On Tuesday, September 11, 2012, Alan Stern wrote: > On Tue, 11 Sep 2012, Rafael J. Wysocki wrote: > > > Hi, > > > > On Tuesday, September 11, 2012, Dave Airlie wrote: > > > Hi Rafael, > > > > > > I've been investigating runtime PM support for some use-cases on GPUs. > > > > > > In some laptops we have a secondary GPU (optimus) that can be powered > > > up for certain 3D tasks and then turned off when finished with. Now I > > > did an initial pass on supporting it without using the kernel runtime > > > PM stuff, but Alan said I should take a look so here I am. > > > > Alan Stern or Alan Cox? :-) > > > > > While I've started to get a handle on things, we have a bit of an > > > extra that I'm not sure we cater for. > > > > > > Currently we get called from the PCI layer which after we are finished > > > with our runtime suspend callback, will go put the device into the > > > correct state etc, however on these optimus/powerxpress laptops we > > > have a separate ACPI or platform driver controlled power switch that > > > we need to call once the PCI layer is finished the job. This switch > > > effectively turns the power to the card completely off leaving it > > > drawing no power. > > > > > > No we can't hit the switch from the driver callback as the PCI layer > > > will get lost, so I'm wondering how you'd envisage we could plug this > > > in. > > > > Hmm. In principle we might modify pci_pm_runtime_suspend() so that it > > doesn't call pci_finish_runtime_suspend() if pci_dev->state_saved is > > set. That would actually make it work in analogy with pci_pm_suspend_noirq(), > > so perhaps it's not even too dangerous. > > This sounds more like a job for a power domain. Unless the power > switch is already in the device hierarchy as a parent to the PCI > device. Good idea. :-) Thanks, Rafael _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/dri-devel
