On Sat, Oct 22 2016 at 18:19 -0600, Rafael J. Wysocki wrote:
On Friday, October 21, 2016 03:52:55 PM Lina Iyer wrote:
Update documentation to reflect the changes made to support IRQ safe PM
domains.
Signed-off-by: Lina Iyer <lina.iyer@xxxxxxxxxx>
Acked-by: Ulf Hansson <ulf.hansson@xxxxxxxxxx>
---
Changes since v3:
- Moved para to the end of the section
- Added clause for all IRQ safe devices in a domain
- Cleanup explanation of nested domains
---
Documentation/power/devices.txt | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)
diff --git a/Documentation/power/devices.txt b/Documentation/power/devices.txt
index 8ba6625..9218ce6 100644
--- a/Documentation/power/devices.txt
+++ b/Documentation/power/devices.txt
@@ -607,7 +607,9 @@ individually. Instead, a set of devices sharing a power resource can be put
into a low-power state together at the same time by turning off the shared
power resource. Of course, they also need to be put into the full-power state
together, by turning the shared power resource on. A set of devices with this
-property is often referred to as a power domain.
+property is often referred to as a power domain. A power domain may also be
+nested inside another power domain. The nested domain is referred to as the
+sub-domain of the parent domain.
Support for power domains is provided through the pm_domain field of struct
device. This field is a pointer to an object of type struct dev_pm_domain,
@@ -629,6 +631,13 @@ support for power domains into subsystem-level callbacks, for example by
modifying the platform bus type. Other platforms need not implement it or take
it into account in any way.
+Devices and PM domains may be defined as IRQ-safe, if they can be powered
+on/off even when the IRQs are disabled.
What IRQ-safe means for devices is that their runtime PM callbacks may be
invoked with interrupts disabled on the local CPU. I guess the meaning of
IRQ-safe for PM domains is analogous, but the above isn't precise enough to me.
An IRQ-safe device in a domain will
+disallow power management on the domain, unless the domain is also defined as
+IRQ-safe. In other words, a domain containing all IRQ-safe devices must also
+be defined as IRQ-safe. Another restriction this framework imposes on the
+parent domain of an IRQ-safe domain is that the parent domain must also be
+defined as IRQ-safe.
What about this:
"Devices may be defined as IRQ-safe which indicates to the PM core that their
runtime PM callbacks may be invoked with disabled interrupts (see
Documentation/power/runtime_pm.txt for more information). If an IRQ-safe
device belongs to a PM domain, the runtime PM of the domain will be disallowed,
unless the domain itself is defined as IRQ-safe. However, a PM domain can only
be defined as IRQ-safe if all of the devices in it are IRQ-safe.
This is correct. But the last line may need a bit of modification. If
all devices in a PM domain are IRQ-safe and the domain is NOT, then it
it is a valid combination just that the domain would never do runtime
PM.
Moreover, if
an IRQ-safe domain has a parent domain, the runtime PM of the parent is only
allowed if the parent itself is IRQ-safe too with the additional restriction
that all child domains of an IRQ-safe parent must also be IRQ-safe."
Does it actually reflect what the code does?
Yes, this precisely reflects the code.
Thanks,
Lina
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