From mboxrd@z Thu Jan 1 00:00:00 1970 From: Lin Ming Subject: Re: [PATCH v3 3/6] [SCSI] runtime resume device before system suspend Date: Fri, 25 Nov 2011 21:50:39 +0800 Message-ID: <1322229039.4246.8.camel@hp6530s> References: Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: Sender: linux-ide-owner@vger.kernel.org To: Alan Stern Cc: Tejun Heo , "linux-kernel@vger.kernel.org" , "linux-ide@vger.kernel.org" , "linux-scsi@vger.kernel.org" , "linux-pm@vger.kernel.org" , Jeff Garzik , "Rafael J. Wysocki" , James Bottomley , "Huang, Ying" , "Zhang, Rui" List-Id: linux-scsi@vger.kernel.org On Fri, 2011-11-25 at 08:17 +0800, Alan Stern wrote: > On Thu, 24 Nov 2011, Tejun Heo wrote: >=20 > > Hello, > >=20 > > On Thu, Nov 24, 2011 at 2:54 PM, Alan Stern wrote: > > > Therefore, when entering the SUSPEND or HIBERNATE stages of syste= m > > > sleep, we can skip the callback to the driver if the device is al= ready > > > in runtime suspend. =EF=BF=BDWhen entering the FREEZE stage, howe= ver, we should > > > first issue a runtime resume. =EF=BF=BDThe overhead of doing this= is > > > negligible, because a suspended drive would be spun up during the= THAW > > > stage of hibernation anyway. > >=20 > > My brain is half fried at the moment so maybe you're saying the sam= e > > thing, but I hope this is something simple. Like... > >=20 > > /* for libata runtime suspend is equivalent to suspend */ > > if (runtime suspended && target =3D=3D SUSPEND) { > > yeah! skip drive pm ops; > > } else { > > end runtime pm; > > ask EH to enter target PM state; > > } >=20 > Almost. More like this: >=20 > /* > * sd is the only high-level SCSI driver to implement runtime=20 > * PM, and sd treats runtime suspend, system suspend, and=20 > * system hibernate identically (but not system freeze). > */ > if (runtime-suspended) { > if (target =3D=3D SUSPEND || target =3D=3D HIBERNATE) > return 0; /* already suspended */ > /* wake up device so that FREEZE will succeed */ > pm_runtime_resume(); > } > tell device driver to enter target PM state Below is the updated patch with your suggested patch description and comments. Looks OK? Subject: [PATCH] [SCSI] check runtime PM status in system PM The only high-level SCSI driver that currently implements runtime PM is sd, and sd treats runtime suspend exactly the same as the SUSPEND and HIBERNATE stages of system sleep, but not the same as the FREEZE stage. Therefore, when entering the SUSPEND or HIBERNATE stages of system sleep, we can skip the callback to the driver if the device is already in runtime suspend. When entering the FREEZE stage, however, we should first issue a runtime resume. The overhead of doing this is negligible, because a suspended drive would be spun up during the THAW stage of hibernation anyway. Signed-off-by: Lin Ming --- drivers/scsi/scsi_pm.c | 16 +++++++++++++++- 1 files changed, 15 insertions(+), 1 deletions(-) diff --git a/drivers/scsi/scsi_pm.c b/drivers/scsi/scsi_pm.c index d329f8b..a633076 100644 --- a/drivers/scsi/scsi_pm.c +++ b/drivers/scsi/scsi_pm.c @@ -49,8 +49,22 @@ static int scsi_bus_suspend_common(struct device *de= v, pm_message_t msg) { int err =3D 0; =20 - if (scsi_is_sdev_device(dev)) + if (scsi_is_sdev_device(dev)) { + /* + * sd is the only high-level SCSI driver to implement runtime + * PM, and sd treats runtime suspend, system suspend, and + * system hibernate identically (but not system freeze). + */ + if (pm_runtime_suspended(dev)) { + if (msg.event =3D=3D PM_EVENT_SUSPEND || + msg.event =3D=3D PM_EVENT_HIBERNATE) + return 0; /* already suspended */ + + /* wake up device so that FREEZE will succeed */ + pm_runtime_resume(dev); + } err =3D scsi_dev_type_suspend(dev, msg); + } return err; } ---=20 Thanks, Lin Ming >=20 > libata does not contain the SCSI device driver; it contains the host > driver. >=20 > > I really don't think we need to optimize this further than this. >=20 > The above has two lines (plus comments) of optimization. Okay? >=20 > Alan Stern >=20