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=-2.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham 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 5B969C04AA7 for ; Mon, 13 May 2019 15:00:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2E6732133F for ; Mon, 13 May 2019 15:00:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1557759649; bh=ILmhQ2QK/WxmPdkHQISBgY8FQ9Ydm+VpcAwCfLiiOd0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=bRdO6+qrerGTkRiQfUaT5TJprX7W6osnH2dNZenjN/p/7ZbyZjixb5aBHzve8a90M WM/F+YJWTxPgtv5wlHKTi7f9IXY7YDagk9atLkVHPySKbilQKISLp1ZceStl92R3Og z7eE1Mjolazl+iadFBlzR3l9G/DxlgnL/UCBdHxQ= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730553AbfEMPAs (ORCPT ); Mon, 13 May 2019 11:00:48 -0400 Received: from mga18.intel.com ([134.134.136.126]:42469 "EHLO mga18.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726738AbfEMPAs (ORCPT ); Mon, 13 May 2019 11:00:48 -0400 X-Amp-Result: UNSCANNABLE X-Amp-File-Uploaded: False Received: from orsmga006.jf.intel.com ([10.7.209.51]) by orsmga106.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 13 May 2019 08:00:47 -0700 X-ExtLoop1: 1 Received: from unknown (HELO localhost.localdomain) ([10.232.112.69]) by orsmga006.jf.intel.com with ESMTP; 13 May 2019 08:00:46 -0700 Date: Mon, 13 May 2019 08:55:24 -0600 From: Keith Busch To: Mario.Limonciello@dell.com Cc: hch@lst.de, keith.busch@intel.com, sagi@grimberg.me, linux-nvme@lists.infradead.org, rafael@kernel.org, linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, kai.heng.feng@canonical.com Subject: Re: [PATCH] nvme/pci: Use host managed power state for suspend Message-ID: <20190513145522.GA15421@localhost.localdomain> References: <20190510212937.11661-1-keith.busch@intel.com> <0080aaff18e5445dabca509d4113eca8@AUSX13MPC105.AMER.DELL.COM> <955722d8fc16425dbba0698c4806f8fd@AUSX13MPC105.AMER.DELL.COM> <20190513143741.GA25500@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.1 (2017-09-22) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, May 13, 2019 at 02:43:43PM +0000, Mario.Limonciello@dell.com wrote: > > Well, it sounds like your partners device does not work properly in this > > case. There is nothing in the NVMe spec that says queues should be > > torn down for deep power states, and that whole idea seems rather > > counter productive to low-latency suspend/resume cycles. > > Well I've got a thought, quoting the NVME spec: > "After a successful completion of a Set Features command for this feature, the controller shall be in the > Power State specified. If enabled, autonomous power state transitions continue to occur from the new state." > > If APST is enabled on this disk, what is to stop an autonomous reverse > transition from queue activity on the way down? Regardless of whether APST is enabled or not, the controller may autonomously transition out of a host requested low power state in response to host activity. Exiting a low power state should mean some other task is actively using the device, and if that's the case, why are you trying to enter a low power state in the first place? Alternatively, if host activity really is idle, then why is the device autonomously leaving the requested state?