Messages in this thread | | | Date | Mon, 14 Mar 2016 13:50:41 +0100 | Subject | Re: [PATCH 1/2] vga_switcheroo: add power support for windows 10 machines. | From | "Rafael J. Wysocki" <> |
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On Mon, Mar 14, 2016 at 11:23 AM, Mika Westerberg <mika.westerberg@linux.intel.com> wrote: > 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?
We can do that to start with. If there are no problems in the field with it, I don't see any problems in principle.
> 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).
Sounds reasonable.
>> 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.
That would be fine by me.
Thanks, Rafael
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