On Tue, Apr 13, 2021 at 10:24 AM Roy Spliet <nouveau@xxxxxxxxxx> wrote: > > Op 13-04-2021 om 01:10 schreef Karol Herbst: > > On Mon, Apr 12, 2021 at 9:36 PM Roy Spliet <nouveau@xxxxxxxxxx> wrote: > >> > >> Hello Aaron, > >> > >> Thanks for your insights. A follow-up query and some observations in-line. > >> > >> Op 12-04-2021 om 20:06 schreef Aaron Plattner: > >>> On 4/10/21 1:48 PM, Roy Spliet wrote: > >>>> Op 10-04-2021 om 20:23 schreef Lukas Wunner: > >>>>> On Sat, Apr 10, 2021 at 04:51:27PM +0100, Roy Spliet wrote: > >>>>>> Can I ask someone with more > >>>>>> technical knowledge of snd_hda_intel and vgaswitcheroo to brainstorm > >>>>>> about > >>>>>> the possible challenges of nouveau taking matters into its own hand > >>>>>> rather > >>>>>> than keeping this PCI quirk around? > >>>>> > >>>>> It sounds to me like the HDA is not powered if no cable is plugged in. > >>>>> What is reponsible then for powering it up or down, firmware code on > >>>>> the GPU or in the host's BIOS? > >>>> > >>>> Sometimes the BIOS, but definitely unconditionally the PCI quirk code: > >>>> https://github.com/torvalds/linux/blob/master/drivers/pci/quirks.c#L5289 > >>>> > >>>> (CC Aaron Plattner) > >>> > >>> My basic understanding is that the audio function stops responding > >>> whenever the graphics function is powered off. So the requirement here > >>> is that the audio driver can't try to talk to the audio function while > >>> the graphics function is asleep, and must trigger a graphics function > >>> wakeup before trying to communicate with the audio function. > >> > >> I believe that vgaswitcheroo takes care of this for us. > >> > > > > yeah, and also: why would the driver want to do stuff? If the GPU is > > turned off, there is no point in communicating with the audio device > > anyway. The driver should do the initial probe and leave the device be > > unless it's actively used. Also there is no such thing as "use the > > audio function, but not the graphics one" > > > >>> I think > >>> there are also requirements about the audio function needing to be awake > >>> when the graphics driver is updating the ELD, but I'm not sure. > >>> > > > > well, it's one physical device anyway, so technically the audio > > function is powered on. > > > >>> This is harder on Windows because the audio driver lives in its own > >>> little world doing its own thing but on Linux we can do better. > >>> > >>>>> Ideally, we should try to find out how to control HDA power from the > >>>>> operating system rather than trying to cooperate with whatever firmware > >>>>> is doing. If we have that capability, the OS should power the HDA up > >>>>> and down as it sees fit. > >>> > >>> After system boot, I don't think there's any firmware involved, but I'm > >>> not super familiar with the low-level details and it's possible the > >>> situation changed since I last looked at it. > >>> > >>> I think the problem with having nouveau write this quirk is that the > >>> kernel will need to re-probe the PCI device to notice that it has > >>> suddenly become a multi-function device with an audio function, and > >>> hotplug the audio driver. I originally looked into trying to do that but > >>> it was tricky because the PCI subsystem didn't really have a mechanism > >>> for a single-function device to become a multi-function device on the > >>> fly and it seemed easier to enable it early on during bus enumeration. > >>> That way the kernel sees both functions all the time without anything > >>> else having to be special about this configuration. > > > > Well, we do have this pci/quirk.c thing, no? Nouveau does flip the > > bit, but I am actually not sure if that's even doing something > > anymore. Maybe in the runtime_resume case it's still relevant but not > > sure _when_ DECLARE_PCI_FIXUP_CLASS_RESUME_EARLY is triggered, it does > > seem to be called even in the runtime_resume case though. > > > >> > >> Right, so for a little more context: a while ago I noticed that my > >> laptop (lucky me, Asus K501UB) has a 940M with HDA but no codec. Seems > >> legit, given how this GPU has no displays attached; they're all hooked > >> up to the Intel integrated GPU. That threw off the snd_hda_intel > >> mid-probe, and as a result didn't permit runpm, keeping the entire GPU, > >> PCIe bus and thus the CPU package awake. A bit of hackerly later we > >> decided to continue probing without a codec, and now my laptop is happy, > >> but... > >> A new problem popped up with several other NVIDIA GPUs that expose their > >> HDA subdevice, but somehow its inaccessible. Relevant lines from a > >> users' log: > >> > >> [ 3.031222] MXM: GUID detected in BIOS > >> [ 3.031280] ACPI BIOS Error (bug): AE_AML_PACKAGE_LIMIT, Index > >> (0x000000003) is beyond end of object (length 0x0) (20200925/exoparg2-393) > >> [ 3.031352] ACPI Error: Aborting method \_SB.PCI0.GFX0._DSM due to > >> previous error (AE_AML_PACKAGE_LIMIT) (20200925/psparse-529) > >> [ 3.031419] ACPI: \_SB_.PCI0.GFX0: failed to evaluate _DSM (0x300b) > >> [ 3.031424] ACPI Warning: \_SB.PCI0.GFX0._DSM: Argument #4 type > >> mismatch - Found [Buffer], ACPI requires [Package] (20200925/nsarguments-61) > >> [ 3.031619] pci 0000:00:02.0: optimus capabilities: enabled, status > >> dynamic power, > >> [ 3.031667] ACPI BIOS Error (bug): AE_AML_PACKAGE_LIMIT, Index > >> (0x000000003) is beyond end of object (length 0x0) (20200925/exoparg2-393) > >> [ 3.031731] ACPI Error: Aborting method \_SB.PCI0.GFX0._DSM due to > >> previous error (AE_AML_PACKAGE_LIMIT) (20200925/psparse-529) > >> [ 3.031791] ACPI Error: Aborting method \_SB.PCI0.PEG0.PEGP._DSM due > >> to previous error (AE_AML_PACKAGE_LIMIT) (20200925/psparse-529) > >> [ 3.031856] ACPI: \_SB_.PCI0.PEG0.PEGP: failed to evaluate _DSM (0x300b) > >> [ 3.031859] ACPI Warning: \_SB.PCI0.PEG0.PEGP._DSM: Argument #4 type > >> mismatch - Found [Buffer], ACPI requires [Package] (20200925/nsarguments-61) > > > > If I am not wrong we are calling the _DSM method inside nouveau when > > doing runpm on pre _PR3 systems. As this is all very vendor specific, > > we might be doing something incorrectly. > > > >> [ 3.032058] pci 0000:01:00.0: optimus capabilities: enabled, status > >> dynamic power, > >> [ 3.032061] VGA switcheroo: detected Optimus DSM method > >> \_SB_.PCI0.PEG0.PEGP handle > >> [ 3.032323] checking generic (d0000000 410000) vs hw (f6000000 1000000) > >> [ 3.032325] checking generic (d0000000 410000) vs hw (e0000000 10000000) > >> [ 3.032326] checking generic (d0000000 410000) vs hw (f0000000 2000000) > >> [ 3.032410] nouveau 0000:01:00.0: NVIDIA GK107 (0e71f0a2) > >> [ 3.042385] nouveau 0000:01:00.0: bios: version 80.07.a0.00.11 > >> --- snip --- > >> [ 8.951478] snd_hda_intel 0000:01:00.1: can't change power state from > >> D3cold to D0 (config space inaccessible) > >> [ 8.951509] snd_hda_intel 0000:01:00.1: can't change power state from > >> D3hot to D0 (config space inaccessible) > > > > This is actually a little bad, because it means that the device > > doesn't come back up from D3. It's a bit weird it's D3cold and D3hot > > in the messages, but maybe the device just takes quite some time to > > wake up. But it does look like the device gets woken up. > > > >> [ 8.951608] snd_hda_intel 0000:01:00.1: Disabling MSI > >> [ 8.951621] snd_hda_intel 0000:01:00.1: Handle vga_switcheroo audio > >> client > >> [ 8.952461] snd_hda_intel 0000:00:1b.0: bound 0000:00:02.0 (ops > >> i915_audio_component_bind_ops [i915]) > >> [ 8.952642] snd_hda_intel 0000:01:00.1: number of I/O streams is 30, > >> forcing separate stream tags > >> > >> Now I don't know what's going on, but the snd_hda_intel messages are > >> ominous. And so are the ACPI warnings. But I don't know how much these > >> two are related. > >> > > > > What is the actual problem though? Seems like everything is fine > > despite those messages. > > The problem, as stated a few e-mails earlier, is that the HDA errors > currently prevent snd_hda_intel from properly probing the device and > registering it with vgaswitcheroo. As a result, the GPU always stays in > DynPwr rather than DynOff even when it's unused, keeping the PCIe bus > and the CPU package powered. Basically burning through a charged battery > a lot quicker than need be. That's not the result of those errors, just the result of having no codecs, no? > If we go back a mile on the e-mail thread, I think the problem was > narrowed down to snd_hda_intel reading an invalid codec mask on the > config space, and using it anyway. That being said, I believe there are > also reports of users that don't get HDMI audio unless the cable was > plugged in at boot-time, with similar messages in their logs. The codec > might in such cases be hiding themselves until a cable is plugged in? > @Aaron Plattner: does that latter observation sound right to you? > yeah, I think that's the thing we should focus on, everything else just seems unrelated at this point until we have more information (like, codecs hide, because the _DSM calls failed or something) > > > >> You say that it is desirable to switch on HDA at boot-time because the > >> PCI subsystem doesn't play nicely with changing a device to > >> multi-function. That rules out the option of only enabling the HDA > >> device once a cable is plugged in. Are there any other trap doors that > > > > yeah, we can absolutely not do that. We do quirk the device to put the > > GPU into multi function state asap and the intel_hda_snd driver should > > deal with it. > > > >> snd_hda_intel needs to navigate around to make this work fault free on > >> all hardware, such as: > >> - Codecs not revealing themselves until a display is plugged in, > >> requiring perhaps a "codec reprobe" and "codec remove" event from > >> nouveau/rm to snd_hda_intel, > > > > we could trigger the reprobe from within nouveau as we are dealing > > with display hotplug events anyway. > > Right. Are there situations where nouveau needs to? Or is this a > misunderstanding of the problem from my end? > nouveau has to do some configuration anyway, like connecting the audio stream with the port used etc...that's the ELD part. We have some drm_audio bits though, so maybe we can solve this more general and maybe the radeon drivers already have something here? Might be worth to take a look there as well. > > > >> - Borked BIOSes just blindly assigning the MMIO space of the HDA device > >> to another device, or nothing at all, > > > > that exists? *sigh* > > > >> - ... other things that might give any of us nightmares and heart burn? > >> > > > > hopefully there are none :p > > > >> Thanks! > >> > >> Roy > >> > >>> > >>> -- Aaron > >>> > >>>>> Thanks, > >>>>> > >>>>> Lukas > >> > > >
