net: ethernet: ti: cpts: switch to use new .gettimex64() interface

The CPTS HW latches and saves CPTS counter value in CPTS fifo immediately
after writing to CPSW_CPTS_PUSH.TS_PUSH (bit 0), so the total time that the
driver needs to read the CPTS timestamp is the time required CPSW_CPTS_PUSH
write to actually reach HW.

Hence switch CPTS driver to implement new .gettimex64() callback for more
precise measurement of the offset between a PHC and the system clock which
is measured as time between
  write(CPSW_CPTS_PUSH)
  read(CPSW_CPTS_PUSH)
Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>
Acked-by: Richard Cochran <richardcochran@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/ti/cpts.c

@@ -203,9 +203,13 @@ static u64 cpts_systim_read(const struct cyclecounter *cc)
 	return READ_ONCE(cpts->cur_timestamp);
 }
 
-static void cpts_update_cur_time(struct cpts *cpts, int match)
+static void cpts_update_cur_time(struct cpts *cpts, int match,
+				 struct ptp_system_timestamp *sts)
 {
+	ptp_read_system_prets(sts);
 	cpts_write32(cpts, TS_PUSH, ts_push);
+	cpts_read32(cpts, ts_push);
+	ptp_read_system_postts(sts);
 
 	if (cpts_fifo_read(cpts, match) && match != -1)
 		dev_err(cpts->dev, "cpts: unable to obtain a time stamp\n");
@@ -234,7 +238,7 @@ static int cpts_ptp_adjfreq(struct ptp_clock_info *ptp, s32 ppb)
 
 	cpts->mult_new = neg_adj ? mult - diff : mult + diff;
 
-	cpts_update_cur_time(cpts, CPTS_EV_PUSH);
+	cpts_update_cur_time(cpts, CPTS_EV_PUSH, NULL);
 
 	spin_unlock_irqrestore(&cpts->lock, flags);
 
@@ -253,15 +257,17 @@ static int cpts_ptp_adjtime(struct ptp_clock_info *ptp, s64 delta)
 	return 0;
 }
 
-static int cpts_ptp_gettime(struct ptp_clock_info *ptp, struct timespec64 *ts)
+static int cpts_ptp_gettimeex(struct ptp_clock_info *ptp,
+			      struct timespec64 *ts,
+			      struct ptp_system_timestamp *sts)
 {
-	u64 ns;
-	unsigned long flags;
 	struct cpts *cpts = container_of(ptp, struct cpts, info);
+	unsigned long flags;
+	u64 ns;
 
 	spin_lock_irqsave(&cpts->lock, flags);
 
-	cpts_update_cur_time(cpts, CPTS_EV_PUSH);
+	cpts_update_cur_time(cpts, CPTS_EV_PUSH, sts);
 
 	ns = timecounter_read(&cpts->tc);
 	spin_unlock_irqrestore(&cpts->lock, flags);
@@ -302,7 +308,7 @@ static long cpts_overflow_check(struct ptp_clock_info *ptp)
 
 	spin_lock_irqsave(&cpts->lock, flags);
 
-	cpts_update_cur_time(cpts, -1);
+	cpts_update_cur_time(cpts, -1, NULL);
 
 	ns = timecounter_read(&cpts->tc);
 
@@ -326,7 +332,7 @@ static const struct ptp_clock_info cpts_info = {
 	.pps		= 0,
 	.adjfreq	= cpts_ptp_adjfreq,
 	.adjtime	= cpts_ptp_adjtime,
-	.gettime64	= cpts_ptp_gettime,
+	.gettimex64	= cpts_ptp_gettimeex,
 	.settime64	= cpts_ptp_settime,
 	.enable		= cpts_ptp_enable,
 	.do_aux_work	= cpts_overflow_check,