On Mon, Dec 21, 2020 at 11:33 AM Kai-Heng Feng kai.heng.feng@canonical.com wrote:
[+Cc nouveau]
On Fri, Dec 18, 2020 at 4:06 PM Takashi Iwai tiwai@suse.de wrote: [snip]
Quite possibly the system doesn't power up HDA controller when there's no external monitor. So when it's connected to external monitor, it's still needed for HDMI audio. Let me ask the user to confirm this.
Yeah, it's the basic question whether the HD-audio is supposed to work on this machine at all. If yes, the current approach we take makes less sense - instead we should rather make the HD-audio controller working.
Yea, confirmed that the Nvidia HDA works when HDMI is connected prior boot.
- The second problem is that pci_enable_device() ignores the error returned from pci_set_power_state() if it's -EIO. And the inaccessible access error returns -EIO, although it's rather a fatal problem. So the driver believes as the PCI device gets enabled properly.
This was introduced in 2005, by Alan's 11f3859b1e85 ("[PATCH] PCI: Fix regression in pci_enable_device_bars") to fix UHCI controller.
- The third problem is that HD-audio driver blindly believes the codec_mask read from the register even if it's a read failure as I already showed.
This approach has least regression risk.
Yes, but it assumes that HD-audio is really non-existent.
I really don't know any good approach to address this. On Windows, HDA PCI is "hidden" until HDMI cable is plugged, then the driver will flag the magic bit to make HDA audio appear on the PCI bus. IIRC the current approach is to make nouveau and device link work.
I don't have the full context of this discussion, but the kernel force-enables the HDA subfunction nowadays, irrespective of nouveau or nvidia or whatever:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/driv...
Cheers,
-ilia