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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7F7B9C433EF for ; Thu, 20 Jan 2022 18:02:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236470AbiATSCF (ORCPT ); Thu, 20 Jan 2022 13:02:05 -0500 Received: from ams.source.kernel.org ([145.40.68.75]:45772 "EHLO ams.source.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234621AbiATSCE (ORCPT ); Thu, 20 Jan 2022 13:02:04 -0500 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 54EF2B81E19; Thu, 20 Jan 2022 18:02:02 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 689BCC340E0; Thu, 20 Jan 2022 18:01:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1642701721; bh=xC8OW4CUchMp0erk9wqkXdiLHGoZ3LLIAA7sgkPWiP0=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=STqmId7/Gepb2e10OOESnjpCgVu+XYM9AIJ7eEWxDd3gFSyxf2LloLOmdjceOCH2u LmaFwZdvyDTJGVSiPASaMhJMInGt9tTb0JBz5T3pa+WS6Gde1JtMoVsQV+0u3+iVQ6 AS3azklGnlI9JEVw8iJ2uFK0R6c2d3ycMqNfGKKoDYcrB1XvwjROFX/qJ+vQxBeLe6 WQeI7glnlt9n6RBnoOT4D5T09IONYBTot49F3Xm241WTMRs2nLYNVZD3xBb96ENPD5 y/AXWhi1jmGqlxirgROQecJ9LlqNW3tBEkYhopkYNIjdEeTKlkFOsqVpLXHnJWIQPb iiva4lKWR1Wiw== Date: Thu, 20 Jan 2022 19:01:55 +0100 From: Marek =?UTF-8?B?QmVow7pu?= To: Marc Kleine-Budde Cc: Rob Herring , devicetree@vger.kernel.org, Vladimir Oltean , Holger Brunck , Andrew Lunn , "netdev@vger.kernel.org" , Russell King , linux-phy@lists.infradead.org, Vinod Koul , Kishon Vijay Abraham I , ore@pengutronix.de, alexandru.tachici@analog.com Subject: Re: [PATCH devicetree v3] dt-bindings: phy: Add `tx-p2p-microvolt` property binding Message-ID: <20220120190155.717f2d52@thinkpad> In-Reply-To: <20220120084914.ga7o372lyynbn4ly@pengutronix.de> References: <20220119131117.30245-1-kabel@kernel.org> <20220120084914.ga7o372lyynbn4ly@pengutronix.de> X-Mailer: Claws Mail 3.18.0 (GTK+ 2.24.33; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org On Thu, 20 Jan 2022 09:49:14 +0100 Marc Kleine-Budde wrote: > On 19.01.2022 14:11:17, Marek Beh=C3=BAn wrote: > > Common PHYs and network PCSes often have the possibility to specify > > peak-to-peak voltage on the differential pair - the default voltage > > sometimes needs to be changed for a particular board. > >=20 > > Add properties `tx-p2p-microvolt` and `tx-p2p-microvolt-names` for this > > purpose. The second property is needed to specify the mode for the > > corresponding voltage in the `tx-p2p-microvolt` property, if the voltage > > is to be used only for speficic mode. More voltage-mode pairs can be > > specified. > >=20 > > Example usage with only one voltage (it will be used for all supported > > PHY modes, the `tx-p2p-microvolt-names` property is not needed in this > > case): > >=20 > > tx-p2p-microvolt =3D <915000>; > >=20 > > Example usage with voltages for multiple modes: > >=20 > > tx-p2p-microvolt =3D <915000>, <1100000>, <1200000>; > > tx-p2p-microvolt-names =3D "2500base-x", "usb", "pcie"; > >=20 > > Add these properties into a separate file phy/transmit-amplitude.yaml, > > which should be referenced by any binding that uses it. =20 >=20 > If I understand your use-case correctly, you need different voltage p2p > levels in the connection between the Ethernet MAC and the Ethernet > switch or Ethernet-PHY? This is a SerDes differential pair amplitude. So yes to your question, if the MII interface uses differential pair, like sgmii, 10gbase-r, ... > Some of the two wire Ethernet standards (10base-T1S, 10base-T1L, > 100base-T1, 1000base-T1) defines several p2p voltage levels on the wire, > i.e. between the PHYs. Alexandru has posed a series where you can > specify the between-PHY voltage levels: >=20 > | https://lore.kernel.org/all/20211210110509.20970-8-alexandru.tachici@an= alog.com/ Copper ethernet is something different, so no conflict > Can we make clear that your binding specifies the voltage level on the > MII interface, in contrast Alexandru's binding? The binding explicitly says "common PHY", not ethernet PHY. I don't thing there will be any confusion. It can also be specified for USB3+ differential pairs, or PCIe differential pairs, or DisplayPort differential pairs... Marek