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 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 992ADC433FE for ; Wed, 20 Oct 2021 08:53:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 832F961004 for ; Wed, 20 Oct 2021 08:53:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230156AbhJTIzs convert rfc822-to-8bit (ORCPT ); Wed, 20 Oct 2021 04:55:48 -0400 Received: from relay11.mail.gandi.net ([217.70.178.231]:41621 "EHLO relay11.mail.gandi.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230125AbhJTIzq (ORCPT ); Wed, 20 Oct 2021 04:55:46 -0400 Received: (Authenticated sender: kory.maincent@bootlin.com) by relay11.mail.gandi.net (Postfix) with ESMTPSA id EA6EA100013; Wed, 20 Oct 2021 08:53:28 +0000 (UTC) Date: Wed, 20 Oct 2021 10:53:28 +0200 From: =?UTF-8?B?S8O2cnk=?= Maincent To: Geert Uytterhoeven Cc: Thomas Petazzoni , Andrew Lunn , netdev , Linux-Renesas , Linux Kernel Mailing List , Sergey Shtylyov , "David S. Miller" , Jakub Kicinski , Lad Prabhakar , Biju Das , Sergei Shtylyov , Adam Ford , Yoshihiro Shimoda , Yang Yingliang Subject: Re: [PATCH] net: renesas: Fix rgmii-id delays Message-ID: <20211020105328.411a712f@kmaincent-XPS-13-7390> In-Reply-To: References: <20211019145719.122751-1-kory.maincent@bootlin.com> <20211019173520.0154a8cb@kmaincent-XPS-13-7390> <20211019175746.11b388ce@windsurf> Organization: bootlin X-Mailer: Claws Mail 3.17.5 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello Geert, Thomas On Tue, 19 Oct 2021 22:05:41 +0200 Geert Uytterhoeven wrote: > Hi Thomas, > > On Tue, Oct 19, 2021 at 5:57 PM Thomas Petazzoni > wrote: > > On Tue, 19 Oct 2021 17:41:49 +0200 > > Andrew Lunn wrote: > > > > When people update the kernel version don't they update also the > > > > devicetree? > > > > > > DT is ABI. Driver writers should not break old blobs running on new > > > kernels. Often the DT blob is updated with the kernel, but it is not > > > required. It could be stored in a hard to reach place, shared with > > > u-boot etc. > > > > Right, but conversely if someone reads the DT bindings that exists > > today, specifies phy-mode = "rgmii-rxid" or phy-mmode = "rmgii-txid", > > Today == v5.10-rc1 and later? > > > this person will get incorrect behavior. Sure a behavior that is > > backward compatible with older DTs, but a terribly wrong one when you > > write a new DT and read the DT binding documentation. This is exactly > > the problem that happened to us. > > If you write a new DT, you read the DT binding documentation, and > "make dtbs_check" will inform you politely if you use the legacy/wrong > DT (i.e. lacking "[rt]x-internal-delay-ps")? Indeed this command will inform the missing required "[rt]x-internal-delay-ps". I am not use to that command, as it seems to check all the devicetree each time where I want only to check one. > > The current driver is backwards-compatible with the legacy/wrong DTB. > The current DT bindings (as of v5.10-rc1), using "[rt]x-internal-delay-ps" > are correct. > Or am I missing something here? You are correct. > > BTW, it's still not clear to me why the inversion would be needed. > Cfr. Andrew's comment: > > | So with rgmii-rxid, what is actually passed to the PHY? Is your > | problem you get twice the delay in one direction, and no delay in the > | other? Yes, it was the problem I got. The PHY I use have RX delay enabled by default, currently the PHY driver does not support delay configuration, therefore I let the MAC handle TX delay. I have stumbling over that legacy/wrong DTS on the old Kernel. Regards, Köry