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=-12.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable 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 4AFD8C433B4 for ; Mon, 10 May 2021 03:39:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 03C7061464 for ; Mon, 10 May 2021 03:39:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230181AbhEJDkk (ORCPT ); Sun, 9 May 2021 23:40:40 -0400 Received: from wout3-smtp.messagingengine.com ([64.147.123.19]:34933 "EHLO wout3-smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230126AbhEJDkj (ORCPT ); Sun, 9 May 2021 23:40:39 -0400 Received: from compute1.internal (compute1.nyi.internal [10.202.2.41]) by mailout.west.internal (Postfix) with ESMTP id 50D4917C4; Sun, 9 May 2021 23:39:33 -0400 (EDT) Received: from mailfrontend1 ([10.202.2.162]) by compute1.internal (MEProxy); Sun, 09 May 2021 23:39:33 -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=fm2; bh=I ZUFszC6jE/mtDj0KCiCRll83jCHjDqxXjCZzLBuhwU=; b=lapYcN9ptLh86Cscs MMQRNm8UYK3+e08/ShU/GX1v1v9lBEMi3Cew5KOAhtIfOQHzebOdqVUJugyIayKt 1tV2H1om0IFFvBuH5WKWgZedJw//3R/PqD3g6fJJcgHjoYc3IxdbT22in1BM7/6u Q8+plX63zDvHKOr1ycqVQy+xB1cTyvt2jun1klGiP1y55PqsjannHnvb/dM6oKX+ G1j2OhwN65Z5xeeKRorHRGRdfQ0a6KZUaZsOYpeS3jimJ6x92FQyI3sLQDH1H1YN eoSacoJuDzJBmd8yYpvhq8E2pdT10ounLChSE7tbyfZ+rtDwIF+d+STSjWgd1JRv UaVkg== 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=fm2; bh=IZUFszC6jE/mtDj0KCiCRll83jCHjDqxXjCZzLBuh wU=; b=msGzqQU1RGw9+1Txytj0DVNTIs4+ucYxyiQh0ajyDCR1VVX2NNvk8AEsf SsoRqMAq79NEvpah5BMJz3COnMo0JtsUe8G7KWofRBP4OcLfG+asv0LFFLFb8NAB aT9VThGcrs777j2N5acJp9T1YH7jC78rKplrVcE+/4QfxL1I7ry+JyAbf6rqgYF9 tdAlHZ+Qa6IAh+bjilqKsw61jkuZB52g2cGuk3yjPdPZk8JmbcXAthkYzJg+MyAf wNsjhkvqQaf6Q7D4DUJlZ5wVkBmkKGO7Zv63kcf7YfCjFlu834Q2dvkMVyYVxfXH 4hIhHNZkzDvtSbcuPjxGTDyN2D8XQ== X-ME-Sender: X-ME-Proxy-Cause: gggruggvucftvghtrhhoucdtuddrgeduledrvdegjedgjeduucetufdoteggodetrfdotf fvucfrrhhofhhilhgvmecuhfgrshhtofgrihhlpdfqfgfvpdfurfetoffkrfgpnffqhgen uceurghilhhouhhtmecufedttdenucesvcftvggtihhpihgvnhhtshculddquddttddmne cujfgurhepvfhfhffukffffgggjggtgfesthekredttdefheenucfhrhhomhepufgrmhhu vghlucfjohhllhgrnhguuceoshgrmhhuvghlsehshhholhhlrghnugdrohhrgheqnecugg ftrfgrthhtvghrnhepheejgefhudeffeetleeigefgheetveeiteeuffehhfffkeeuvdff veffveetudefnecukfhppeejtddrudefhedrudegkedrudehudenucevlhhushhtvghruf hiiigvpedtnecurfgrrhgrmhepmhgrihhlfhhrohhmpehsrghmuhgvlhesshhhohhllhgr nhgurdhorhhg X-ME-Proxy: Received: from [70.135.148.151] (70-135-148-151.lightspeed.stlsmo.sbcglobal.net [70.135.148.151]) by mail.messagingengine.com (Postfix) with ESMTPA; Sun, 9 May 2021 23:39:31 -0400 (EDT) To: Maxime Ripard Cc: Alessandro Zummo , Alexandre Belloni , Chen-Yu Tsai , Jernej Skrabec , linux-rtc@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-sunxi@lists.linux.dev, linux-kernel@vger.kernel.org References: <20210419014549.26900-1-samuel@sholland.org> <20210430090206.lybmygrt636nysoc@gilmour> From: Samuel Holland Subject: Re: [PATCH] rtc: sun6i: Add NVMEM provider Message-ID: Date: Sun, 9 May 2021 22:39:30 -0500 User-Agent: Mozilla/5.0 (X11; Linux ppc64; rv:78.0) Gecko/20100101 Thunderbird/78.10.0 MIME-Version: 1.0 In-Reply-To: <20210430090206.lybmygrt636nysoc@gilmour> Content-Type: text/plain; charset=windows-1252 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 4/30/21 4:02 AM, Maxime Ripard wrote: > Hi, > > On Sun, Apr 18, 2021 at 08:45:49PM -0500, Samuel Holland wrote: >> The sun6i RTC provides 32 bytes of general-purpose data registers. >> They can be used to save data in the always-on RTC power domain. >> The registers are writable via 32-bit MMIO accesses only. >> >> Expose the region as a NVMEM provider so it can be used by userspace and >> other drivers. >> >> Signed-off-by: Samuel Holland > > As far as I understood, you want to use those registers to implement > super-standby? If so, while it makes sense for the kernel to be able to > be able to write to those registers, I guess it would be a bit unwise to > allow the userspace to access it? I want the user to be able to pass information to the bootloader (to select a boot device, e.g. reboot to FEL). I also want the user to be able to read data stored to these registers by system firmware (e.g. crust writes exception information there). It's not really related to standby. I would want to stack a nvmem-reboot-mode on top to give friendlier names to some of the numbers, but I don't see a problem with root having direct access to the registers. It's no different from /dev/nvram providing access to the PC CMOS RAM. Regards, Samuel