From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754181Ab2ITVv5 (ORCPT ); Thu, 20 Sep 2012 17:51:57 -0400 Received: from ogre.sisk.pl ([193.178.161.156]:37041 "EHLO ogre.sisk.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751541Ab2ITVvz (ORCPT ); Thu, 20 Sep 2012 17:51:55 -0400 From: "Rafael J. Wysocki" To: Kevin Hilman , Alan Stern Subject: Re: [PATCH RESEND] PM / Runtime: let rpm_resume() succeed if RPM_ACTIVE, even when disabled Date: Thu, 20 Sep 2012 23:58:24 +0200 User-Agent: KMail/1.13.6 (Linux/3.6.0-rc6+; KDE/4.6.0; x86_64; ; ) Cc: linux-pm@vger.kernel.org, linux-omap@vger.kernel.org, Santosh Shilimkar , Grygorii Strashko , Nishanth Menon , LKML References: <1348176542-28983-1-git-send-email-khilman@deeprootsystems.com> In-Reply-To: <1348176542-28983-1-git-send-email-khilman@deeprootsystems.com> MIME-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-2" Content-Transfer-Encoding: 7bit Message-Id: <201209202358.24400.rjw@sisk.pl> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thursday, September 20, 2012, Kevin Hilman wrote: > From: Kevin Hilman > > When runtime PM is disabled, what we want is for callbacks not to be > called from then on. However, currently, when runtime PM is disabled, > operations such as 'get' will also fail even if the device is > currently active. > > Since calling 'get' on a device that is already RPM_ACTIVE does not > involve calling the callbacks, it should be allowed to succeed, even > if runtime PM is disabled. > > This is particularily useful in runtime PM enabled drivers that are > used during system suspend. Because runtime PM is disabled during > system suspend, currently any driver's use of pm_runtime_get* will > fail with -EACCES. This is expected if the device was already runtime > suspended, but if the device is actually active (due to recent usage, > autosuspend timeout not expired, or pm_runtime_resume() called in > ->suspend() method), the pm_runtime_get*() call should actually > succeed. I'd say the problem is when the drive in question uses the return value of pm_runtime_get_sync(), for example, to decide whether or not it is safe to access the hardware. In that case it may decide that accessing the hardware is unsafe during system suspend, although that's not really the case. So the change you're proposing allows drivers of this kind (and there may be a substantial number of them) to be simplified slightly. > To permit the usage described above, add a check to rpm_resume() so > that success is returned in the case where a driver is suspended (it's > ->suspend callback has been called) but is still RPM_ACTIVE. > > This patch was developed in close collaboration with Rafael J. Wysocki > > > Tested on AM3730/Beagle-xM where wakeup IRQ firing during the late > suspend phase triggers runtime PM activity in the I2C driver since the > wakeup IRQ is on an I2C-connected PMIC. > > Cc: Rafael J. Wysocki > Signed-off-by: Kevin Hilman OK, I wonder if anyone has any objections against this. Alan? Rafael > --- > This version is just a resend with the vger address for linux-pm. > > drivers/base/power/runtime.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c > index 7d9c1cb..dafa5ec 100644 > --- a/drivers/base/power/runtime.c > +++ b/drivers/base/power/runtime.c > @@ -510,7 +510,8 @@ static int rpm_resume(struct device *dev, int rpmflags) > if (dev->power.runtime_error) > retval = -EINVAL; > else if (dev->power.disable_depth > 0) > - retval = -EACCES; > + retval = dev->power.is_suspended && > + dev->power.runtime_status == RPM_ACTIVE ? 1 : -EACCES; > if (retval) > goto out; > >