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 X-Spam-Level: X-Spam-Status: No, score=-2.5 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 12F10C432C3 for ; Thu, 14 Nov 2019 01:50:32 +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 2B7A0206D8 for ; Thu, 14 Nov 2019 01:50:32 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="O6CUejxg" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2B7A0206D8 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-riscv-bounces+infradead-linux-riscv=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=FbqMsjubqC5JE0D/ucsVRKcIV4fIm1CfdyoPKhFa7I0=; b=O6CUejxgvdc2qK O02LIKvVlxkPieulyTJQHCLnfMdjUGdv3nwKtDvVzJC34FuCZxBoi5ZMl3iBEyf1ZZrWLwyOnUaEH keH6kZc/WHQeAW/6qw5oKa1j9tMzP1kny6DBg+qcencckLIHzC+NAfTdq/H0zRFHB67VfP6vWdE45 dK4T2zwAGXNNoB/KoiC+w4Qn5Qe1NDVyM0mmutCXLqTm3f9ymMWFcbN+hEN3dYr/F2Izd3GwFjXZ7 YqyUuFfWWXcZjUVpP77XyjKAB7PzJmMFD1ju5eWlJVdHxFoFAO4rfp1cSJXAYRpYWEaPc/Q/xQKgf U0dM/lGvM0H/7/137nzA==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1iV4HH-0004g0-0x; Thu, 14 Nov 2019 01:50:31 +0000 Received: from mail-ot1-f68.google.com ([209.85.210.68]) by bombadil.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1iV4HD-0004fL-Sj for linux-riscv@lists.infradead.org; Thu, 14 Nov 2019 01:50:29 +0000 Received: by mail-ot1-f68.google.com with SMTP id w24so3002309otk.6 for ; Wed, 13 Nov 2019 17:50:27 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=9nyrjASHuxY3SmUh/9OWattAGU9yvQiMC8XCKQ9PU6E=; b=bwi7aaZhx6sgvKjGIW24LjFF274zJFQRDBuuPpv+LuQdJc5mhXX0I8GEUlF5W+ZP9Z z8ZGb4BarydUewgh9HEuHNH3Mm4df9JIFxGJPJL/CBQwm+Qy5Se9GpJGCW5gEKA4IUK/ vnZYJIOkXAVmZZ3J/471GoZ7tjct8ozHaWeLttX19ymhumdBek1lKE7yYz57dpANwA5N KKblATv0Kvr4vZwAiohfvQOlNF0sU/pBPYWw0Ybq17SfpVOvoCewG24bfevyfoowrD1M x8xIUu5ytaw+2D2LyuZAvA6u4HTZOdLEWBGE8KaBRYD+rxjqWxcymMrMnzxDZ0meWWBH rIsA== X-Gm-Message-State: APjAAAWY7hm0SePCgkvhXLvTyoIpSnMFvQmKghw6ieIp2N6dc3TabmdK F4aU2OhGfdl/Kf12yLroIw== X-Google-Smtp-Source: APXvYqxXDx1ryBh7LgzlyMuLqJ1JbZcffCwA8tUWrgTFQ29Fnfy0PdvhQizqi+lr/ix1eERF8bgUMQ== X-Received: by 2002:a9d:3675:: with SMTP id w108mr5840239otb.81.1573696226412; Wed, 13 Nov 2019 17:50:26 -0800 (PST) Received: from localhost (24-155-109-49.dyn.grandenetworks.net. [24.155.109.49]) by smtp.gmail.com with ESMTPSA id c20sm1327310otm.80.2019.11.13.17.50.25 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 13 Nov 2019 17:50:25 -0800 (PST) Date: Wed, 13 Nov 2019 19:50:25 -0600 From: Rob Herring To: Anup Patel Subject: Re: QEMU RISC-V virt machine poweroff driver Message-ID: <20191114015025.GB1748@bogus> References: <20191107212408.11857-1-hch@lst.de> <20191111161217.GA19157@lst.de> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20191113_175027_929150_0DFE57F9 X-CRM114-Status: GOOD ( 22.38 ) X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , devicetree@vger.kernel.org, Paul Walmsley , linux-pm@vger.kernel.org, Sebastian Reichel , Atish Patra , Palmer Dabbelt , Paul Walmsley , Alistair Francis , linux-riscv , Christoph Hellwig Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-riscv" Errors-To: linux-riscv-bounces+infradead-linux-riscv=archiver.kernel.org@lists.infradead.org On Tue, Nov 12, 2019 at 09:46:33AM +0530, Anup Patel wrote: > On Mon, Nov 11, 2019 at 10:50 PM Paul Walmsley wrote: > > > > On Mon, 11 Nov 2019, Christoph Hellwig wrote: > > > > > On Mon, Nov 11, 2019 at 05:06:24PM +0530, Anup Patel wrote: > > > > We really don't need this driver. Instead, we can simply re-use > > > > following drivers: > > > > mfd/syscon > > > > power/reset/syscon-reboot > > > > power/reset/syscon-poweroff > > > > > > > > Just enable following to your defconfig: > > > > CONFIG_POWER_RESET=y > > > > CONFIG_POWER_RESET_SYSCON=y > > > > CONFIG_POWER_RESET_SYSCON_POWEROFF=y > > > > CONFIG_SYSCON_REBOOT_MODE=y > > > > > > > > > > > > Once above drivers are enabled in your defconfig, make sure > > > > test device DT nodes are described in the following way for virt machine: > > > > > > Oh well, that is a lot more churn than a just works driver, and > > > will also pull it dependencies like regmap which quite blow up the > > > kernel size. But I guess that is where modern Linux drivers are > > > heading, so I'm not going to complain too loud.. > > > > The core issue is that putting random register writes in DT doesn't match > > the hardware. And the doctrine with DT has always been that it's supposed > > to represent the actual hardware. On FPGA bitstreams or ASICs that have > > the teststatus/testfinisher IP block, there really is an IP block out > > there - it's not just a bare register. > > > > If you update your driver to note that this is a SiFive IP block rather > > than a "RISC-V" IP block, I'll ack it. > > > > The SiFive Test device has only one register at offset 0x0 and three > possible magic values (0x3333, 0x5555, and 0x7777). > > The SYSCON based Reboot and Poweroff driver do exactly the same > thing what Christop's virt machine poweroff driver does so we are not > doing "random register writes" via DT. > > In fact, using SYSCON based Reboot and Poweroff we are actually > describing the Reboot and Poweroff mechanism directly in DT without > adding a complete driver for just one register write. This means we > are totally aligned with "DT doctrine" and over here we going one-step > more by describing Reboot and Poweroff mechanism in DT. > > A quick GREP shows that the SYSCON Reboot and Poweroff drivers > are quite widely used in ARM, ARM64 and MIPS architectures. Some of > the SOCs using these drivers are: Samsung Exynos, HiSilicon Hi3660, > HiSilicon Hi6220, Rockchip RK3xxx, AppliedMicro XGene, Broadcom > BCM33xx, Broadcom BCM63xx, etc. Majority of ARM/ARM64 SOCs > these days use the PSCI based SYSTEM RESET and SHUTDOWN > methods so we might not see more Reboot and Poweroff drivers for > ARM world. > > IMHO, we should definitely avoid adding a driver to Linux when there > a generic driver already available. This helps in kernel maintenance > in long-term. I guess I should have finished reading the thread... I agree with both of you. :) The DT binding should match the h/w as Paul says. However, a h/w specific binding can easily map to a generic driver if a given client OS has one. That probably hasn't been done yet for syscon-poweroff, but should. Rob _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv