Re: [Update][PATCH 6/10] PM / Domains: System-wide transitions support for generic domains (v5)

Rafael J. Wysocki
2011-07-09T14:15:38Z

On Friday, July 08, 2011, Rafael J. Wysocki wrote:
...
>
> Well, in fact, since we already have .active_wakeup(), what about the
> following patch (on top of https://lkml.org/lkml/2011/7/8/223):

Well, it is wrong, because we've been discussing devices that are _not_
enabled to wake up the system.

> ---
> drivers/base/power/domain.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> Index: linux-2.6/drivers/base/power/domain.c
> =================================> --- linux-2.6.orig/drivers/base/power/domain.c
> +++ linux-2.6/drivers/base/power/domain.c
> @@ -519,6 +519,10 @@ static int pm_genpd_prepare(struct devic
> return -EBUSY;
> }
>
> + if (device_may_wakeup(dev)

So, this should have been !device_may_wakeup(dev), _but_ ...

> + && !(genpd->active_wakeup && genpd->active_wakeup(dev)))
> + pm_runtime_resume(dev);
> +
> genpd_acquire_lock(genpd);
>
> if (genpd->prepared_count++ = 0)

There's one more case to consider, namely devices that are runtime
suspended, set up to wake up the system from sleep states (ie. device_may_wakeup(dev)
returns "true") and such that genpd->active_wakeup(dev) returns "true" for them,
because they need to be resumed at this point too (arguably, it makes a little
sense to runtime suspend such devices, but that's possible in principle).

So, IMO, the patch should look like this:

---
drivers/base/power/domain.c | 19 +++++++++++++++++++
1 file changed, 19 insertions(+)

Index: linux-2.6/drivers/base/power/domain.c
=================================--- linux-2.6.orig/drivers/base/power/domain.c
+++ linux-2.6/drivers/base/power/domain.c
@@ -486,6 +486,22 @@ static void pm_genpd_sync_poweroff(struc
}

/**
+ * resume_needed - Check whether to resume a device before system suspend.
+ * @dev: Device to handle.
+ * @genpd: PM domain the device belongs to.
+ */
+static bool resume_needed(struct device *dev, struct generic_pm_domain *genpd)
+{
+ bool active_wakeup;
+
+ if (!device_can_wakeup(dev))
+ return false;
+
+ active_wakeup = genpd->active_wakeup && genpd->active_wakeup(dev);
+ return device_may_wakeup(dev) ? active_wakeup : !active_wakeup;
+}
+
+/**
* pm_genpd_prepare - Start power transition of a device in a PM domain.
* @dev: Device to start the transition of.
*
@@ -519,6 +535,9 @@ static int pm_genpd_prepare(struct devic
return -EBUSY;
}

+ if (resume_needed(dev, genpd))
+ pm_runtime_resume(dev);
+
genpd_acquire_lock(genpd);

if (genpd->prepared_count++ = 0)