Messages in this thread | | | Date | Mon, 14 Mar 2016 12:23:57 +0200 | From | Mika Westerberg <> | Subject | Re: [PATCH 1/2] vga_switcheroo: add power support for windows 10 machines. |
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On Mon, Mar 14, 2016 at 07:47:39PM +1000, Dave Airlie wrote: > > > >> - if (pcie_port_runtime_suspend_allowed(dev)) > >> + if (pcie_port_runtime_suspend_allowed(dev)) { > >> + pm_runtime_allow(&dev->dev); > > > > PCI drivers typically have left this decision up to the userspace. I'm > > wondering whether it is good idea to deviate from that here? Of course > > this allows immediate power savings but could potentially cause problems > > as well. > > > > No distro has ever shipped userspace to do this, I really think this > is a bad design. > We have wasted countless watts of power on this stupid idea that people will > run powertop, only a few people in the world run powertop, lots of > people use Linux.
That is a fair point.
I do not have anything against calling pm_runtime_allow() here. In fact we already do the same in Intel LPSS drivers. I just wanted to bring that up.
Rafael, what do you think?
If we anyway are going to add cut-off date to enable runtime PM we should expect that the hardware is also capable of doing so (and if not we can always blacklist the exceptions).
> The kernel should power stuff down not wait for the user to run powertop, > At least for the GPU it's in the area of 8W of power, and I've got the > GPU drivers doing this themselves, > > I could have the GPU driver call runtime allow for it's host bridge I suppose, > if we insist on the userspace cares, but I'd prefer not doing so. > > > I think we need to add corresponding call to pm_runtime_forbid() in > > pcie_portdrv_remove(). > > Yes most likely.
BTW, I can add both calls to the next version of PCIe runtime PM patches if you are OK with that, and all agree this is a good idea.
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