From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtpout-02.galae.net (smtpout-02.galae.net [185.246.84.56]) (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 2ED541632C8; Wed, 15 Oct 2025 12:55:28 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=185.246.84.56 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760532931; cv=none; b=GEfnnNCFkNOYwVPjwSfxHn59q3rmOttZYowslBYkN9PYB0IEpG36Rglrm81uhDLx/4AZiabfZ/2Iq2c4KBldHotZAwNRWl2BLgzDXJOj3X5R3u2rOPFCMlS5SmJhIoa4PjWCXTcQSnxQySPDQNcCkpwcSvKbMWOfzhRvesTFh0s= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760532931; c=relaxed/simple; bh=NyCDOZrVB//07BPd6+GXYHFSqEEcVLNlH+OBjCmleEs=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=CdKhKhmhKpbUmr5bUnR91MDavYSUJcm+HckBuhrEP/Qw6ZAwpZX+VWYKEfq7pa6TvAeYcAUvTQbxNVxbD2QaUFx90gEsUTxAM90H4jDFhfukcBJEIH3JbIP8MWS4uRzhOuhK7BdOf8ZgTr9dW20V+ZlM14Mpt3tPLt4s+st46Ts= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=bootlin.com; spf=pass smtp.mailfrom=bootlin.com; dkim=pass (2048-bit key) header.d=bootlin.com header.i=@bootlin.com header.b=CsKF6TcA; arc=none smtp.client-ip=185.246.84.56 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=bootlin.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=bootlin.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=bootlin.com header.i=@bootlin.com header.b="CsKF6TcA" Received: from smtpout-01.galae.net (smtpout-01.galae.net [212.83.139.233]) by smtpout-02.galae.net (Postfix) with ESMTPS id 4967D1A13D8; Wed, 15 Oct 2025 12:55:27 +0000 (UTC) Received: from mail.galae.net (mail.galae.net [212.83.136.155]) by smtpout-01.galae.net (Postfix) with ESMTPS id 1DD15606F9; Wed, 15 Oct 2025 12:55:27 +0000 (UTC) Received: from [127.0.0.1] (localhost [127.0.0.1]) by localhost (Mailerdaemon) with ESMTPSA id 8B304102F22CE; Wed, 15 Oct 2025 14:55:20 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bootlin.com; s=dkim; t=1760532926; h=from:subject:date:message-id:to:cc:mime-version:content-type: content-transfer-encoding:in-reply-to:references; bh=NyCDOZrVB//07BPd6+GXYHFSqEEcVLNlH+OBjCmleEs=; b=CsKF6TcAWd5LfvC7ftYlRfzRDPv4j5akgSTQ45lu65C1SVhGdY9r2HNWLqTrnEUvIMvL9u 8lPLP7bQzTuztsBusuz4954KALlHGlmex6RSYSLvK36KQrJcNmzQDqeRcVct/NL1F5RKvs nBrBEQbvpQ44bMOixhIiGNdsRh1QhAjfK7YiYTfPIkIrJUERSKaOvc/PBP8zsnEJRVnpdK psbdGr56bEveRnQsfaU3yXP2mMxcKpBL8wkQSSt6RTheJ3mo789W89lSSZjJ7mNxRRcvOu Oqf34+rAbXBUUpaLEH7OjF7VG1Azeq2I8FLFeYZ5wryPje6OYDJL0L01S+0UYg== Date: Wed, 15 Oct 2025 14:55:19 +0200 From: Kory Maincent To: Maxime Chevallier Cc: Alexandre Torgue , Jose Abreu , Andrew Lunn , davem@davemloft.net, Eric Dumazet , Jakub Kicinski , Paolo Abeni , Maxime Coquelin , Richard Cochran , Russell King , Alexis =?UTF-8?B?TG90aG9yw6k=?= , Thomas Petazzoni , netdev@vger.kernel.org, linux-stm32@st-md-mailman.stormreply.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH net-next 0/3] net: stmmac: Add support for coarse timestamping Message-ID: <20251015145519.280b6263@kmaincent-XPS-13-7390> In-Reply-To: <20251015102725.1297985-1-maxime.chevallier@bootlin.com> References: <20251015102725.1297985-1-maxime.chevallier@bootlin.com> Organization: bootlin X-Mailer: Claws Mail 4.2.0 (GTK 3.24.41; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-Last-TLS-Session-Version: TLSv1.3 On Wed, 15 Oct 2025 12:27:20 +0200 Maxime Chevallier wrote: > Hello everyone, >=20 > This is another attempt to support the fine vs coarse timestamping modes > in stmmac. >=20 > This mode allows trading off PTP clock frequency adjustment precision > versus timestamping precision. >=20 > In coarse mode, we lose the ability to fine-tune the PTP clock > frequency, but get better timestamping precision instead. This is > especially useful when acting as a PTP Grand Master, where the PTP clock > in sync'd to a high-precision GPS clock through PPS inputs. >=20 > This has been submitted before as a dedicated ioctl() back in 2020 [1]. > Since then, we now have a better representation of timestamp providers > with a dedicated qualifier (approx vs precise). >=20 > This series attempts to map these new qualifiers to stmmac's > timestamping modes, see patch 2 for details. >=20 > The main drawback IMO is that the qualifiers don't map very well to our > timestamping modes, as the "approx" qualifier actually maps to stmmac's > "coars" mode, but we actually gain in timestamping precision (while > losing frequency precision). https://elixir.bootlin.com/linux/v6.17.1/source/include/uapi/linux/net_tsta= mp.h#L16 "approx" was initially added for DMA timestamp point. Maybe we should add a new enum value here with a more suitable name. Regards, --=20 K=C3=B6ry Maincent, Bootlin Embedded Linux and kernel engineering https://bootlin.com