On Mon, 09 Jul 2018 17:59:00 +0200, Alex Deucher wrote: > > On Mon, Jul 9, 2018 at 11:52 AM, Takashi Iwai <tiwai@xxxxxxx> wrote: > > On Mon, 09 Jul 2018 17:47:34 +0200, > > Lukas Wunner wrote: > >> > >> On Mon, Jul 09, 2018 at 05:04:22PM +0200, Takashi Iwai wrote: > >> > On Mon, 09 Jul 2018 15:58:51 +0200, Alex Deucher wrote: > >> > > On Mon, Jul 9, 2018 at 6:16 AM, Qu, Jim <Jim.Qu@xxxxxxx> wrote: > >> > > > > You're saying above that the HDA controller isn't runtime resumed on > >> > > > > hotplug of a display. Is that necessary to retrieve ELD or something? > >> > > > > I'm not sure if there's code in the HDA driver to acquire a runtime PM > >> > > > > ref on HPD, but maybe it's necessary. Or maybe the code is there but > >> > > > > somehow no HPD interrupt is received by the HDA driver? > >> > > > > >> > > > So far, I do not find any code about audio response HPD in kernel. > >> > > > the HPD interrupt will sent to user mode via uevent, not sure whether > >> > > > audio user mode driver can receive the event or not. > >> > > > >> > > On the gfx side at least, we can get a hotplug event via ACPI > >> > > (depending on the OEM design) if displays are attached/detached while > >> > > the dGPU is powered down. I suppose the gfx driver could call into > >> > > the audio driver during one of those events. On the gfx side at least > >> > > we just generate the gfx hotplug event and let userspace deal with it. > >> > > >> > IMO, a more proper way would be to have the direct communication > >> > between the graphics driver and the audio driver like i915 driver > >> > does. Then the audio driver can get plug/unplug event at more > >> > accurate timing without races. > >> > >> 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). > > Well for display detection, we don't actually have to wake the GPU, we > get the notification from the embedded controller via ACPI if the GPU > is powered down, so in the GPU driver we just pass the event along to > userspace if the GPU is asleep. I think if we wanted to pass the info > along to the audio driver, we'd need to wake both the GPU and the > audio to update the audio connect status. I guess that It's not enough to have an ACPI event but we need to read ELD upon hotplugging (not at unplugging, of course, though). So a GPU wakeup would be mandatory, if I'm not mistaken. Takashi _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
