On Sun, 2012-11-11 at 21:36 -0500, Alan Stern wrote: > On Mon, 12 Nov 2012, Huang Ying wrote: > > > > The first question: How should the PCI subsystem prevent the parents of > > > driverless VGA devices from being runtime suspended while userspace is > > > accessing them? > > > > I think Rafael's patch is good for that. > > But his patch isn't needed if we make these other changes.
Yes. > > > The second question: Should the PM core allow devices that are disabled > > > for runtime PM to be in the SUSPENDED state when > > > dev->power.runtime_auto is clear? > > > > I think that should not be allowed. > > Disallowing it is okay with me too. But it will require several > changes to the code, more than what your patch did. Yes. I think so too. > > > Assuming we don't want to allow this, there's a third question: Should > > > pm_runtime_allow call pm_runtime_set_suspended if the device is > > > disabled? > > > > Is it absolute necessary to call pm_runtime_set_suspended? If the > > device is disabled, the transition to SUSPENDED state will not be > > triggered even if the device is ACTIVE. > > It's not absolutely necessary to do this, but we ought to because it > will allow the device's parent to be suspended. If we leave the device > in the ACTIVE state then the parent can't be suspended, even when the > device is disabled. I think this is the hard part of the issue. Now "disabled" and SUSPENDED state is managed by hand. IMHO, if we changed pm_runtime_allow() as you said, we need to change the rule too. Maybe something as follow: - remove pm_runtime_set_suspended/pm_runtime_set_active - in pm_runtime_disable/pm_runtime_allow, put device into SUSPENDED state if runtime PM is not forbidden. - in pm_runtime_forbid/pm_runtime_enable, put device into ACTIVE state. Best Regards, Huang Ying -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
