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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id EABEECD5BD0 for ; Mon, 25 May 2026 12:28:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=rG5FSAIqm0gl60Kib+PBHlUScNgwLQMgHAfVV2AI5gQ=; b=lyZ7mQ1t1ZyuqwhXrJELqUXOHN aDBE+HtYuefdL/IR4LunMc3etkwNTB9Jt/5cCTb+3yOH5SDqAXPhTCiFbQvySdsfqE+QA+q7z8AFh COPRxF0Irw8qJztMtvD4N5t6G6vBRbnFl1lS9geCCgODkTYw5y00BDduKStzsr/s/WPCRRubdOPLq Xk70KPCwQRbF97oo7cbc1VBbEKhuwF85eSL9M4kWifE85kMDKLjmwpthfh9J4d7xPZ1VN2h7AS+hj YhCeHXw/wdoB606E6R/NuXSylo6Koci5Upo5qfDto2/IH6k77QkhF9kSy8n2Me5Wu41sLFFllQwwH uYIZAyRQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1wRUQB-0000000HBnJ-15uu; Mon, 25 May 2026 12:28:39 +0000 Received: from tor.source.kernel.org ([172.105.4.254]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1wRUQA-0000000HBn7-0sEp for linux-arm-kernel@lists.infradead.org; Mon, 25 May 2026 12:28:38 +0000 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id 47B29601FC; Mon, 25 May 2026 12:28:37 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id A7B1B1F00A3A; Mon, 25 May 2026 12:28:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1779712117; bh=rG5FSAIqm0gl60Kib+PBHlUScNgwLQMgHAfVV2AI5gQ=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=N4zc4RPZFO/rbuANzKKx7I46HlsqHS8Yv+8jr8VildSSNtdFex5zb/pCwqMDCo7rf FD/qAaevgeIZNz8vwkRHhgtEjCShBlYOx7mAN5JqUkBn1ahvnYQb4SEaMctG7BpC91 8C7EfQ7udA07EkKbQTcBNlnyRdJktiIRy5Fs4A4gfeg+RfdkFT5Fpm0ebSXa5m2NSi auxhxZLfp+/DNU7/iYdRi/hqWzeH9k9g92Ysw4WdZjoyUYNzbEynfQlgseeErCd+1f lKSMfQ3fXBnULPHqn0B4SxDlVBKQLLW5btQOpf77QKmEiQZYElc6TPmeV2ctUvHgtH 56cXvPgYUXxLQ== Message-ID: <8046287e-87a2-4d18-ad3d-248620a752a9@kernel.org> Date: Mon, 25 May 2026 14:28:32 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 2/5] dt-bindings: connector: Add fsl,io-connector binding To: "Chancel Liu (OSS)" , Frank Li Cc: Chancel Liu , "robh@kernel.org" , "krzk+dt@kernel.org" , "conor+dt@kernel.org" , "s.hauer@pengutronix.de" , "festevam@gmail.com" , "mturquette@baylibre.com" , "sboyd@kernel.org" , "kernel@pengutronix.de" , "devicetree@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "imx@lists.linux.dev" , "linux-arm-kernel@lists.infradead.org" , "linux-clk@vger.kernel.org" References: <20260509024846.2094049-1-chancel.liu@nxp.com> <20260509024846.2094049-3-chancel.liu@nxp.com> <20260515-resourceful-singing-roadrunner-ce25ec@quoll> <20260519-macho-degu-from-nibiru-960af2@quoll> <74eb56fb-546d-4b2c-9bbc-01a40937f5d3@kernel.org> From: Krzysztof Kozlowski Content-Language: en-US Autocrypt: addr=krzk@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 8bit X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 25/05/2026 08:26, Chancel Liu (OSS) wrote: >>>>>>>>>>> +description: >>>>>>>>>>> + The NXP I/O connector represents a physically present I/O >>>>>>>>>>> +connector on the >>>>>>>>>>> + base board. It acts as a nexus that exposes a constrained >>>>>>>>>>> +set >>>>>> of >>>>>>>>>>> +I/O >>>>>>>>>>> + resources, such as GPIOs, clocks, PWMs and interrupts, >>>>>>>>>>> +through fixed >>>>>>>>>>> + electrical wiring. All actual hardware providers reside on >>>>>>>>>>> +the >>>>>> base >>>>>>>> board. >>>>>>>>>>> + The connector node only defines index-based mappings to >>>>>>>>>>> + those >>>>>>>>>> providers. >>>>>>>>>>> + >>>>>>>>>>> +properties: >>>>>>>>>>> + compatible: >>>>>>>>>>> + const: fsl,io-connector >>>>>>>>>> >>>>>>>>>> Everything is IO. Everything is connector, so your compatible >>>>>>>>>> does not match requirements from writing bindings. >>>>>>>>>> >>>>>>>>> >>>>>>>>> Yes, this compatible is too generic. I will rename the >>>>>>>>> compatible to fsl,aud-io-connector. >>>>>>>> >>>>>>>> aud is not much better. Which boards have it? What's the pinout? >>>>>> What's >>>>>>>> standard? Is it described anywhere? If so, provide reference to >>>>>> spec/docs. >>>>>>>> >>>>>>> >>>>>>> This is not an industry standard electrical interface. This >>>>>>> connector >>>>>> >>>>>> Then if you do not have standard, then you have board specific >>>>>> layouts thus you need board-specific compatibles. You can use >>>>>> fallbacks. Generic fallback could work, but both io-connector and >>>>>> aud-io-connector are just too generic. Every connector is >>>>>> "connector" and "io", thus absolutely anything can be >>>>>> "io-connector". "aud" improves it only a bit, thus honestly I would >> go with board specific fallback as well. >>>>>> >>>>> >>>>> How about board specific + common fallback compatible like this: >>>>> compatible: >>>>> items: >>>>> - enum: >>>>> - fsl,imx95-19x19-evk-aud-io-connector >>>>> - fsl,imx952-evk-aud-io-connector >>>>> - const: fsl,imx-aud-io-connector Since the daughter board is >>>>> named “IMX-AUD-IO” in publicly available >>>> >>>> I don't think it is named like that. >>>> >>>> git grep -i imx-aud-io >>>> >>>>> documentation, common compatible clearly indicates that this >>>>> connector is intended for that. >>>>> >>>>> Also, I want to talk about the topic of generic connector. It's a >>>>> common design that daughter board is connected to base board through >>>>> a connector. This connector more often acts as a nexus that exposes >>>>> a constrained subset of GPIO, clock, PWM and interrupt resources to >>>>> the daughter board. Can we document this kind of connector as a >>>>> generic binding? >>>> >>>> So this binding is the connector between carrier and some addon? Then >>>> you don't get a compatible for that at all, because it is not >>>> necessary, not useful and NEVER used. Do you see socket LGA "connector" >> bindings? No. >>> >>> Not exactly. Any connector connects a carrier board with an add-on >> board. >>> The key point here is that this connector type is reused across >>> different boards, even though it is not an industry-standard >>> connector. Both the signal definitions and the mechanical layout are >> defined. >>> >>> The same add-on boards can therefore be reused across different base >>> boards that use this type of connector. >>> >>> There are also GPIO mappings involved. For example, pin 1 on the >>> connector may represent reset-gpios, but it could be connected to >>> GPIO0 on board A and GPIO1 on board B. >>> >>> Without a connector definition layer, this would create an N × M >>> combination problem. The Nexus node discussion already covered this >> topic: >>> https://osseu2025.sched.com/event/25Vrw >>> >>> An LGA socket is a CPU socket, where the signals are completely >>> transparent to software, so it is not a good comparison. A PCIe M.2 >>> Key-M/E connector would be a more appropriate comparison. >>> >> >> So the terminology of daughter and carrier boards was confusing. If this >> is a hat, mezzanine or other addon, it's fine. >> > > The IMX-AUD-IO is an add-on board that attaches to the base board. To > make it clearer, I will replace "daughter board" with "add-on board" > throughout descriptions. > >> I still insist on board specific compatibles - fallback and specific. >> > > The base board has a slot component that is mechanically compatible > with a PCIe x8 connector. However, it carries no PCIe signals and the > pins are repurposed to carry fixed board-level audio I/O related > signals. > > I think we can name a compatible reflects a standard mechanical form > factor. > For the compatibles (specific + fallback) I propose: > - enum: > - fsl,imx95-19x19-evk-aud-io-pcie-x8-slot > - fsl,imx952-evk-aud-io-pcie-x8-slot > - const: fsl,aud-io-pcie-x8-slot Does not solve my request, so I won't ack it. Maybe you will get ack from other DT maintainer then. Best regards, Krzysztof