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Date: Thu, 08 Nov 2012 00:09:19 +0100
From: "Rafael J. Wysocki" <rjw@...k.pl>
To: Alan Stern <stern@...land.harvard.edu>
Cc: Huang Ying <ying.huang@...el.com>, linux-kernel@...r.kernel.org,
linux-pm@...r.kernel.org
Subject: Re: [BUGFIX] PM: Fix active child counting when disabled and forbidden
On Wednesday, November 07, 2012 11:51:15 PM Rafael J. Wysocki wrote:
> On Wednesday, November 07, 2012 04:56:49 PM Alan Stern wrote:
> > On Wed, 7 Nov 2012, Rafael J. Wysocki wrote:
> >
> > > > Right. The reasoning behind my proposal goes like this: When there's
> > > > no driver, the subsystem can let userspace directly control the
> > > > device's power level through the power/control attribute.
> > >
> > > Well, we might as well just leave the runtime PM of PCI devices enabled, even
> > > if they have no drivers, but modify the PCI bus type's runtime PM callbacks
> > > to ignore devices with no drivers.
> > >
> > > IIRC the reason why we decided to disable runtime PM for PCI device with no
> > > drivers was that some of them refused to work again after being put by the
> > > core into D3. By making the PCI bus type's runtime PM callbacks ignore them
> > > we'd avoid this problem without modifying the core's behavior.
> >
> > It comes down to a question of the parent. If a driverless PCI device
> > isn't being used, shouldn't its parent be allowed to go into runtime
> > suspend? As things stand now, we do allow it.
> >
> > The problem is that we don't disallow it when the driverless device
> > _is_ being used.
>
> We can make it depend on what's there in the control file. Let's say if that's
> "on" (ie. the devices usage counter is not zero), we won't allow the parent
> to be suspended.
>
> So, as I said, why don't we keep the runtime PM of PCI devices always enabled,
> regardless of whether or not there is a driver, and arrange things in such a
> way that the device is automatically "suspended" if user space writes "auto"
> to the control file. IOW, I suppose we can do something like this:
It probably is better to treat the "no driver" case in a special way, though:
---
drivers/pci/pci-driver.c | 45 +++++++++++++++++++++++++--------------------
drivers/pci/pci.c | 2 ++
2 files changed, 27 insertions(+), 20 deletions(-)
Index: linux-pm/drivers/pci/pci-driver.c
===================================================================
--- linux-pm.orig/drivers/pci/pci-driver.c
+++ linux-pm/drivers/pci/pci-driver.c
@@ -263,22 +263,17 @@ static long local_pci_probe(void *_ddi)
/* The parent bridge must be in active state when probing */
if (parent)
pm_runtime_get_sync(parent);
- /* Unbound PCI devices are always set to disabled and suspended.
- * During probe, the device is set to enabled and active and the
- * usage count is incremented. If the driver supports runtime PM,
- * it should call pm_runtime_put_noidle() in its probe routine and
+ /*
+ * During probe, the device is set to active and the usage count is
+ * incremented. If the driver supports runtime PM, it should call
+ * pm_runtime_put_noidle() in its probe routine and
* pm_runtime_get_noresume() in its remove routine.
*/
- pm_runtime_get_noresume(dev);
- pm_runtime_set_active(dev);
- pm_runtime_enable(dev);
-
+ pm_runtime_get_sync(dev);
rc = ddi->drv->probe(ddi->dev, ddi->id);
- if (rc) {
- pm_runtime_disable(dev);
- pm_runtime_set_suspended(dev);
- pm_runtime_put_noidle(dev);
- }
+ if (rc)
+ pm_runtime_put_sync(dev);
+
if (parent)
pm_runtime_put(parent);
return rc;
@@ -369,9 +364,7 @@ static int pci_device_remove(struct devi
}
/* Undo the runtime PM settings in local_pci_probe() */
- pm_runtime_disable(dev);
- pm_runtime_set_suspended(dev);
- pm_runtime_put_noidle(dev);
+ pm_runtime_put_sync(dev);
/*
* If the device is still on, set the power state as "unknown",
@@ -998,10 +991,14 @@ static int pci_pm_restore(struct device
static int pci_pm_runtime_suspend(struct device *dev)
{
struct pci_dev *pci_dev = to_pci_dev(dev);
- const struct dev_pm_ops *pm = dev->driver ? dev->driver->pm : NULL;
+ const struct dev_pm_ops *pm;
pci_power_t prev = pci_dev->current_state;
int error;
+ if (!dev->driver)
+ return 0;
+
+ pm = dev->driver->pm;
if (!pm || !pm->runtime_suspend)
return -ENOSYS;
@@ -1035,8 +1032,12 @@ static int pci_pm_runtime_resume(struct
{
int rc;
struct pci_dev *pci_dev = to_pci_dev(dev);
- const struct dev_pm_ops *pm = dev->driver ? dev->driver->pm : NULL;
+ const struct dev_pm_ops *pm;
+
+ if (!dev->driver)
+ return 0;
+ pm = dev->driver->pm;
if (!pm || !pm->runtime_resume)
return -ENOSYS;
@@ -1054,8 +1055,12 @@ static int pci_pm_runtime_resume(struct
static int pci_pm_runtime_idle(struct device *dev)
{
- const struct dev_pm_ops *pm = dev->driver ? dev->driver->pm : NULL;
+ const struct dev_pm_ops *pm;
+
+ if (!dev->driver)
+ goto out:
+ pm = dev->driver->pm;
if (!pm)
return -ENOSYS;
@@ -1065,8 +1070,8 @@ static int pci_pm_runtime_idle(struct de
return ret;
}
+ out:
pm_runtime_suspend(dev);
-
return 0;
}
Index: linux-pm/drivers/pci/pci.c
===================================================================
--- linux-pm.orig/drivers/pci/pci.c
+++ linux-pm/drivers/pci/pci.c
@@ -1868,6 +1868,8 @@ void pci_pm_init(struct pci_dev *dev)
u16 pmc;
pm_runtime_forbid(&dev->dev);
+ pm_runtime_set_active(dev);
+ pm_runtime_enable(&dev->dev);
device_enable_async_suspend(&dev->dev);
dev->wakeup_prepared = false;
--
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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