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 008EBC3DA61 for ; Sat, 27 Jul 2024 11:26:20 +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-Type: Content-Transfer-Encoding:MIME-Version:References:In-Reply-To:Message-ID:Date :Subject:Cc:To:From:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=jJaK+Tq2MRyJGppTntlWWgs75XBmiF8pEgM2evEAVEE=; b=fLZaJxR0dxg/mxUmv3ZX95RSbz A2lZ3O921vNZ3xQdZRqxIaPSbnuqurHPdN0V+4UAcNCgn1RzPQdhkSl5UfwI6JK092k2Akwiaz8WY svcK2Aq/UEwfzbS93b1gCHkWtDtCrxhG8z/4Yugu9wZrvW/nmR7VG+afVyX+2gPkM65R2hTty5cb3 nsmdrZHEksVktqgAJ6O9U+ERyVlJ+NHHE8g19vFTo3ah2K/YUvslBzX9dzrua7bpSDByR4zWc4cGx puNwdXrFDAnsI+/OVvIWaeMqiYYtbiJWB7YkVraO7/r9J1PB7HSiZEl/j24ThxtYqiErcD+dUx0Il 1L067CTA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1sXfYs-00000006bhq-1kRN; Sat, 27 Jul 2024 11:26:06 +0000 Received: from gloria.sntech.de ([185.11.138.130]) by bombadil.infradead.org with esmtps (Exim 4.97.1 #2 (Red Hat Linux)) id 1sXfYR-00000006bda-2g1I; Sat, 27 Jul 2024 11:25:41 +0000 Received: from i5e860cde.versanet.de ([94.134.12.222] helo=diego.localnet) by gloria.sntech.de with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1sXfYK-0005ZZ-6A; Sat, 27 Jul 2024 13:25:32 +0200 From: Heiko =?ISO-8859-1?Q?St=FCbner?= To: Conor Dooley , Stephen Boyd Cc: mturquette@baylibre.com, robh@kernel.org, krzk+dt@kernel.org, conor+dt@kernel.org, linux-clk@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-rockchip@lists.infradead.org Subject: Re: [PATCH v2 1/3] dt-bindings: clocks: add binding for voltage-controlled-oscillators Date: Sat, 27 Jul 2024 13:25:31 +0200 Message-ID: <33119212.aRNtrjHk3s@diego> In-Reply-To: <00f9f4b8722d97b1c6fcec27d53bc06d.sboyd@kernel.org> References: <20240715110251.261844-1-heiko@sntech.de> <20240718-prozac-specks-6b5fd8b83e3e@spud> <00f9f4b8722d97b1c6fcec27d53bc06d.sboyd@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240727_042539_719330_CC4441F0 X-CRM114-Status: GOOD ( 32.92 ) 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 Am Samstag, 27. Juli 2024, 00:21:44 CEST schrieb Stephen Boyd: > Quoting Conor Dooley (2024-07-18 08:59:50) > > > > FWIW, I wouldn't classify this as device-specific. "enable-gpios" and > > "vdd-supply" are pretty generic and I think the latter is missing from > > the vast majority of real* "fixed-clocks". I would expect that devices > > where the datasheet would call > > > > * Real because there's plenty of "fixed-clocks" (both in and out of tree) > > that are used to work around the lack of a clock-controller driver for an > > SoC. > > I agree! > > > > > > I think generic power-sequences > > > were the topic back then, though that might have changed over time? > > > - There are places that describe "fixed-clock" as > > > "basic fixed-rate clock that cannot gate" [1] > > > > I think that that is something that could be changed, it's "just" a > > comment in some code! Sounds like Stephen disagrees though :) > > It's more about making a clear break from the fixed-clock binding so > that the extra properties are required. > > > > > > - Stephen also suggested a separate binding [2] > > > > I liked your "gated-oscillator" suggestion in another reply, but > > "gated-fixed-clock" might be a better "thematic" fit since this is a > > special case of fixed-clocks? > > > > It looks to me like we've arrived at the hardest problem in computer > science, i.e. naming. Any of these names is fine. I'd look to see what > those parts on mouser are called and use that to drive the compatible > name decision if you can't decide. The description section in the > binding could be verbose and link to some parts/pdfs if that helps too. > In the past I've seen EEs call these things clock buffers. I'm not a > classically trained EE myself but it usually helps to use similar names > from the schematic in DT because DT authors are sorta translating > schematics to DT. TL;DR: I'm fine with both "gated-oscillator" or "gated-fixed-clock" . Some tiny part in the back of my head wants to name things in the most specific way aka "gated-oscillator", but I guess "gated-fixed-clock" will possibly spare us the naming dance in the future :-) So I guess if nobody objects anymore, I'll go with "gated-fixed-clock". --------- 8< -------- Some background stuff for the oscillator / clock-buffer difference, which are actually both used on the Rock 5 ITX in question: [my ASCII-art may not survive mail readers] ------------ VCC3v3_PI6C (to both VDD + Enable) -----| VCC* | - CLKoutA - to PCIe | | | -------------------- | | - CLKoutB - to PCIe | 100MHz,3.3V,3225 |-------XTAL_IN_OUT -| Au5426 | -------------------- | | - REFout (unconnected) ------------ Just asking Google for that "100MHz,3.3V,3225" brings me to "100 MHz Standard Clock Oscillators" on Mouser. The Au5426 from Aurasemi is a "4 Differential and 1 LVCMOS Output Ultra Low Jitter High Performance Buffer" - aka a clock-buffer. In the Rock-5-ITX patch, I opted to ignore it, because on _that_ board it is transparent to the system, enabled by the same sources as the crystal and statically configured. On the other hand, the Au5426 actually _has_ input pins to select its working mode: - select between different clock sources - enable/disable the output of the input clock as refclk - configure the clock buffer type (lvpecl, lvds, hcsl, hiz) So I didn't want to conjure a binding for that stuff out of thin air :-) Heiko