On Monday, October 24, 2016 10:16:05 AM Lina Iyer wrote:

On Sat, Oct 22 2016 at 18:19 -0600, Rafael J. Wysocki wrote:

quoted

On Friday, October 21, 2016 03:52:55 PM Lina Iyer wrote:

quoted

Update documentation to reflect the changes made to support IRQ safe PM
domains.

Signed-off-by: Lina Iyer <redacted>
Acked-by: Ulf Hansson <redacted>
---
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.

quoted

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.

That doesn't contradict the last sentence of mine above.  I guess what you mean
is that having a non-IRQ-safe device in an IRQ-safe domain is a valid
configuration.  I wonder how it works then. :-)

In any case, what about changing that sentence to something like:

"However, it only makes sense to define a PM domain as IRQ-safe if all devices
in it are IRQ-safe."

Thanks,
Rafael