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=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,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 8844AC433DF for ; Mon, 29 Jun 2020 19:09:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 67B85206E2 for ; Mon, 29 Jun 2020 19:09:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730912AbgF2TJk (ORCPT ); Mon, 29 Jun 2020 15:09:40 -0400 Received: from comms.puri.sm ([159.203.221.185]:42786 "EHLO comms.puri.sm" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730752AbgF2TJb (ORCPT ); Mon, 29 Jun 2020 15:09:31 -0400 Received: from localhost (localhost [127.0.0.1]) by comms.puri.sm (Postfix) with ESMTP id D1311DFFEA; Mon, 29 Jun 2020 02:43:03 -0700 (PDT) Received: from comms.puri.sm ([127.0.0.1]) by localhost (comms.puri.sm [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 6AjvMKkxQc8S; Mon, 29 Jun 2020 02:43:03 -0700 (PDT) Subject: Re: [PATCH] scsi: sd: add runtime pm to open / release To: Alan Stern , Bart Van Assche Cc: jejb@linux.ibm.com, Can Guo , martin.petersen@oracle.com, linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org, kernel@puri.sm References: <20200623111018.31954-1-martin.kepplinger@puri.sm> <1379e21d-c51a-3710-e185-c2d7a9681fb7@acm.org> <20200626154441.GA296771@rowland.harvard.edu> From: Martin Kepplinger Autocrypt: addr=martin.kepplinger@puri.sm; keydata= mQINBFULfZABEADRxJqDOYAHfrp1w8Egcv88qoru37k1x0Ugy8S6qYtKLAAt7boZW+q5gPv3 Sj2KjfkWA7gotXpASN21OIfE/puKGwhDLAySY1DGNMQ0gIVakUO0ji5GJPjeB9JlmN5hbA87 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enabling runtime PM in sysfs (again, >>> because sd_probe() calls autopm_put() and thus allows it: >>> >>> [ 27.384446] sd 0:0:0:0: scsi_runtime_suspend >>> [ 27.432282] blk_pre_runtime_suspend >>> [ 27.435783] sd_suspend_common >>> [ 27.438782] blk_post_runtime_suspend >>> [ 27.442427] scsi target0:0:0: scsi_runtime_suspend >>> [ 27.447303] scsi host0: scsi_runtime_suspend >>> >>> then I "mount /dev/sda1 /mnt" and none of the resume() functions get >>> called. To me it looks like the sd driver should initiate resuming, and >>> that's not implemented. >>> >>> what am I doing wrong or overlooking? how exactly does (or should) the >>> block layer initiate resume here? >> >> As far as I know runtime power management support in the sd driver is working >> fine and is being used intensively by the UFS driver. The following commit was >> submitted to fix a bug encountered by an UFS developer: 05d18ae1cc8a ("scsi: >> pm: Balance pm_only counter of request queue during system resume") # v5.7. > > I just looked at that commit for the first time. > > Instead of making the SCSI driver do the work of deciding what routine to > call, why not redefine blk_set_runtime_active(q) to simply call > blk_post_runtime_resume(q, 0)? Or vice versa: if err == 0 have > blk_post_runtime_resume call blk_set_runtime_active? > > After all, the two routines do almost the same thing -- and the bug > addressed by this commit was caused by the difference in their behaviors. > > If the device was already runtime-active during the system suspend, doing > an extra clear of the pm_only counter won't hurt anything. > >> I'm not sure which bug is causing trouble on your setup but I think it's likely >> that the root cause is somewhere else than in the block layer, the SCSI core >> or the SCSI sd driver. >> >> Bart. > > Martin's best approach would be to add some debugging code to find out why > blk_queue_enter() isn't calling bkl_pm_request_resume(), or why that call > doesn't lead to pm_request_resume(). > > Alan Stern > Hi Alan, blk_queue_enter() always - especially when sd is runtime suspended and I try to mount as above - sets success to be true for me, so never continues down to bkl_pm_request_resume(). All I see is "PM: Removing info for No Bus:sda1". thanks, martin