diff options
| author | David Woodhouse <dwmw@amazon.co.uk> | 2026-01-30 17:36:06 +0000 |
|---|---|---|
| committer | Jakub Kicinski <kuba@kernel.org> | 2026-02-02 18:06:01 -0800 |
| commit | 562f59fe32914a10af8554634866bd0b56257060 (patch) | |
| tree | 7ea3bf188ab00d58af414ecd44794e18061011c8 | |
| parent | ac1e7404924cb4a1ab2993e64151e2ad2f461ab3 (diff) | |
ptp: ptp_vmclock: return TAI not UTC
To output UTC would involve complex calculations about whether the time
elapsed since the reference time has crossed the end of the month when
a leap second takes effect. I've prototyped that, but it made me sad.
Much better to report TAI, which is what PHCs should do anyway.
And much much simpler.
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: Babis Chalios <bchalios@amazon.es>
Tested-by: Takahiro Itazuri <itazur@amazon.com>
Link: https://patch.msgid.link/20260130173704.12575-8-itazur@amazon.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
| -rw-r--r-- | drivers/ptp/ptp_vmclock.c | 10 |
1 files changed, 5 insertions, 5 deletions
diff --git a/drivers/ptp/ptp_vmclock.c b/drivers/ptp/ptp_vmclock.c index b6e9d4c96ba0..c7c75e19f4dd 100644 --- a/drivers/ptp/ptp_vmclock.c +++ b/drivers/ptp/ptp_vmclock.c @@ -83,13 +83,13 @@ static uint64_t mul_u64_u64_shr_add_u64(uint64_t *res_hi, uint64_t delta, static bool tai_adjust(struct vmclock_abi *clk, uint64_t *sec) { - if (likely(clk->time_type == VMCLOCK_TIME_UTC)) + if (clk->time_type == VMCLOCK_TIME_TAI) return true; - if (clk->time_type == VMCLOCK_TIME_TAI && + if (clk->time_type == VMCLOCK_TIME_UTC && (le64_to_cpu(clk->flags) & VMCLOCK_FLAG_TAI_OFFSET_VALID)) { if (sec) - *sec += (int16_t)le16_to_cpu(clk->tai_offset_sec); + *sec -= (int16_t)le16_to_cpu(clk->tai_offset_sec); return true; } return false; @@ -350,9 +350,9 @@ static struct ptp_clock *vmclock_ptp_register(struct device *dev, return NULL; } - /* Only UTC, or TAI with offset */ + /* Accept TAI directly, or UTC with valid offset for conversion to TAI */ if (!tai_adjust(st->clk, NULL)) { - dev_info(dev, "vmclock does not provide unambiguous UTC\n"); + dev_info(dev, "vmclock does not provide unambiguous time\n"); return NULL; } |