From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <devicetree-owner@kernel.org>
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 5B53AC433F5
	for <linux-devicetree@archiver.kernel.org>; Thu, 24 Mar 2022 22:19:39 +0000 (UTC)
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S241989AbiCXWVK (ORCPT
        <rfc822;linux-devicetree@archiver.kernel.org>);
        Thu, 24 Mar 2022 18:21:10 -0400
Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33350 "EHLO
        lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S242692AbiCXWVJ (ORCPT
        <rfc822;devicetree@vger.kernel.org>); Thu, 24 Mar 2022 18:21:09 -0400
Received: from vps0.lunn.ch (vps0.lunn.ch [185.16.172.187])
        by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D43818FE61
        for <devicetree@vger.kernel.org>; Thu, 24 Mar 2022 15:19:35 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lunn.ch;
        s=20171124; h=In-Reply-To:Content-Disposition:Content-Type:MIME-Version:
        References:Message-ID:Subject:Cc:To:From:Date:From:Sender:Reply-To:Subject:
        Date:Message-ID:To:Cc:MIME-Version:Content-Type:Content-Transfer-Encoding:
        Content-ID:Content-Description:Content-Disposition:In-Reply-To:References;
        bh=uIfPofyuq9jXCiykRc3r/F358w9m2+gmmcJgChLDMcM=; b=djg9eGvYk/K0/p61r7PkgDJa72
        /o8Sai6SCbybHaem/4AvvP097eTdf15TxS8ktc63Nf1nSLvMbWbEfKgr0iWjP7hPtlyleOasmDUFO
        Trr2gi9oZ9WMov8BV0YEwrxyoOdM4DD4SynTuqOtLr/PErt+Ti2ttqTPeMkbd6beulcw=;
Received: from andrew by vps0.lunn.ch with local (Exim 4.94.2)
        (envelope-from <andrew@lunn.ch>)
        id 1nXVnj-00CVzH-84; Thu, 24 Mar 2022 23:19:27 +0100
Date:   Thu, 24 Mar 2022 23:19:27 +0100
From:   Andrew Lunn <andrew@lunn.ch>
To:     Jae Hyun Yoo <quic_jaehyoo@quicinc.com>
Cc:     Rob Herring <robh+dt@kernel.org>, Joel Stanley <joel@jms.id.au>,
        Andrew Jeffery <andrew@aj.id.au>,
        Jamie Iles <quic_jiles@quicinc.com>,
        Graeme Gregory <quic_ggregory@quicinc.com>,
        devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linux-aspeed@lists.ozlabs.org
Subject: Re: [PATCH] ARM: dts: aspeed: add Nuvia DC-SCM BMC
Message-ID: <Yjzub26okJosPkXC@lunn.ch>
References: <20220324164551.359570-1-quic_jaehyoo@quicinc.com>
 <YjzhT4gOJ9SKy6q+@lunn.ch>
 <88849423-c4a5-0a68-1900-72196395704e@quicinc.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <88849423-c4a5-0a68-1900-72196395704e@quicinc.com>
Precedence: bulk
List-ID: <devicetree.vger.kernel.org>
X-Mailing-List: devicetree@vger.kernel.org

On Thu, Mar 24, 2022 at 02:27:34PM -0700, Jae Hyun Yoo wrote:
> Hi Andrew,
> 
> On 3/24/2022 2:23 PM, Andrew Lunn wrote:
> > On Thu, Mar 24, 2022 at 09:45:51AM -0700, Jae Hyun Yoo wrote:
> > > From: Graeme Gregory <quic_ggregory@quicinc.com>
> > > 
> > > +&mac2 {
> > > +	status = "okay";
> > > +
> > > +	phy-mode = "rgmii";
> > 
> > Are you sure about this? That PHY are you using? It is more normal to
> > use rgmii-id.
> 
> Yes, I'm sure. PHY works with rgmii on my board. I picked a different
> clock delay setting too.

Do you know who is inserting the delay? It looks like rgmii will be
passed to the PHY. So there are few possibilities here:

The MAC is adding the delay. Not recommended, but does work. In that
case, your DT is correct.

The bootloader or strapping configures the PHY to insert the
delay. The PHY driver then ignores 'rgmii' and leaves the
configuration alone. This will break sometime in the future when
somebody fixes the PHY driver to actually set the PHY to rgmii as
requested. In this case, both the PHY driver and your DT is broken.

The board itself inserts the delays by having long tracks. In this
case, your DT is correct.

It would be good to understand this, just in case it is the second
condition.

      Andrew