From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752018AbeAYM3B (ORCPT ); Thu, 25 Jan 2018 07:29:01 -0500 Received: from mga14.intel.com ([192.55.52.115]:23719 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751707AbeAYM3A (ORCPT ); Thu, 25 Jan 2018 07:29:00 -0500 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.46,412,1511856000"; d="scan'208";a="25362064" Message-ID: <1516883334.7000.1252.camel@linux.intel.com> Subject: Re: [RFC] intel-lpss: remove .prepare() callback From: Andy Shevchenko To: Zhang Rui , linux-kernel@vger.kernel.org Cc: mika.westerberg@linux.intel.com, lee.jones@linaro.org Date: Thu, 25 Jan 2018 14:28:54 +0200 In-Reply-To: <1516867965-11124-1-git-send-email-rui.zhang@intel.com> References: <1516867965-11124-1-git-send-email-rui.zhang@intel.com> Organization: Intel Finland Oy Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.26.3-1 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2018-01-25 at 16:12 +0800, Zhang Rui wrote: > The .prepare() callback of intel-lpss driver does nothing but wakes up > its > children. I don't know if there is any reason to do so, but to me, > this is > not preferred because it should be the child device driver to do so > when > necessary, not the parent device driver. > Plus, .prepare() does not support asynchronization. > > For example, on MS Surface Pro 4, there are 4 intel-lpss devices which > are runtime suspended before system suspend, resuming each of them > takes > more than 100 milliseconds. Thus the .prepare() of intel-lpss driver > takes > 400ms+ on my surface pro 4, and I've seen platforms with 16 intel lpss > devices. > > With this patch applied, the child devices are resumed in the > .suspend() > stage of the child device, and they are done in parallel, thus only > 100ms > is needed, no matter how many intel lpss devices there are. > > I have tested it on three different platforms and didn't find any > obvious > problem caused by this patch, and it indeed reduces the suspend time a > lot. > @@ -482,17 +482,6 @@ static int resume_lpss_device(struct device *dev, > - device_for_each_child_reverse(dev, NULL, resume_lpss_device); Besides introduced compiler warning, did you check the latest linux-pm changes? commit 8425ec7faff005500aad89b9fc00e5ba91ac57b9 Author: Rafael J. Wysocki Date: Wed Jan 3 01:34:53 2018 +0100 PM / mfd: intel-lpss: Use DPM_FLAG_SMART_SUSPEND -- Andy Shevchenko Intel Finland Oy