ptp: Introduce a high resolution frequency adjustment method. (d8d26354) · Commits · 戴 / test

The internal PTP Hardware Clock (PHC) interface limits the resolution for frequency adjustments to one part per billion. However, some hardware devices allow finer adjustment, and making use of the increased resolution improves synchronization measurably on such devices. This patch adds an alternative method that allows finer frequency tuning by passing the scaled ppm value to PHC drivers. This value comes from user space, and it has a resolution of about 0.015 ppb. We also deprecate the older method, anticipating its removal once existing drivers have been converted over. Signed-off-by:

Richard Cochran <richardcochran@gmail.com> Suggested-by:

Ulrik De Bie <ulrik.debie-os@e2big.org> Signed-off-by:

David S. Miller <davem@davemloft.net>

drivers/ptp/ptp_clock.c

+4 −1

Original line number	Diff line number	Diff line
		@@ -153,6 +153,9 @@ static int ptp_clock_adjtime(struct posix_clock pc, struct timex tx)
		s32 ppb = scaled_ppm_to_ppb(tx->freq);
		if (ppb > ops->max_adj \|\| ppb < -ops->max_adj)
		return -ERANGE;
		if (ops->adjfine)
		err = ops->adjfine(ops, tx->freq);
		else
		err = ops->adjfreq(ops, ppb);
		ptp->dialed_frequency = tx->freq;
		} else if (tx->modes == 0) {

include/linux/ptp_clock_kernel.h

+8 −0

Original line number	Diff line number	Diff line
		@@ -58,7 +58,14 @@ struct system_device_crosststamp;
		*
		* clock operations
		*
		* @adjfine: Adjusts the frequency of the hardware clock.
		* parameter scaled_ppm: Desired frequency offset from
		* nominal frequency in parts per million, but with a
		* 16 bit binary fractional field.
		*
		* @adjfreq: Adjusts the frequency of the hardware clock.
		* This method is deprecated. New drivers should implement
		* the @adjfine method instead.
		* parameter delta: Desired frequency offset from nominal frequency
		* in parts per billion
		*
		@@ -108,6 +115,7 @@ struct ptp_clock_info {
		int n_pins;
		int pps;
		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 (adjtime)(struct ptp_clock_info ptp, s64 delta);
		int (gettime64)(struct ptp_clock_info ptp, struct timespec64 *ts);

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