[PATCH v2] driver core / PM: Add PM domain callbacks for device setup/cleanup

[Rafael J. Wysocki]

On Thursday, March 19, 2015 03:42:03 PM Dmitry Torokhov wrote:
> On Thu, Mar 19, 2015 at 2:51 PM, Rafael J. Wysocki <rjw at rjwysocki.net> wrote:
> > From: Rafael J. Wysocki <rafael.j.wysocki at intel.com>
> > Subject: driver core / PM: Add PM domain callbacks for device setup/cleanup
> >
> > If PM domains are in use, it may be necessary to prepare the code
> > handling a PM domain for driver probing.  For example, in some
> > cases device drivers rely on the ability to power on the devices
> > with the help of the IO runtime PM framework and the PM domain
> > code needs to be ready for that.  Also, if that code has not been
> > fully initialized yet, the driver probing should be deferred.
> >
> > Moreover, after the probing is complete, it may be necessary to
> > put the PM domain in question into the state reflecting the current
> > needs of the devices in it, for example, so that power is not drawn
> > in vain.  The same should be done after removing a driver from
> > a device, as the PM domain state may need to be changed to reflect
> > the new situation.
> >
> > For these reasons, introduce new PM domain callbacks, ->activate
> > and ->sync, called, respectively, before probing for a device
> > driver and after the probing has been completed or the driver
> > has been removed.
> >
> > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki at intel.com>
> > ---
> >> ---
> >>
> >> This is an update without the additional bus type callbacks.  This should
> >> be suffucient at this point for the use cases we have.
> >>
> >> I've decided to also call ->sync on driver removal as that is consistent
> >> with what happens for failing probe.
> >>
> >> ---
> >
> > One more update.
> >
> > I've realized that in the PM domain's ->sync callback is called after
> > clearing the device's driver field (in the failed probe or driver removal
> > case) rather than before it, that could be used to distinguish between the
> > two cases (successful probe vs no driver), so I reworked the patch accordingly.
> 
> That is very non-obvious. dev->drv belongs to driver core and maybe
> bus, nothing else should really be looking at it. Why can't we add an
> explicit argument to the callback indicating device state?

Well, if that's a concern, I'd rather introduce a separate callback to
be run on driver removal/failing probe, like in the patch below, as it is
then clear what the conditions for each callback's execution are (and one
can always define them as wrappers around the same routine if need be).

I still think that this ordering of code is the right one, though.

Rafael


---
 drivers/base/dd.c  |   16 ++++++++++++++++
 include/linux/pm.h |    8 ++++++++
 2 files changed, 24 insertions(+)

Index: linux-pm/include/linux/pm.h
===================================================================
--- linux-pm.orig/include/linux/pm.h
+++ linux-pm/include/linux/pm.h
@@ -603,10 +603,18 @@ extern void dev_pm_put_subsys_data(struc
  * Power domains provide callbacks that are executed during system suspend,
  * hibernation, system resume and during runtime PM transitions along with
  * subsystem-level and driver-level callbacks.
+ *
+ * @detach: Called when removing a device from the domain.
+ * @activate: Called before executing probe routines for bus types and drivers.
+ * @sync: Called after successful driver probe.
+ * @dismiss: Called after unsuccessful driver probe and after driver removal.
  */
 struct dev_pm_domain {
 	struct dev_pm_ops	ops;
 	void (*detach)(struct device *dev, bool power_off);
+	int (*activate)(struct device *dev);
+	void (*sync)(struct device *dev);
+	void (*dismiss)(struct device *dev);
 };
 
 /*
Index: linux-pm/drivers/base/dd.c
===================================================================
--- linux-pm.orig/drivers/base/dd.c
+++ linux-pm/drivers/base/dd.c
@@ -279,6 +279,7 @@ static int really_probe(struct device *d
 {
 	int ret = 0;
 	int local_trigger_count = atomic_read(&deferred_trigger_count);
+	struct dev_pm_domain *pm_domain = dev->pm_domain;
 
 	atomic_inc(&probe_count);
 	pr_debug("bus: '%s': %s: probing driver %s with device %s\n",
@@ -298,6 +299,12 @@ static int really_probe(struct device *d
 		goto probe_failed;
 	}
 
+	if (pm_domain && pm_domain->activate) {
+		ret = pm_domain->activate(dev);
+		if (ret)
+			goto probe_failed;
+	}
+
 	if (dev->bus->probe) {
 		ret = dev->bus->probe(dev);
 		if (ret)
@@ -308,6 +315,9 @@ static int really_probe(struct device *d
 			goto probe_failed;
 	}
 
+	if (pm_domain && pm_domain->sync)
+		pm_domain->sync(dev);
+
 	driver_bound(dev);
 	ret = 1;
 	pr_debug("bus: '%s': %s: bound device %s to driver %s\n",
@@ -319,6 +329,8 @@ probe_failed:
 	driver_sysfs_remove(dev);
 	dev->driver = NULL;
 	dev_set_drvdata(dev, NULL);
+	if (pm_domain && pm_domain->dismiss)
+		pm_domain->dismiss(dev);
 
 	if (ret == -EPROBE_DEFER) {
 		/* Driver requested deferred probing */
@@ -522,9 +534,13 @@ static void __device_release_driver(stru
 			dev->bus->remove(dev);
 		else if (drv->remove)
 			drv->remove(dev);
+
 		devres_release_all(dev);
 		dev->driver = NULL;
 		dev_set_drvdata(dev, NULL);
+		if (dev->pm_domain && dev->pm_domain->dismiss)
+			dev->pm_domain->dismiss(dev);
+
 		klist_remove(&dev->p->knode_driver);
 		if (dev->bus)
 			blocking_notifier_call_chain(&dev->bus->p->bus_notifier,