From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.9 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2DC7FC4BA0B for ; Wed, 26 Feb 2020 11:30:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 03A8B20637 for ; Wed, 26 Feb 2020 11:30:54 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=walle.cc header.i=@walle.cc header.b="v9g1y9D2" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728259AbgBZLaw (ORCPT ); Wed, 26 Feb 2020 06:30:52 -0500 Received: from ssl.serverraum.org ([176.9.125.105]:38915 "EHLO ssl.serverraum.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728072AbgBZLav (ORCPT ); Wed, 26 Feb 2020 06:30:51 -0500 Received: from ssl.serverraum.org (web.serverraum.org [172.16.0.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ssl.serverraum.org (Postfix) with ESMTPSA id 8168422EEB; Wed, 26 Feb 2020 12:30:48 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=walle.cc; s=mail2016061301; t=1582716648; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=49vbSdUeTzuDFAZGKG9960moA+ZZ59VpBj1mcCy3Iks=; b=v9g1y9D2DjSGnHgOFwe/gfIfxqbCUZnb9GGeHyk8oUoqdZ7Zd1Ya5xLA3YZuyaqscKbIEa 83mVa1jXsSJbWmK9rQzHcjEHHHveei0eiQU2241q6jM2xl6hiAQDnBAFU2Lr3zuww0dr2j ZBPz2sx0mw5H6CAvQ/DfbVUfRWRCn9g= MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Date: Wed, 26 Feb 2020 12:30:48 +0100 From: Michael Walle To: Richard Cochran Cc: Andrew Lunn , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Florian Fainelli , Heiner Kallweit , Russell King , "David S . Miller" Subject: Re: [RFC PATCH 0/2] AT8031 PHY timestamping support In-Reply-To: <20200226025441.GB10271@localhost> References: <20200225230819.7325-1-michael@walle.cc> <20200225235040.GF9749@lunn.ch> <9955C44A-8105-4087-8555-BAC5AE4AF25D@walle.cc> <20200226025441.GB10271@localhost> Message-ID: X-Sender: michael@walle.cc User-Agent: Roundcube Webmail/1.3.10 X-Spamd-Bar: + X-Rspamd-Server: web X-Rspamd-Queue-Id: 8168422EEB X-Spamd-Result: default: False [1.40 / 15.00]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; FREEMAIL_ENVRCPT(0.00)[gmail.com]; TO_MATCH_ENVRCPT_ALL(0.00)[]; TAGGED_RCPT(0.00)[]; MIME_GOOD(-0.10)[text/plain]; DKIM_SIGNED(0.00)[]; RCPT_COUNT_SEVEN(0.00)[8]; NEURAL_HAM(-0.00)[-0.424]; FREEMAIL_TO(0.00)[gmail.com]; RCVD_COUNT_ZERO(0.00)[0]; FROM_EQ_ENVFROM(0.00)[]; MIME_TRACE(0.00)[0:+]; FREEMAIL_CC(0.00)[lunn.ch,vger.kernel.org,gmail.com,armlinux.org.uk,davemloft.net]; MID_RHS_MATCH_FROM(0.00)[]; SUSPICIOUS_RECIPS(1.50)[] Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Am 2020-02-26 03:54, schrieb Richard Cochran: > On Wed, Feb 26, 2020 at 01:07:26AM +0100, Michael Walle wrote: >> Am 26. Februar 2020 00:50:40 MEZ schrieb Andrew Lunn : >> >That sounds fundamentally broken. > > Right. It can't work unless the PHY latches the time stamp. To make things worse, it only has one slot for RX and one slot for TX timestamps. >> This might be the case, but the datasheet (some older revision can >> be found on the internet, maybe you find something) doesn't mention >> it. Nor does the PTP "guide" (I don't know the exact name, I'd have >> to check at work) of this PHY. Besides the timestamp there's also >> the sequence number and the source port id which would need to be >> read atomically together with the timestamp. > > Maybe the part is not intended to be used at all in this way? > > AFAICT, PHYs like this are meant to feed a "PTP frame detected" pulse > into the time stamping unit on the attached MAC. The interrupt serves > to allow the SW to gather the matching fields from the frame. But then there would need to be such a hardware pin, correct? Unless you'd misuse the INT# for it. Also, why should the PHY then have a PHC which can be adjusted. >> That sounds fundamentally broken. Which would be odd. Sometimes there >> is a way to take a snapshot of the value. Reading the first word could >> trigger this snapshot. Or the last word, or some status register. One >> would hope the datasheet would talk about this. > > This might be the case, but the datasheet (some older revision can > be found on the internet, maybe you find something) doesn't mention > it. Nor does the PTP "guide" (I don't know the exact name, I'd have > to check at work). BTW, the name of the document is "AR8031 1588v2 Precision Time Protocol, Application Note, 80-Y0618-15 Rev. A", which describes a use case where the RTC (ie PHC) is in the AR8031. I don't argue that the PHY is not broken, only that Atheros at least intended to have that use case. -michael