From nobody Sun Feb 8 09:10:09 2026 Received: from pdx-out-011.esa.us-west-2.outbound.mail-perimeter.amazon.com (pdx-out-011.esa.us-west-2.outbound.mail-perimeter.amazon.com [52.35.192.45]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id EF4123A7F58; Wed, 21 Jan 2026 14:35:02 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=52.35.192.45 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769006104; cv=none; b=oIyV7/VKs+fnxudjjJGaoW/bHjtbddsGCB804SZ5mpm2+xqXOYPgw6eSpGG/sYaBOL8WsQGM4XbEm8v3jYHShTmFUKLXttXIwZaOqHp84nEnOMn8Kg2vqvFc8MwoB5c8hme1a5KInHf/5I2QpgObc9sMC8Wj3ncX8JlLSizSdiE= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769006104; c=relaxed/simple; bh=4kTJcLmYGzRCj4IKX4oNLKlCTvwFwEiSzIa5dY7keno=; h=From:To:CC:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=psBlANAyqCPb/+Tdqsl2AVXmVE6w+MKuWliRgxREuhSvngff5IC109sAVer3oF7p50vErnffY6fkmQiLpSH/tn1rm/rIMVRf9eKAVRineXLazAx3eEWPI5tRdpyDuec4jeEIBAGyLIQXz4YiRFiyvjp1H4fB4CmvNabyZA2JdJ0= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=amazon.com; spf=pass smtp.mailfrom=amazon.co.uk; dkim=pass (2048-bit key) header.d=amazon.com header.i=@amazon.com header.b=UODvhtRk; arc=none smtp.client-ip=52.35.192.45 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=amazon.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=amazon.co.uk Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=amazon.com header.i=@amazon.com header.b="UODvhtRk" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amazon.com; i=@amazon.com; q=dns/txt; s=amazoncorp2; t=1769006102; x=1800542102; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=0rhk6SMiUX4DX71gJT40pzZWSzRz9RPlP3yDXcP1Qj8=; b=UODvhtRk1GDZ5HXknWzBcUVt8lmZmP7r1Ik16hBfUU6OWkL3a/euCWsq o9e4e/rty55mMNAGSW7AVsjvkaCWE64yZhdjnVOosf8/NlnSjMzgsQgwq c5lo40zq+FeGCb3JU52gKNYFoPvZxkPpJPFRC7KHTskyb08f+dvguifVf 7AlV6m2NER6HhDol3QqA0fUx2YdLs4dsqnzcZQI4fd/dsG4MJnx+RS5Bk o+HM++5DInuWMITDfrkwTVkcTRTWqTm/xXaAfHe2dhbhXPn05YqrW192p JPc4Zq6GKr0MX1TEpO3z2lZkSCAJiLVSBzHdWUx34m7LPxql3m0CMYNv5 g==; X-CSE-ConnectionGUID: XfwFkXjbQFi3pm5sENoVEA== X-CSE-MsgGUID: +/0dyjK6QTuQ7fAQU9OwOg== X-IronPort-AV: E=Sophos;i="6.21,242,1763424000"; d="scan'208";a="11093535" Received: from ip-10-5-6-203.us-west-2.compute.internal (HELO smtpout.naws.us-west-2.prod.farcaster.email.amazon.dev) ([10.5.6.203]) by internal-pdx-out-011.esa.us-west-2.outbound.mail-perimeter.amazon.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 21 Jan 2026 14:35:02 +0000 Received: from EX19MTAUWC002.ant.amazon.com [205.251.233.51:18279] by smtpin.naws.us-west-2.prod.farcaster.email.amazon.dev [10.0.14.244:2525] with esmtp (Farcaster) id 40835c61-feff-4f8f-89b1-4b3d3f82deb9; Wed, 21 Jan 2026 14:35:02 +0000 (UTC) X-Farcaster-Flow-ID: 40835c61-feff-4f8f-89b1-4b3d3f82deb9 Received: from EX19D001UWA001.ant.amazon.com (10.13.138.214) by EX19MTAUWC002.ant.amazon.com (10.250.64.143) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA) id 15.2.2562.35; Wed, 21 Jan 2026 14:35:00 +0000 Received: from dev-dsk-itazur-1b-11e7fc0f.eu-west-1.amazon.com (172.19.66.53) by EX19D001UWA001.ant.amazon.com (10.13.138.214) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA) id 15.2.2562.35; Wed, 21 Jan 2026 14:34:57 +0000 From: Takahiro Itazuri To: , , , , , , , , , CC: , , , Babis Chalios , "Alexander Graf" , , Marco Cali , David Woodhouse , "Takahiro Itazuri" Subject: [PATCH v6 7/7] ptp: ptp_vmclock: return TAI not UTC Date: Wed, 21 Jan 2026 14:33:44 +0000 Message-ID: <20260121143402.3092-8-itazur@amazon.com> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260121143402.3092-1-itazur@amazon.com> References: <20260121143402.3092-1-itazur@amazon.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-ClientProxiedBy: EX19D040UWB001.ant.amazon.com (10.13.138.82) To EX19D001UWA001.ant.amazon.com (10.13.138.214) Content-Type: text/plain; charset="utf-8" From: David Woodhouse 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 Signed-off-by: Babis Chalios --- drivers/ptp/ptp_vmclock.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/drivers/ptp/ptp_vmclock.c b/drivers/ptp/ptp_vmclock.c index 55ec3cda3995..6cf63a86c997 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_h= i, uint64_t delta, =20 static bool tai_adjust(struct vmclock_abi *clk, uint64_t *sec) { - if (likely(clk->time_type =3D=3D VMCLOCK_TIME_UTC)) + if (clk->time_type =3D=3D VMCLOCK_TIME_TAI) return true; =20 - if (clk->time_type =3D=3D VMCLOCK_TIME_TAI && + if (clk->time_type =3D=3D VMCLOCK_TIME_UTC && (le64_to_cpu(clk->flags) & VMCLOCK_FLAG_TAI_OFFSET_VALID)) { if (sec) - *sec +=3D (int16_t)le16_to_cpu(clk->tai_offset_sec); + *sec -=3D (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 de= vice *dev, return NULL; } =20 - /* 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; } =20 --=20 2.47.3