7 +1778,7 @@ static int stmmac_test_tbs(struct stmmac_priv *priv)
 		return ret;
 
 	read_lock_irqsave(&priv->ptp_lock, flags);
-	stmmac_get_systime(priv, priv->ptpaddr, &curr_time);
+	stmmac_get_systime(priv, priv->ptpaddr, &curr_time, NULL);
 	read_unlock_irqrestore(&priv->ptp_lock, flags);
 
 	if (!curr_time) {
@@ -1800,7 +1800,7 @@ static int stmmac_test_tbs(struct stmmac_priv *priv)
 
 	/* Check if expected time has elapsed */
 	read_lock_irqsave(&priv->ptp_lock, flags);
-	stmmac_get_systime(priv, priv->ptpaddr, &curr_time);
+	stmmac_get_systime(priv, priv->ptpaddr, &curr_time, NULL);
 	read_unlock_irqrestore(&priv->ptp_lock, flags);
 
 	if ((curr_time - start_time) < STMMAC_TBS_LT_OFFSET)
diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_tc.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_tc.c
index 42a00446e..57ebeb2c1 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_tc.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_tc.c
@@ -1070,7 +1070,8 @@ static int tc_taprio_configure(struct stmmac_priv *priv,
 
 	mutex_lock(&priv->est_lock);
 	/* Adjust for real system time */
-	priv->ptp_clock_ops.gettime64(&priv->ptp_clock_ops, &current_time);
+	priv->ptp_clock_ops.gettimex64(&priv->ptp_clock_ops, &current_time,
+				       NULL);
 	current_time_ns = timespec64_to_ktime(current_time);
 	time = stmmac_calc_tas_basetime(qopt->base_time, current_time_ns,
 					qopt->cycle_time);

base-commit: cfb7793d1bc0f7d90571611979654cf1b3886b29
-- 
2.55.0