On Mon, Jul 09, 2018 at 05:52:49PM +0200, Takashi Iwai wrote: > On Mon, 09 Jul 2018 17:47:34 +0200, Lukas Wunner wrote: > > Since v4.17, every time the GPU is powered up, the HDA controller is > > runtime resumed to PCI_D0. (See the call to pci_wakeup_bus() in > > vga_switcheroo_runtime_resume() added by dcac86b7d0.) > > > > If the HDA controller can't detect presence of an HDMI display even > > if it's in PCI_D0, then I suppose that needs to be adressed in the HDA > > driver. Thus so far I don't see the need to call from amdgpu into the > > HDA driver. > > It's not about the PCI power state, but the problem is that the > detection of the HDMI and its ELD read is somewhat asynchronous. > Basically it's handled via the hardware unsolicited event emitted over > HD-audio bus, which was originally generated by GPU at dealing with > the hotplug/unplug. So, this part is racy and not 100% reliable -- > although usually it shouldn't be a big problem. > > That said, it's not the exact "need" but it would make things more > reliable and accurate (even consumes less power as we don't need to > power up/down just for the HDMI detection). Okay. If amdgpu triggers the event on the HDA bus, it should call pm_runtime_get_sync() on the HDA device beforehand. Which device needs to be resumed exactly to ensure ELD reception, the PCI one or the codec? Thanks, Lukas
