From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from wnew3-smtp.messagingengine.com (wnew3-smtp.messagingengine.com [64.147.123.17]) (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 A7D9129CA for ; Tue, 28 Sep 2021 07:46:41 +0000 (UTC) Received: from compute2.internal (compute2.nyi.internal [10.202.2.42]) by mailnew.west.internal (Postfix) with ESMTP id 90F0F2B015A7; Tue, 28 Sep 2021 03:46:40 -0400 (EDT) Received: from mailfrontend2 ([10.202.2.163]) by compute2.internal (MEProxy); Tue, 28 Sep 2021 03:46:41 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sholland.org; h= to:cc:references:from:subject:message-id:date:mime-version :in-reply-to:content-type:content-transfer-encoding; s=fm3; bh=d tm6+SCKQFDhqHajeVv9mlgo//hwfhw0+BsVjCXiKJU=; b=gfWQKwKRnbVVOG5uT ZVsSIduZk65knrnWjTQ/i50fugQaOiTFwcSx+SD4h8dm2Xf/5dYP9tYM7QCIbcLj 6/DRPEPWfVKCifTBfv2j007+Nvrtx69bXAu+rd3Ietc4SqzBXVtP998v08uAnx4x 0pq3yWFc3QxJWq6W/MMtNv6+IuaXmpPGorIeDEDBhuUtDVZnZtW6t0L5hWCug6Vr MDtjQRekx4Y7e0+rruLdlRlO2heW/6zkcwfXJOaR67coAL0sf+xlBra2l3aQehJz AZayE6DDjHwAihcfzM2D+kIGel1B/spEDopSmrIRmtBvt4PpuixiCLto+L1LoKNA 4wQ5w== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=cc:content-transfer-encoding:content-type :date:from:in-reply-to:message-id:mime-version:references :subject:to:x-me-proxy:x-me-proxy:x-me-sender:x-me-sender :x-sasl-enc; s=fm3; bh=dtm6+SCKQFDhqHajeVv9mlgo//hwfhw0+BsVjCXiK JU=; b=r4wM3dhpzOGmjMQw05l+XvQucQK7ERRBNELDW4xNv5ooyZXkxYiUNKArX ypguFps/Kfw8hDkBfCgMIZA6UuHJGP9H/zz39nMO1mEmbyDkjSgPLeBNYWc8sGCg HhMGV4NG4FEWaZ6damMJU+PcwFDLLA/Fz13QIDVHJQu5d4CQHpNZ85Zo75ZmkjBR pziE1YV8T4hZRVFBmCerupDMSU0SBCx8JD2tIQL2GQDBgQ9xmJvSvILdAGhEfWvL cbAT3TyUSZlB/tVlYmYq9vhnO6CLbRChbwmEvQM4jtU2xW90TqySnthsIT2QvB/X zFrLw9k3msAQVDxnFEuQ0lU6zFnig== X-ME-Sender: X-ME-Received: X-ME-Proxy-Cause: gggruggvucftvghtrhhoucdtuddrgedvtddrudejledguddulecutefuodetggdotefrod ftvfcurfhrohhfihhlvgemucfhrghsthforghilhdpqfgfvfdpuffrtefokffrpgfnqfgh necuuegrihhlohhuthemuceftddtnecusecvtfgvtghiphhivghnthhsucdlqddutddtmd enucfjughrpefvfhfhuffkffgfgggjtgfgsehtkeertddtfeehnecuhfhrohhmpefurghm uhgvlhcujfholhhlrghnugcuoehsrghmuhgvlhesshhhohhllhgrnhgurdhorhhgqeenuc ggtffrrghtthgvrhhnpeehjeeghfdufeefteelieeggfehteevieetueffhefhffekuedv ffevffevtedufeenucevlhhushhtvghrufhiiigvpedtnecurfgrrhgrmhepmhgrihhlfh hrohhmpehsrghmuhgvlhesshhhohhllhgrnhgurdhorhhg X-ME-Proxy: Received: by mail.messagingengine.com (Postfix) with ESMTPA; Tue, 28 Sep 2021 03:46:39 -0400 (EDT) To: Maxime Ripard Cc: Chen-Yu Tsai , Jernej Skrabec , Rob Herring , Michael Turquette , Stephen Boyd , devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-clk@vger.kernel.org, linux-sunxi@lists.linux.dev, linux-kernel@vger.kernel.org References: <20210901053951.60952-1-samuel@sholland.org> <20210903145013.hn6dv7lfyvfys374@gilmour> <4a187add-462b-dfe4-868a-fdab85258b8d@sholland.org> <20210909084538.jeqltc7b3rtqvu4h@gilmour> From: Samuel Holland Subject: Re: [RFC PATCH 0/7] clk: sunxi-ng: Add a RTC CCU driver Message-ID: Date: Tue, 28 Sep 2021 02:46:39 -0500 User-Agent: Mozilla/5.0 (X11; Linux ppc64; rv:78.0) Gecko/20100101 Thunderbird/78.10.2 Precedence: bulk X-Mailing-List: linux-sunxi@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 In-Reply-To: <20210909084538.jeqltc7b3rtqvu4h@gilmour> Content-Type: text/plain; charset=windows-1252 Content-Language: en-US Content-Transfer-Encoding: 8bit On 9/9/21 3:45 AM, Maxime Ripard wrote: > On Fri, Sep 03, 2021 at 10:21:13AM -0500, Samuel Holland wrote: >> On 9/3/21 9:50 AM, Maxime Ripard wrote: >>> Hi, >>> >>> On Wed, Sep 01, 2021 at 12:39:44AM -0500, Samuel Holland wrote: >>>> This patch series adds a CCU driver for the RTC in the H616 and R329. >>>> The extra patches at the end of this series show how it would be >>>> explanded to additional hardware variants. >>>> >>>> The driver is intended to support the existing binding used for the H6, >>>> but also an updated binding which includes all RTC input clocks. I do >>>> not know how to best represent that binding -- that is a major reason >>>> why this series is an RFC. >>>> >>>> A future patch series could add functionality to the driver to manage >>>> IOSC calibration at boot and during suspend/resume. >>>> >>>> It may be possible to support all of these hardware variants in the >>>> existing RTC clock driver and avoid some duplicate code, but I'm >>>> concerned about the complexity there, without any of the CCU >>>> abstraction. >>>> >>>> This series is currently based on top of the other series I just sent >>>> (clk: sunxi-ng: Lifetime fixes and module support), but I can rebase it >>>> elsewhere. >>> >>> I'm generally ok with this, it makes sense to move it to sunxi-ng, >>> especially with that other series of yours. >>> >>> My main concern about this is the split driver approach. We used to have >>> that before in the RTC too, but it was mostly due to the early clock >>> requirements. With your previous work, that requirement is not there >>> anymore and we can just register it as a device just like the other >>> clock providers. >> >> That's a good point. Originally, I had this RTC CCU providing osc24M, so >> it did need to be an early provider. But with the current version, we >> could have the RTC platform driver call devm_sunxi_ccu_probe. That does >> seem cleaner. >> >> (Since it wasn't immediately obvious to me why this works: the only >> early provider remaining is the sun5i CCU, and it doesn't use the sun6i >> RTC driver.) >> >>> And since we can register all those clocks at device probe time, we >>> don't really need to split the driver in two (and especially in two >>> different places). The only obstacle to this after your previous series >>> is that we don't have of_sunxi_ccu_probe / devm_sunxi_ccu_probe >>> functions public, but that can easily be fixed by moving their >>> definition to include/linux/clk/sunxi-ng.h >> >> Where are you thinking the clock definitions would go? We don't export >> any of those structures (ccu_mux, ccu_common) or macros >> (SUNXI_CCU_GATE_DATA) in a public header either. > > Ah, right... > >> Would you want to export those? That seems like a lot of churn. Or would >> we put the CCU descriptions in drivers/clk/sunxi-ng and export a >> function that the RTC driver can call? (Or some other idea?) > > I guess we could export it. There's some fairly big headers in > include/linux/clk already (tegra and ti), it's not uAPI and we do have > reasons to do so, so I guess it's fine. > > I'd like to avoid having two drivers for the same device if possible, > especially in two separate places. This creates some confusion since the > general expectation is that there's only one driver per device. There's > also the fact that this could lead to subtle bugs since the probe order > is the link order (or module loading). I don't think there can be two "struct device"s for a single OF node. So if the CCU part is in drivers/clk/sunxi-ng, the CCU "probe" function would have to be called from the RTC driver. Since there has to be cooperation anyway, I don't think there would be any ordering problems. > And synchronizing access to registers between those two drivers will be > hard, while we could just share the same spin lock between the RTC and > clock drivers if they are instanciated in the same place. While the RTC driver currently shares a spinlock between the clock part and the RTC part, there isn't actually any overlap in register usage between the two. So there doesn't need to be any synchronization. Regards, Samuel 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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E56D3C433F5 for ; Tue, 28 Sep 2021 07:48:39 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id 9BE7260F4B for ; Tue, 28 Sep 2021 07:48:39 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 9BE7260F4B Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=sholland.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:Date: Message-ID:Subject:From:References:Cc:To:Reply-To:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Owner; 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Tue, 28 Sep 2021 03:46:39 -0400 (EDT) To: Maxime Ripard Cc: Chen-Yu Tsai , Jernej Skrabec , Rob Herring , Michael Turquette , Stephen Boyd , devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-clk@vger.kernel.org, linux-sunxi@lists.linux.dev, linux-kernel@vger.kernel.org References: <20210901053951.60952-1-samuel@sholland.org> <20210903145013.hn6dv7lfyvfys374@gilmour> <4a187add-462b-dfe4-868a-fdab85258b8d@sholland.org> <20210909084538.jeqltc7b3rtqvu4h@gilmour> From: Samuel Holland Subject: Re: [RFC PATCH 0/7] clk: sunxi-ng: Add a RTC CCU driver Message-ID: Date: Tue, 28 Sep 2021 02:46:39 -0500 User-Agent: Mozilla/5.0 (X11; Linux ppc64; rv:78.0) Gecko/20100101 Thunderbird/78.10.2 MIME-Version: 1.0 In-Reply-To: <20210909084538.jeqltc7b3rtqvu4h@gilmour> Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210928_004644_206908_3759932C X-CRM114-Status: GOOD ( 39.04 ) 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: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 9/9/21 3:45 AM, Maxime Ripard wrote: > On Fri, Sep 03, 2021 at 10:21:13AM -0500, Samuel Holland wrote: >> On 9/3/21 9:50 AM, Maxime Ripard wrote: >>> Hi, >>> >>> On Wed, Sep 01, 2021 at 12:39:44AM -0500, Samuel Holland wrote: >>>> This patch series adds a CCU driver for the RTC in the H616 and R329. >>>> The extra patches at the end of this series show how it would be >>>> explanded to additional hardware variants. >>>> >>>> The driver is intended to support the existing binding used for the H6, >>>> but also an updated binding which includes all RTC input clocks. I do >>>> not know how to best represent that binding -- that is a major reason >>>> why this series is an RFC. >>>> >>>> A future patch series could add functionality to the driver to manage >>>> IOSC calibration at boot and during suspend/resume. >>>> >>>> It may be possible to support all of these hardware variants in the >>>> existing RTC clock driver and avoid some duplicate code, but I'm >>>> concerned about the complexity there, without any of the CCU >>>> abstraction. >>>> >>>> This series is currently based on top of the other series I just sent >>>> (clk: sunxi-ng: Lifetime fixes and module support), but I can rebase it >>>> elsewhere. >>> >>> I'm generally ok with this, it makes sense to move it to sunxi-ng, >>> especially with that other series of yours. >>> >>> My main concern about this is the split driver approach. We used to have >>> that before in the RTC too, but it was mostly due to the early clock >>> requirements. With your previous work, that requirement is not there >>> anymore and we can just register it as a device just like the other >>> clock providers. >> >> That's a good point. Originally, I had this RTC CCU providing osc24M, so >> it did need to be an early provider. But with the current version, we >> could have the RTC platform driver call devm_sunxi_ccu_probe. That does >> seem cleaner. >> >> (Since it wasn't immediately obvious to me why this works: the only >> early provider remaining is the sun5i CCU, and it doesn't use the sun6i >> RTC driver.) >> >>> And since we can register all those clocks at device probe time, we >>> don't really need to split the driver in two (and especially in two >>> different places). The only obstacle to this after your previous series >>> is that we don't have of_sunxi_ccu_probe / devm_sunxi_ccu_probe >>> functions public, but that can easily be fixed by moving their >>> definition to include/linux/clk/sunxi-ng.h >> >> Where are you thinking the clock definitions would go? We don't export >> any of those structures (ccu_mux, ccu_common) or macros >> (SUNXI_CCU_GATE_DATA) in a public header either. > > Ah, right... > >> Would you want to export those? That seems like a lot of churn. Or would >> we put the CCU descriptions in drivers/clk/sunxi-ng and export a >> function that the RTC driver can call? (Or some other idea?) > > I guess we could export it. There's some fairly big headers in > include/linux/clk already (tegra and ti), it's not uAPI and we do have > reasons to do so, so I guess it's fine. > > I'd like to avoid having two drivers for the same device if possible, > especially in two separate places. This creates some confusion since the > general expectation is that there's only one driver per device. There's > also the fact that this could lead to subtle bugs since the probe order > is the link order (or module loading). I don't think there can be two "struct device"s for a single OF node. So if the CCU part is in drivers/clk/sunxi-ng, the CCU "probe" function would have to be called from the RTC driver. Since there has to be cooperation anyway, I don't think there would be any ordering problems. > And synchronizing access to registers between those two drivers will be > hard, while we could just share the same spin lock between the RTC and > clock drivers if they are instanciated in the same place. While the RTC driver currently shares a spinlock between the clock part and the RTC part, there isn't actually any overlap in register usage between the two. So there doesn't need to be any synchronization. Regards, Samuel _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel