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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 87698C46467 for ; Wed, 11 Jan 2023 05:25:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231231AbjAKFZM (ORCPT ); Wed, 11 Jan 2023 00:25:12 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59688 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231869AbjAKFYU (ORCPT ); Wed, 11 Jan 2023 00:24:20 -0500 Received: from verein.lst.de (verein.lst.de [213.95.11.211]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2A67FE032 for ; Tue, 10 Jan 2023 21:18:41 -0800 (PST) Received: by verein.lst.de (Postfix, from userid 2407) id 6AB6568BEB; Wed, 11 Jan 2023 06:18:36 +0100 (CET) Date: Wed, 11 Jan 2023 06:18:36 +0100 From: Christoph Hellwig To: Hector Martin Cc: Christoph Hellwig , Keith Busch , Jens Axboe , Sagi Grimberg , Eric Curtin , Janne Grunau , Sven Peter , Alyssa Rosenzweig , asahi@lists.linux.dev, linux-arm-kernel@lists.infradead.org, linux-nvme@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/2] nvme-apple: Do not try to shut down the controller twice Message-ID: <20230111051836.GA16576@lst.de> References: <20230111043614.27087-1-marcan@marcan.st> <20230111043614.27087-2-marcan@marcan.st> <20230111045402.GB15520@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.17 (2007-11-01) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jan 11, 2023 at 02:10:42PM +0900, Hector Martin wrote: > OK, so the first question is who is responsible for resetting the > controller after a shutdown? The spec requires a reset in order to bring > it back up from that state. Indeed the PCIe code does an explicit > disable right now (though, judging by the comment, it probably wasn't > done with the intent of resetting after a shutdown, it just happens to > work for that too :)) We need to do the reset before banging the registers to make sure the controller is in a sane state before starting to set it up. > Right now, apple_nvme_reset_work() tries to check for the condition of > an enabled controller (under the assumption that it's coming from a live > controller, not considering shutdown/sleep) and issue an > apple_nvme_disable(). However, this doesn't work when resuming because > at that point the firmware coprocessor is shut down, so the device isn't > usable (can't even get a disable command to complete properly). Perhaps > a better conditional here would be to check for > apple_rtkit_is_running(), since apple_nvme_disable() can't work otherwise. So on a resume the controller should have previously been shutdown properly, and this shouldn't be an issue. Does the apple implementation leave some weird state after a shut down? In that case the resume callback might want to do an explicit controller disable before doing the reset. > Alternatively, we could just revert to the prior behavior of always > issuing a disable after a shutdown. We need to disable at some point to > come back anyway, so it might as well be done early (before we shut down > firmware, so it works). So the disable before shutdown doesn't really make sense from the NVMe POV - the shutdown is to cleanly bring the device into a state where it can quickly recover. While a disable is an abprupt shutdown, which can have effects on recover time, and might also use way more P/E cycles than nessecary. So if you always want to do a disable, it should be after shutdown, and in doubt in the resume / setup path instead of the remove / suspend one.