From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from pandora.armlinux.org.uk (pandora.armlinux.org.uk [78.32.30.218]) (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 94D3627463; Mon, 21 Apr 2025 19:20:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=78.32.30.218 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1745263258; cv=none; b=mIv1G/zXOXcq8LUx7TTEsMz0Z2qrN+mi+HF8mX2fXgkZ1VPrsMOobWSsEfxDU39Q9u6MXbUWiAV0A1L0mYpnzfoZJHxkK/n2GFkA4EzCJQvRoVXLCHIvZDwdUWRTXDUGRToX2f4W5XphAQLdzhlAvQz3fbEcp+UjdRx6es8IHWs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1745263258; c=relaxed/simple; bh=FIgFzNnBr++vmjtDk8pCe3cYTsEPiaXPjORFzQs4bws=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=Rhdfod3r75r42uuog+mQjOWBu4DLgSogQsLLSKWDS8eSKTEbo2+61vaRi8PEJ4N2od7jOOJZat236vaqxz5bnNICwPtxhK86cYPC2WvIB884wLQLEzrsCti+VCO81mUi4hjKn5hDO8oFeoQ6g+X1W3lBSi4rLJg//LQftsZvmBY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=armlinux.org.uk; spf=none smtp.mailfrom=armlinux.org.uk; dkim=pass (2048-bit key) header.d=armlinux.org.uk header.i=@armlinux.org.uk header.b=JYRwM/jE; arc=none smtp.client-ip=78.32.30.218 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=armlinux.org.uk Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=armlinux.org.uk Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=armlinux.org.uk header.i=@armlinux.org.uk header.b="JYRwM/jE" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=armlinux.org.uk; s=pandora-2019; h=Sender:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=RBxdBp38IXRTVJ8jY24aTNAum3SlxGZFX20fKSQ3ODk=; b=JYRwM/jEdQoWgGqz6IdOEGv5e0 D/tDikDnrG0Zhs6L62dkRU3gpNIyQa5Sqn7jXvKICVVMX2FiKeVl8hrgfKNt3ivSdKTUjvpBpaYUp oJPbnMmr3MS/8wX/kBL9F7OafQgHlIjx/ey0huY5PAOPGA41R+mS+/zf0cnLfDxdTQhWqhnW6/7TS O2ei9BBeMgvKyeBHj44IIspAKGjekqp4k4aqAVcA18ljtzZbX61rFTzz0QFRpLYeDSdVHnTuqQxLc 9WUa3/qvqz8TLAiH3FQyEK4Jr3cX1Xeox3El7JzIOjKSa5iWn3BcuuVajsAIBnbyH8inmnyXZS2bc xUq6JpPA==; Received: from shell.armlinux.org.uk ([fd8f:7570:feb6:1:5054:ff:fe00:4ec]:50644) by pandora.armlinux.org.uk with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.96) (envelope-from ) id 1u6wh1-0003I5-1f; Mon, 21 Apr 2025 20:20:35 +0100 Received: from linux by shell.armlinux.org.uk with local (Exim 4.96) (envelope-from ) id 1u6wgw-0006hE-0M; Mon, 21 Apr 2025 20:20:30 +0100 Date: Mon, 21 Apr 2025 20:20:29 +0100 From: "Russell King (Oracle)" To: Matthias Schiffer Cc: Andrew Lunn , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Andy Whitcroft , Dwaipayan Ray , Lukas Bulwahn , Joe Perches , Jonathan Corbet , Nishanth Menon , Vignesh Raghavendra , Siddharth Vadapalli , Roger Quadros , Tero Kristo , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux@ew.tq-group.com Subject: Re: [PATCH net-next 1/4] dt-bindings: net: ethernet-controller: update descriptions of RGMII modes Message-ID: References: <218a27ae2b2ef2db53fdb3573b58229659db65f9.1744710099.git.matthias.schiffer@ew.tq-group.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <218a27ae2b2ef2db53fdb3573b58229659db65f9.1744710099.git.matthias.schiffer@ew.tq-group.com> Sender: Russell King (Oracle) On Tue, Apr 15, 2025 at 12:18:01PM +0200, Matthias Schiffer wrote: > diff --git a/Documentation/devicetree/bindings/net/ethernet-controller.yaml b/Documentation/devicetree/bindings/net/ethernet-controller.yaml > index 45819b2358002..2ddc1ce2439a6 100644 > --- a/Documentation/devicetree/bindings/net/ethernet-controller.yaml > +++ b/Documentation/devicetree/bindings/net/ethernet-controller.yaml > @@ -74,19 +74,21 @@ properties: > - rev-rmii > - moca > > - # RX and TX delays are added by the MAC when required > + # RX and TX delays are part of the board design (through PCB traces). MAC > + # and PHY must not add delays. > - rgmii > > - # RGMII with internal RX and TX delays provided by the PHY, > - # the MAC should not add the RX or TX delays in this case > + # RGMII with internal RX and TX delays provided by the MAC or PHY. No > + # delays are included in the board design; this is the most common case > + # in modern designs. > - rgmii-id > > - # RGMII with internal RX delay provided by the PHY, the MAC > - # should not add an RX delay in this case > + # RGMII with internal RX delay provided by the MAC or PHY. TX delay is > + # part of the board design. > - rgmii-rxid > > - # RGMII with internal TX delay provided by the PHY, the MAC > - # should not add an TX delay in this case > + # RGMII with internal TX delay provided by the MAC or PHY. RX delay is > + # part of the board design. > - rgmii-txid > - rtbi > - smii Sorry, but I don't think this wording improves the situation - in fact, I think it makes the whole thing way more confusing. Scenario 1: I'm a network device driver author. I read the above, Okay, I have a RGMII interface, but I need delays to be added. I'll detect when RGMII-ID is used, and cause the MAC driver to add the delays, but still pass PHY_INTERFACE_MODE_RGMII_ID to phylib. Scenario 2: I'm writing a DT file for a board. Hmm, so if I specify rgmii because the delays are implemented in the traces, but I need to fine-tune them. However, the documentation says that delays must not be added by the MAC or the PHY so how do I adjust them. I know, I'll use rgmii-id because that allows delays! I suspect neither of these two are really want you mean, but given this wording, that's exactly where it leads - which is more confusion and less proper understanding. -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTP is here! 80Mbps down 10Mbps up. Decent connectivity at last!