ptp: Add adjphase function to support phase offset control.

Adds adjust phase function to take advantage of a PHC
clock's hardware filtering capability that uses phase offset
control word instead of frequency offset control word.

Signed-off-by: Vincent Cheng <[e-mail]>
Reviewed-by: Richard Cochran <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/ptp/ptp_clock.c

···
 		else
 			err = ops->adjfreq(ops, ppb);
 		ptp->dialed_frequency = tx->freq;
+	} else if (tx->modes & ADJ_OFFSET) {
+		if (ops->adjphase)
+			err = ops->adjphase(ops, tx->offset);
 	} else if (tx->modes == 0) {
 		tx->freq = ptp->dialed_frequency;
 		err = 0;

include/linux/ptp_clock_kernel.h

···
 };
 
 /**
- * struct ptp_clock_info - decribes a PTP hardware clock
+ * struct ptp_clock_info - describes a PTP hardware clock
  *
  * @owner:     The clock driver should set to THIS_MODULE.
  * @name:      A short "friendly name" to identify the clock and to
···
  *            the @adjfine method instead.
  *            parameter delta: Desired frequency offset from nominal frequency
  *            in parts per billion
+ *
+ * @adjphase:  Adjusts the phase offset of the hardware clock.
+ *             parameter delta: Desired change in nanoseconds.
  *
  * @adjtime:  Shifts the time of the hardware clock.
  *            parameter delta: Desired change in nanoseconds.
···
 	struct ptp_pin_desc *pin_config;
 	int (*adjfine)(struct ptp_clock_info *ptp, long scaled_ppm);
 	int (*adjfreq)(struct ptp_clock_info *ptp, s32 delta);
+	int (*adjphase)(struct ptp_clock_info *ptp, s32 phase);
 	int (*adjtime)(struct ptp_clock_info *ptp, s64 delta);
 	int (*gettime64)(struct ptp_clock_info *ptp, struct timespec64 *ts);
 	int (*gettimex64)(struct ptp_clock_info *ptp, struct timespec64 *ts,