On Tuesday, June 09, 2015 01:42:00 AM Rafael J. Wysocki wrote:
> On Monday, June 01, 2015 05:47:57 PM Andy Shevchenko wrote:
> > From: Heikki Krogerus <heikki.krogerus@xxxxxxxxxxxxxxx>
> >
> > If the parent is still suspended when driver probe is
> > attempted, the result may be failure.
> >
> > For example, if the parent is a PCI MFD device that has been
> > suspended when we try to probe our device, any register
> > reads will return 0xffffffff.
> >
> > To fix the problem, making sure the parent is always awake
> > before attempting driver probe.
> >
> > Signed-off-by: Heikki Krogerus <heikki.krogerus@xxxxxxxxxxxxxxx>
> > Signed-off-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
> > ---
> > drivers/base/dd.c | 8 ++++++++
> > 1 file changed, 8 insertions(+)
> >
> > diff --git a/drivers/base/dd.c b/drivers/base/dd.c
> > index e843fdb..cfbeff3 100644
> > --- a/drivers/base/dd.c
> > +++ b/drivers/base/dd.c
> > @@ -399,6 +399,8 @@ EXPORT_SYMBOL_GPL(wait_for_device_probe);
> > *
> > * This function must be called with @dev lock held. When called for a
> > * USB interface, @dev->parent lock must be held as well.
> > + *
> > + * If device has a parent it will be powered on during device's probe().
> > */
> > int driver_probe_device(struct device_driver *drv, struct device *dev)
> > {
> > @@ -410,10 +412,16 @@ int driver_probe_device(struct device_driver *drv, struct device *dev)
> > pr_debug("bus: '%s': %s: matched device %s with driver %s\n",
> > drv->bus->name, __func__, dev_name(dev), drv->name);
> >
> > + if (dev->parent)
> > + pm_runtime_get_sync(dev->parent);
> > +
>
> For some bus types that will resume and suspend the parent for many times in
> a row in device_attach() until an appropriate driver is found. Would it be
> more efficient to call it once before the bus_for_each_drv() loop in there?
Actually, something like the below should work too (the bumping up of the
parent's usage counter before the loop will keep it in the runtime-active
state throughout the loop).
---
drivers/base/dd.c | 14 ++++++++++++++
1 file changed, 14 insertions(+)
Index: linux-pm/drivers/base/dd.c
===================================================================
--- linux-pm.orig/drivers/base/dd.c
+++ linux-pm/drivers/base/dd.c
@@ -399,6 +399,8 @@ EXPORT_SYMBOL_GPL(wait_for_device_probe)
*
* This function must be called with @dev lock held. When called for a
* USB interface, @dev->parent lock must be held as well.
+ *
+ * If the device has a parent, runtime-resume the parent before driver probing.
*/
int driver_probe_device(struct device_driver *drv, struct device *dev)
{
@@ -410,10 +412,16 @@ int driver_probe_device(struct device_dr
pr_debug("bus: '%s': %s: matched device %s with driver %s\n",
drv->bus->name, __func__, dev_name(dev), drv->name);
+ if (dev->parent)
+ pm_runtime_get_sync(dev->parent);
+
pm_runtime_barrier(dev);
ret = really_probe(dev, drv);
pm_request_idle(dev);
+ if (dev->parent)
+ pm_runtime_put(dev->parent);
+
return ret;
}
@@ -459,8 +467,14 @@ int device_attach(struct device *dev)
ret = 0;
}
} else {
+ if (dev->parent)
+ pm_runtime_get_sync(dev->parent);
+
ret = bus_for_each_drv(dev->bus, NULL, dev, __device_attach);
pm_request_idle(dev);
+
+ if (dev->parent)
+ pm_runtime_put(dev->parent);
}
out_unlock:
device_unlock(dev);
--
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