On Tue, Mar 24, 2020 at 06:31:08PM +0100, Karol Herbst wrote: > On Sat, Mar 21, 2020 at 2:02 AM Karol Herbst <kherbst@xxxxxxxxxx> wrote: > > > > On Fri, Mar 20, 2020 at 11:19 PM Bjorn Helgaas <helgaas@xxxxxxxxxx> wrote: > > > > > > On Tue, Mar 10, 2020 at 08:26:27PM +0100, Karol Herbst wrote: > > > > Fixes the infamous 'runtime PM' bug many users are facing on Laptops with > > > > Nvidia Pascal GPUs by skipping said PCI power state changes on the GPU. > > > > > > > > Depending on the used kernel there might be messages like those in demsg: > > > > > > > > "nouveau 0000:01:00.0: Refused to change power state, currently in D3" > > > > "nouveau 0000:01:00.0: can't change power state from D3cold to D0 (config > > > > space inaccessible)" > > > > followed by backtraces of kernel crashes or timeouts within nouveau. > > > > > > > > It's still unkown why this issue exists, but this is a reliable workaround > > > > and solves a very annoying issue for user having to choose between a > > > > crashing kernel or higher power consumption of their Laptops. > > > > > > Thanks for the bugzilla link. The bugzilla mentions lots of mailing > > > list discussion. Can you include links to some of that? > > > > > > IIUC this basically just turns off PCI power management for the GPU. > > > Can you do that with something like the following? I don't know > > > anything about DRM, so I don't know where you could save the pm_cap, > > > but I'm sure the driver could keep it somewhere. > > > > > > > Sure this would work? From a quick look over the pci code, it looks > > like a of code would be skipped we really need, like the platform code > > to turn off the GPU via ACPI. But I could also remember incorrectly on > > how all of that worked again. I can of course try and see what the > > effect of this patch would be. And would the parent bus even go into > > D3hot if it knows one of its children is still at D0? Because that's > > what the result of that would be as well, no? And I know that if the > > bus stays in D0, that it has a negative impact on power consumption. > > > > Anyway, I will try that out, I am just not seeing how that would help. > > so it seems like that has worked unless I screwed up locally. Will do > some proper testing and then I think we won't need to go through the > pci tree anymore as no changes are required there with that. Hehe, looks like our responses crossed in the mail :) I hope further testing is still positive; let me know if not. Bjorn
