From 4f9bac039a64f6306b613a0d90e6b7e75d7ab0c4 Mon Sep 17 00:00:00 2001 From: Vitaly Kuznetsov Date: Thu, 18 May 2017 10:46:03 -0700 Subject: [PATCH] hv_utils: drop .getcrosststamp() support from PTP driver Turns out that our implementation of .getcrosststamp() never actually worked. Hyper-V is sending time samples every 5 seconds and this is too much for get_device_system_crosststamp() as it's interpolation algorithm (which nobody is currently using in kernel, btw) accounts for a 'slow' device but we're not slow in Hyper-V, our time reference is too far away. .getcrosststamp() is not currently used, get_device_system_crosststamp() almost always returns -EINVAL and client falls back to using PTP_SYS_OFFSET so this patch doesn't change much. I also tried doing interpolation manually (e.g. the same way hv_ptp_gettime() works and it turns out that we're getting even lower quality: PTP_SYS_OFFSET_PRECISE with manual interpolation: * PHC0 0 3 37 4 -3974ns[-5338ns] +/- 977ns * PHC0 0 3 77 7 +2227ns[+3184ns] +/- 576ns * PHC0 0 3 177 10 +3060ns[+5220ns] +/- 548ns * PHC0 0 3 377 12 +3937ns[+4371ns] +/- 1414ns * PHC0 0 3 377 6 +764ns[+1240ns] +/- 1047ns * PHC0 0 3 377 7 -1210ns[-3731ns] +/- 479ns * PHC0 0 3 377 9 +153ns[-1019ns] +/- 406ns * PHC0 0 3 377 12 -872ns[-1793ns] +/- 443ns * PHC0 0 3 377 5 +701ns[+3599ns] +/- 426ns * PHC0 0 3 377 5 -923ns[ -375ns] +/- 1062ns PTP_SYS_OFFSET: * PHC0 0 3 7 5 +72ns[+8020ns] +/- 251ns * PHC0 0 3 17 5 -885ns[-3661ns] +/- 254ns * PHC0 0 3 37 6 -454ns[-5732ns] +/- 258ns * PHC0 0 3 77 10 +1183ns[+3754ns] +/- 164ns * PHC0 0 3 377 5 +579ns[+1137ns] +/- 110ns * PHC0 0 3 377 7 +501ns[+1064ns] +/- 96ns * PHC0 0 3 377 9 +1641ns[+3342ns] +/- 106ns * PHC0 0 3 377 8 -47ns[ +77ns] +/- 160ns * PHC0 0 3 377 5 +54ns[ +107ns] +/- 102ns * PHC0 0 3 377 8 -354ns[ -617ns] +/- 89ns This fact wasn't noticed during the initial testing of the PTP device somehow but got revealed now. Let's just drop .getcrosststamp() implementation for now as it doesn't seem to be suitable for us. Signed-off-by: Vitaly Kuznetsov Signed-off-by: K. Y. Srinivasan Signed-off-by: Greg Kroah-Hartman --- drivers/hv/hv_util.c | 36 ------------------------------------ 1 file changed, 36 deletions(-) diff --git a/drivers/hv/hv_util.c b/drivers/hv/hv_util.c index 186b10083c55..2849143bf6f0 100644 --- a/drivers/hv/hv_util.c +++ b/drivers/hv/hv_util.c @@ -248,7 +248,6 @@ static struct adj_time_work wrk; static struct { u64 host_time; u64 ref_time; - struct system_time_snapshot snap; spinlock_t lock; } host_ts; @@ -281,7 +280,6 @@ static inline void adj_guesttime(u64 hosttime, u64 reftime, u8 adj_flags) cur_reftime = hyperv_cs->read(hyperv_cs); host_ts.host_time = hosttime; host_ts.ref_time = cur_reftime; - ktime_get_snapshot(&host_ts.snap); /* * TimeSync v4 messages contain reference time (guest's Hyper-V @@ -538,46 +536,12 @@ static int hv_ptp_gettime(struct ptp_clock_info *info, struct timespec64 *ts) return 0; } -static int hv_ptp_get_syncdevicetime(ktime_t *device, - struct system_counterval_t *system, - void *ctx) -{ - system->cs = hyperv_cs; - system->cycles = host_ts.ref_time; - *device = ns_to_ktime((host_ts.host_time - WLTIMEDELTA) * 100); - - return 0; -} - -static int hv_ptp_getcrosststamp(struct ptp_clock_info *ptp, - struct system_device_crosststamp *xtstamp) -{ - unsigned long flags; - int ret; - - spin_lock_irqsave(&host_ts.lock, flags); - - /* - * host_ts contains the last time sample from the host and the snapshot - * of system time. We don't need to calculate the time delta between - * the reception and now as get_device_system_crosststamp() does the - * required interpolation. - */ - ret = get_device_system_crosststamp(hv_ptp_get_syncdevicetime, - NULL, &host_ts.snap, xtstamp); - - spin_unlock_irqrestore(&host_ts.lock, flags); - - return ret; -} - static struct ptp_clock_info ptp_hyperv_info = { .name = "hyperv", .enable = hv_ptp_enable, .adjtime = hv_ptp_adjtime, .adjfreq = hv_ptp_adjfreq, .gettime64 = hv_ptp_gettime, - .getcrosststamp = hv_ptp_getcrosststamp, .settime64 = hv_ptp_settime, .owner = THIS_MODULE, }; -- 2.20.1