From patchwork Fri May 16 15:20:55 2014 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jacob Pan X-Patchwork-Id: 4193891 Return-Path: X-Original-To: patchwork-linux-pm@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.19.201]) by patchwork2.web.kernel.org (Postfix) with ESMTP id 207BDBFF02 for ; Fri, 16 May 2014 15:21:24 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 2F19220306 for ; Fri, 16 May 2014 15:21:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2345720270 for ; Fri, 16 May 2014 15:21:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932628AbaEPPVT (ORCPT ); Fri, 16 May 2014 11:21:19 -0400 Received: from mga02.intel.com ([134.134.136.20]:2772 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932291AbaEPPVS (ORCPT ); Fri, 16 May 2014 11:21:18 -0400 Received: from orsmga002.jf.intel.com ([10.7.209.21]) by orsmga101.jf.intel.com with ESMTP; 16 May 2014 08:21:18 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.97,1067,1389772800"; d="scan'208";a="541641770" Received: from ultegra.jf.intel.com (HELO ultegra) ([10.7.202.82]) by orsmga002.jf.intel.com with ESMTP; 16 May 2014 08:20:57 -0700 Date: Fri, 16 May 2014 08:20:55 -0700 From: Jacob Pan To: Alan Stern Cc: "Rafael J. Wysocki" , Linux PM list , ACPI Devel Maling List , Aaron Lu , Mika Westerberg , Linux Kernel Mailing List , Kevin Hilman , Ulf Hansson Subject: Re: [RFC][PATCH 2/3] PM / sleep: Mechanism to avoid resuming runtime-suspended devices unnecessarily Message-ID: <20140516082055.40cd2bb4@ultegra> In-Reply-To: References: <20140515000320.3c1c9256@jacob-desktop> Organization: OTC X-Mailer: Claws Mail 3.8.1 (GTK+ 2.24.17; x86_64-pc-linux-gnu) Mime-Version: 1.0 Sender: linux-pm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org X-Spam-Status: No, score=-7.5 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP On Thu, 15 May 2014 11:58:55 -0400 (EDT) Alan Stern wrote: > On Thu, 15 May 2014, Jacob Pan wrote: > > > On Thu, 15 May 2014 10:29:42 -0400 (EDT) > > Alan Stern wrote: > > > > > On Thu, 15 May 2014, Jacob Pan wrote: > > > > > > > > > should we respect ignore_children flag here? not all parent > > > > > > devices create children with proper .prepare() function. > > > > > > this allows parents override children. > > > > > > I am looking at USB, a USB device could have logical > > > > > > children such as ep_xx, they don't go through the same > > > > > > subsystem .prepare(). > > > > > > > > > > Well, I'm not sure about that. Let me consider that for a > > > > > while. > > > > OK. let me be more clear about the situation i see in USB. > > > > Correct me if I am wrong, a USB device will always has at least > > > > one endpoint/ep_00 as a kid for control pipe, it is a logical > > > > device. So when device_prepare() is called, its call back is > > > > NULL which makes .direct_complete = 0. Since children device > > > > suspend is called before parents, the parents .direct_complete > > > > flag will always get cleared. > > > > > > > > What i am trying to achieve here is to see if we avoid resuming > > > > built-in (hardwired connect_type) non-hub USB devices based on > > > > this new patchset. E.g. we don't want to resume/suspend USB > > > > camera every time in system suspend/resume cycle if they are > > > > already rpm suspended. We can save ~100ms resume time for the > > > > devices we have tested. > > > > > > This is a good point, but I don't think it is at all related to > > > ignore_children. > > > > > > Instead, it seems that the best way to solve it would be to add a > > > ->prepare() handler for usb_ep_device_type that would always turn > > > on direct_complete. > > > > > yeah, that would solve the problem with EP device type. But what > > about other subdevices. e.g. for USB camera, uvcvideo device? We > > can add .prepare(return 1;) for each level but would it be better > > to have a flag similar to ignore_children if not ignore_children > > itself. > > Something like that could always be added. or, how about if a device's .prepare() is NULL, we could assume .direct_resume() should be set. i.e. dev->power.direct_complete, info); > > > Actually, I don't understand why this is not related to > > ignore_children. Could you explain? > > It's hard to explain why two things are totally separate. Much > better for you to describe why you think they _are_ related, so that > I can explain how you are wrong. > > > If the parent knows it can ignore children and already rpm > > suspended, why do we still ask children? > > The "ignore_children" flag doesn't mean that the parent can ignore > its children. It means that the PM core is allowed to do a runtime > suspend of the parent while leaving the children at full power. > > In particular, it doesn't mean that the children's ->suspend() > callback will work correctly if it is called while the parent is > runtime suspended. that explains my question about ignore_chilren flag. thanks. > > Alan Stern > [Jacob Pan] --- To unsubscribe from this list: send the line "unsubscribe linux-pm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html --- a/drivers/base/power/main.c +++ b/drivers/base/power/main.c @@ -1539,7 +1539,7 @@ static int device_prepare(struct device *dev, pm_message_t state) pm_runtime_put(dev); return ret; } - dev->power.direct_complete = ret > 0 && state.event == PM_EVENT_SUSPEND + dev->power.direct_complete = (!callback || ret > 0) && state.event == PM_EVENT_SUSPEND && pm_runtime_suspended(dev); dev_dbg(dev, "%s:direct_complete %d, info %s\n", __func__,