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[2620:137:e000::1:20]) by mx.google.com with ESMTP id cr12-20020a170906d54c00b0078d2197d670si3789142ejc.661.2022.11.18.15.17.45; Fri, 18 Nov 2022 15:18:06 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; dkim=pass header.i=@ti.com header.s=ti-com-17Q1 header.b=qvIknZ4G; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=QUARANTINE sp=NONE dis=NONE) header.from=ti.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231483AbiKRWP4 (ORCPT + 90 others); Fri, 18 Nov 2022 17:15:56 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41788 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229925AbiKRWPx (ORCPT ); Fri, 18 Nov 2022 17:15:53 -0500 Received: from fllv0015.ext.ti.com (fllv0015.ext.ti.com [198.47.19.141]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B2763AF08A; Fri, 18 Nov 2022 14:15:52 -0800 (PST) Received: from lelv0265.itg.ti.com ([10.180.67.224]) by fllv0015.ext.ti.com (8.15.2/8.15.2) with ESMTP id 2AIMFY8G130971; Fri, 18 Nov 2022 16:15:34 -0600 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ti.com; s=ti-com-17Q1; t=1668809734; bh=YJ8Ee2BSlqS+12WdMmthz73OOuNqa7uireFaQ9RDJh4=; h=Date:From:To:CC:Subject:References:In-Reply-To; b=qvIknZ4Giqd8DsqWz9adUGPsGhTLDCmKOc3spxKPDwJqs1dOswNmMibD4cA7+3uzz lu2j/KMHtKHucEbxQMtRg2qffCGl1Le+/FKArEAE4DJ3FXtF7V9ZyDxRlJqa/F2lNK +vXkJuDheccCGeL4kIAO478l16RKSMthg44Bddiw= Received: from DFLE102.ent.ti.com (dfle102.ent.ti.com [10.64.6.23]) by lelv0265.itg.ti.com (8.15.2/8.15.2) with ESMTPS id 2AIMFYWW025451 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=FAIL); Fri, 18 Nov 2022 16:15:34 -0600 Received: from DFLE103.ent.ti.com (10.64.6.24) by DFLE102.ent.ti.com (10.64.6.23) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.2507.16; Fri, 18 Nov 2022 16:15:34 -0600 Received: from fllv0039.itg.ti.com (10.64.41.19) by DFLE103.ent.ti.com (10.64.6.24) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.2507.16 via Frontend Transport; Fri, 18 Nov 2022 16:15:34 -0600 Received: from localhost (ileaxei01-snat2.itg.ti.com [10.180.69.6]) by fllv0039.itg.ti.com (8.15.2/8.15.2) with ESMTP id 2AIMFYsY071765; Fri, 18 Nov 2022 16:15:34 -0600 Date: Fri, 18 Nov 2022 16:15:34 -0600 From: Nishanth Menon To: Andrew Davis CC: Apurva Nandan , Vignesh Raghavendra , Tero Kristo , Rob Herring , Krzysztof Kozlowski , Linus Walleij , , , , , Hari Nagalla Subject: Re: [PATCH v3 4/4] arm64: dts: ti: Add support for J784S4 EVM board Message-ID: <20221118221534.52rfyf5gsck3xrrb@sauciness> References: <20221116130428.161329-1-a-nandan@ti.com> <20221116130428.161329-5-a-nandan@ti.com> <20221118174754.y37pq77drvla2uxj@tinderbox> <8c123fa2-caab-d2dd-5eb4-688f1c6abb33@ti.com> <20221118180808.wnel7d6gswsnooww@junkman> <93242211-95e7-09a0-fced-5ef2deb9fc08@ti.com> <20221118192744.wish2vrxgy7dg7c2@unnerving> <3d5e41f6-16a8-4298-ccd3-6db60f94eb47@ti.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <3d5e41f6-16a8-4298-ccd3-6db60f94eb47@ti.com> User-Agent: NeoMutt/20171215 X-EXCLAIMER-MD-CONFIG: e1e8a2fd-e40a-4ac6-ac9b-f7e9cc9ee180 X-Spam-Status: No, score=-4.4 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_MED, SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 15:08-20221118, Andrew Davis wrote: > On 11/18/22 1:27 PM, Nishanth Menon wrote: > > On 12:15-20221118, Andrew Davis wrote: > > > I don't see either of those addressed in that thread, only that > > > the aliases should go in the .dts files and be trimmed, nothing > > > > Key is trimmed to what the system and ecosystem needs. > > > > > stops us from: > > > > > > chosen { > > > stdout-path = "serial10:115200n8"; > > > }; > > > > > > aliases { > > > serial10 = &main_uart8; > > > }; > > > > Do we need 10 serial aliases? There are'nt 10 serial ports exposed in > > j782s2. ok - lets say we do this, then: [1] is needed to boot? but why > > do we need to do that for all armv8 platforms when aliases allows us > > Why do we need SERIAL_8250_NR_UARTS at all, might be a better question. > These should be dynamically allocated if the number goes over the > default count imposed by the TTY framework. Maybe folks are still a > bit too afraid to touch the TTY subsystem core, I don't blame them.. > > > to trim it to just the 3 or 4 serial ports the platform really needs > > That + being able to use the convention that serial2 is always linux > > console, is'nt that a good thing? Hence recommending to just expose the > > serialports as aliases to exactly what we need while keeping serial2 as > > the linux console (which in this case happens to be main_uart8 - example > > as j721s2 does). > > > > "serial2 as the linux console" is *not* a convention, we just don't want to > fix up our bootloader/userspace to actually reason about what serial ports to > put logins on. Why not make ttyS10 the default, or ttyS666, it doesn't solve > your multi-distro issue either way since they usually only start a login on > ttyS0, console=, and/or the first virtual tty. Never on ttyS2. So you are > hacking up DT for a solution that doesn't do what you want in the end. ttyS2 is an accidental convention not a "by design" or definition convention. I suspect we ended up here from old OMAP days - all platforms in k3 ended up with ttyS2. In hindsight, if I had to do it by design, I would probably have picked ttyS0, well, we did'nt. $ git grep stdout-path arch/arm/boot/dts|grep serial|cut -d '=' -f 2|cut -d ':' -f1|grep -v '&'|sort|uniq -c 379 "serial0 21 "serial1 33 "serial2 13 "serial3 1 "/slaves@3e000000/serial@0 $ git grep stdout-path arch/arm64/boot/dts|grep serial|cut -d '=' -f 2|cut -d ':' -f1|grep -v '&'|sort|uniq -c 245 "serial0 17 "serial0"; 7 "serial1 49 "serial2 3 "serial3 2 "serial4 2 "serial5 2 "serial6 $ git grep stdout-path arch/arm64/boot/dts/ti|grep serial|cut -d '=' -f 2|cut -d ':' -f1|grep -v '&'|sort|uniq -c 8 "serial2 1 "serial3 I don't buy the argument here for 1-1 mapping of aliased serial instances to instances - why should main_uart8 be ttyS10, why not ttyS8 (it is equally valid - why was it called uart8?).. That mapping is just a convention we are choosing to create. The iot2050 ecosystem picked ttyS3 as the linux console for reasons of that ecosystem. K3 so far has selected ttyS2 as the convention for console - no matter where the serial instances have been located. I want to maintain consistency of existing TI platforms here without needing to shove a dozen things on existing users (yes j78-evm is a new board, but it is within the existing k3 s/w ecosystem and yes, getty, systemd etc are smarter today than once upon a time) So, given TI K3 history does'nt follow rest of the non-TI instances unfortunately - and I am going to put my foot down here - serial8 or 10 is "fake" anyways - rationalization can be made in different ways. So pushing for one over the other is not something I will entertain. From usage model point of view - serial0 will be the best candidate as console followed by serial2 (purely statistically speaking). In K3 context, it is just serial2 in TI board ecosystem. That is a discussion for pros and cons - Open to hearing opinions. Unless I hear 1000% strong reasons with _backing data_ - not an subjective "it is correct thing to do" - why we'd want to move TI board ecosystem (including all the pains of bootloader combinations etc) switch over to ttyS0[1], having a mix and churn for the s/w ecosystem of having to deal with ttyS0 and ttyS2 nodes in arm64/dts/ti at least for the TI board ecosystem.. I cant see why i want to put the ecosystem through another churn on consoles.. But, fine, i will keep my ears open. If there are no strong arguments with _data_, then we stick with serial2 and y'all can curse me for another decade+ for that call :) [1] I have'nt forgotten ttyO2 to ttyS2 transition of OMAP https://duckduckgo.com/?q=ttyO2+to+ttyS2+omap -- Regards, Nishanth Menon Key (0xDDB5849D1736249D) / Fingerprint: F8A2 8693 54EB 8232 17A3 1A34 DDB5 849D 1736 249D