From d8d26354191399627bac9cf0da0667b0f5178686 Mon Sep 17 00:00:00 2001 From: Richard Cochran Date: Tue, 8 Nov 2016 22:49:16 +0100 Subject: [PATCH] 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 ++++- include/linux/ptp_clock_kernel.h | 8 ++++++++ 2 files changed, 12 insertions(+), 1 deletion(-) 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; diff --git a/include/linux/ptp_clock_kernel.h b/include/linux/ptp_clock_kernel.h index 5ad54fc66cf0..b76d47aba564 100644 --- a/include/linux/ptp_clock_kernel.h +++ b/include/linux/ptp_clock_kernel.h @@ -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); -- 2.20.1