From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933276AbcBAPPc (ORCPT ); Mon, 1 Feb 2016 10:15:32 -0500 Received: from mga11.intel.com ([192.55.52.93]:5058 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932750AbcBAPP3 (ORCPT ); Mon, 1 Feb 2016 10:15:29 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.22,380,1449561600"; d="scan'208";a="645199312" Message-ID: <1454339763.32507.26.camel@linux.intel.com> Subject: Re: [PATCH v2] i2c/designware: enable i2c controller to suspend/resume asynchronously From: Andy Shevchenko To: Jarkko Nikula , "Fu, Zhonghui" , Mika Westerberg , Wolfram Sang Cc: linux-i2c@vger.kernel.org, "linux-kernel@vger.kernel.org" Date: Mon, 01 Feb 2016 17:16:03 +0200 In-Reply-To: <56AF73E1.7080501@linux.intel.com> References: <569893D1.5050403@linux.intel.com> <56AF73E1.7080501@linux.intel.com> Organization: Intel Finland Oy Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.18.3-1 Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2016-02-01 at 17:04 +0200, Jarkko Nikula wrote: > On 01/15/2016 08:38 AM, Fu, Zhonghui wrote: > > Now, PM core supports asynchronous suspend/resume mode for devices > > during system suspend/resume, and the power state transition of one > > device may be completed in separate kernel thread. PM core ensures > > all power state transition dependency between devices. This patch > > enables designware i2c controllers to suspend/resume > > asynchronously. > > This will take advantage of multicore and improve system > > suspend/resume > > speed. After enabling all i2c devices, i2c adapters and i2c > > controllers > > on ASUS T100TA tablet, the system suspend-to-idle time is reduced > > to > > about 510ms from 750ms, and the system resume time is reduced to > > about > > 790ms from 900ms. > > > > Signed-off-by: Zhonghui Fu > > --- > > Changes in v2: > > - Move the device_enable_async_suspend() call into i2c_dw_proble() > > > >   drivers/i2c/busses/i2c-designware-core.c |    1 + > >   1 files changed, 1 insertions(+), 0 deletions(-) > > > > diff --git a/drivers/i2c/busses/i2c-designware-core.c > > b/drivers/i2c/busses/i2c-designware-core.c > > index ba9732c..5d6ad27 100644 > > --- a/drivers/i2c/busses/i2c-designware-core.c > > +++ b/drivers/i2c/busses/i2c-designware-core.c > > @@ -861,6 +861,7 @@ int i2c_dw_probe(struct dw_i2c_dev *dev) > > > >    init_completion(&dev->cmd_complete); > >    mutex_init(&dev->lock); > > + device_enable_async_suspend(dev->dev); > > > I'm aware Andy had concerns about about stability and you also > mention  > in another thread: > > "if enable all LPSS devices suspend/resume asynchronously, the > system  > can't resume sometimes on ASUS T100TA(BayTrail-T SoC). But, I have  > verified that the system can resume normally every time if enable > only  > i2c controller async mode and let other LPSS devices in sync mode on  > ASUS T100TA.". > > What I'm thinking would this change move things forward and help to > find  > out what potential underlying issues there are in LPSS code. > > I'm fine with this I2C side change but can we assure we don't  > accidentally enable the same on other LPSS devices before finding > the  > root cause for the crash? Besides that we have to be really aware about DMA power related fix introduced in v4.5-rc1 in acpi_lpss.c [1]. So, I would like to see a wide testing especially on Intel Baytrail / Braswell platforms before enabling it. [1] http://comments.gmane.org/gmane.linux.acpi.devel/80263 -- Andy Shevchenko Intel Finland Oy