From d8d26354191399627bac9cf0da0667b0f5178686 Mon Sep 17 00:00:00 2001 From: Richard Cochran Date: Tue, 8 Nov 2016 22:49:16 +0100 Subject: ptp: Introduce a high resolution frequency adjustment method. 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 Suggested-by: Ulrik De Bie Signed-off-by: David S. Miller --- drivers/ptp/ptp_clock.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) (limited to 'drivers/ptp') diff --git a/drivers/ptp/ptp_clock.c b/drivers/ptp/ptp_clock.c index 86280b7e41f3..9c13381b6966 100644 --- a/drivers/ptp/ptp_clock.c +++ b/drivers/ptp/ptp_clock.c @@ -153,7 +153,10 @@ 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; - err = ops->adjfreq(ops, ppb); + 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) { tx->freq = ptp->dialed_frequency; -- cgit v1.2.3-59-g8ed1b